Our sales engineer, Paul DeWys, gave this presentation on Part Design for 3D Printing at 3DExperience World / Solidworks World 2020. Through the use of example parts he covers how to optimize your 3D CAD design for both prototyping and mass manufacturing on 3D Printing Equipment.
My name is Paul DeWys. I own DeWys Engineering and Forerunner 3D printing. We’re located in Western Michigan, by city of the Grand Rapids is where we’re by. A little bit of background about myself and the companies. In 2009, I started the engineering portion of our business out of my college dorm room, pretty much. I was working for tool and die company and saw an opportunity to get hired to work remote from school. They hired me and the first thing I did was went out and bought a seat of CATIA, I know, and ran CATIA for that first year and then very quickly bought a seat of SOLIDWORKS, and from there, transitioned into doing almost probably at this point, our firm probably does 90% of our work in SOLIDWORKS. From 2009 to 2016, myself and a team of engineers, we grew DeWys Engineering. Today, we have customers in automotive, aerospace, a lot of automated equipment, agriculture, foundry, furniture and some new product development sprinkled in there for good measure, so pretty diversified, mixed in what we do. In that 2009 to 2016 timeframe, I was doing a lot of product development for a company. We were making cellphone cases that had tasers built into them, of all things. That required a lot of 3D printing. I found a service bureau the next city over from us and started sending all of our work over to them.Being that I’m a sales guy, I like to talk, I would go over there and pick up parts from the guy who owned it and he was a sales guy, he liked to talk, so we’d go and just talk for an hour or two every time I’d pick up parts. Over the course of six months, found out that he didn’t really have a succession plan for his business or anything like that. He was just getting close to retirement and didn’t really know what he wanted to do. Just offhand, one day, I just said to him, “Ross, when you’re ready to sell this business, you should give me a call. I’ll buy it from you.” He goes, “Well, maybe I will,” and I said, “Okay.” Then two years went by and I completely forgot about that conversation, and then one Tuesday morning in 2016, I get a phone call and it’s, “Oh, it’s Ross Gates. I’m done. I’m selling it. Do you want it?” I’m like, “Hello, Ross. Sure, I’d love to buy your business.” I hang up the phone, and then, I google, “How to buy a business,” because that was pretty much where I was at. Thankfully, Google, just like in most cases, had lots of answers and advice. By the middle of summer 2016, I bought the assets of that 3D printing company, which at that point, were two SLA machines and moved them over to where DeWys is at and started up Forerunner 3D printing. That’s kind of the quick and dirty short version of how I got into the 3D printing business and where we came from before that. Shortly after getting into the 3D printing business, it became clear that end-use parts, not just prototype, were possible with these machines, but you needed to design for them, just like you would for injection molding or stamping or sheet metal fabrication. Generally when I say that, the first thing that people will respond to is, “But I thought, with 3D printing, you had unlimited design freedom?” You do. You absolutely have unlimited design freedom, but just like with any other process, if you optimize your design for 3D printing, there’s lots of cool unlocks that you can get from doing that. One of them is isotropically stronger parts. What does that mean? Well, typically, 3D printer parts are strong in X and Y but weak in the Z direction, weak with the layers. Well, there’s ways around that. You can design around that to make your parts isotropic, where you have strength and all the directions that you need and you might sacrifice strength in a direction where it doesn’t matter. Less post processing time. Anyone here who’s ever used anything from a $500 MakerBot FDM machine, all the way up to $500,000 3D Systems SLA, everyone knows when you take that part off the build platform, half the work is done. Now, you got to take all the support off of it. You can have tons and tons of time and frustration and scrap parts from dealing with support. There’s ways you can design around that. You can design it to have no support or you can design it to have minimal, easy to handle support. That’s another thing to think about when you’re looking at additive. Then added functionality and unique features. 3D printing allows for things like integrated springs, printing assemblies as a single part, trap components, non-machinable, non-injection moldable and non-stampable features. Because you do have that crazy freedom that 3D printing affords you, you can do some really wild stuff. That’s what I’m going to show you here today.Then lastly lower cost. Anyone who’s ever dealt with 3D printing over the years, especially if you don’t own the equipment yourself, if you’re coming to a service bureau or an additive manufacturer like us, will know 3D printing can get eye-wateringly expensive in a very, very short amount of time, depending on what you’re trying to do. Well, again, if you design your part with 3D printing in mind, there’s ways to get around that. There’s ways to take apart that might cost $1,000 per piece and drop that down to $250 per piece by getting a little creative with how you design it. The following examples are going to be parts that were either specifically designed for 3D printing or parts that we took in from customers and ran through our engineering department to redesign them to be 3D printed. I’ll just throw this out there, guys, like I’m just going to crank through this. If you have questions, raise your hand, but if I’m not looking at you, feel free to just be like, “Hey, Paul, I have a question,” or, “Hey, I have a question.” Otherwise, we’re just going to keep cranking right to the end. First thing I like to do in each section, I like to do a little technology overview just because there might be people in the room that aren’t familiar with what the equipment I’m talking about. I’m going to summarize the three piece of equipment we’re going to talk with a little video here at the frontend of each one. The first technology we’re going to talk about is SLA, stereolithography. This is the first 3D printing technology that was brought to market. It was brought to market in 1990. Essentially, you’re using a UV curable resin down in that vat and you’re using a UV laser. Wherever that laser touches the top surface of that vat, it’s going to cure between a 1 to 10 thou thick layer of that material, depending on your settings. Layer by layer, that laser hardens up each layer material, and then, you recoat, harden up the next layer. Recoat, harden up the next layer. This technology has been around for a very, very long time in the world of 3D printing. There’s still a lot of great applications for it. It is a little bit limited by some of the material science and stuff like that. A lot of people use it just for prototyping, especially if you’re prototyping big plastic enclosures. You want to check stamps, you want to check screw bosses, things like that, but I have an application where we actually used SLA for an end-use part. Like I mentioned, about half of what my engineering company does is automate the equipment design. We had a customer that came to us with this part or a machine that required this part. The challenge, design a block that could route both high pressure air for blow off and a strong vacuum to remove blown off dust in one part. We used a computational fluid dynamics, CFD inside of SOLIDWORKS and that analysis had guided the designer to angle the high-pressure air holes in a very awkward way for manufacturing. This area right here on the top, we’ll get a section view of that in a second, it’d be very difficult for traditional machining to put those holes in there, if not impossible. The block also had many internal air and vacuum channels that would have required many setups in the mill. Also, we would have had to gun drill this block and actually turn it into an assembly, so there would have been a lot of places in there. We have sharp corners where eddies could have formed and you could wind up with a lot of materials trapped inside the block not easily cleanable. Due to all this, we designed it specifically to be 3D printed in so most watershed on an SLA 500. Then because we needed it to stand up to a shop for environment, I guess that SLA is aren’t known for their strength. We actually encased it in a stainless steel block. The SLA never came in contact with the strip media that was rolling through it that we’re blowing that dust off of and then vacuuming it into this block. Stainless steel took all the wear. The block was just really for air and vacuum management. All right, we’ve got a couple different views of the block here. 3D printing allowed the high pressure air holes to be arrayed at very specific angles and locations called out in the CFD. You can see here. Actually, this is even a better view right here. They’re arrayed across the top to fan out and hit the entire bottom of the substrate that we’re blowing off. Again to do that in traditional machining would have been extremely difficult. The four vacuum chambers had to or had the ability to be tapered to a very specific mouth size to do optimum draw based off of analysis and everything like that. You can see these purple chambers right there, those are actually vacuum chambers. You’ve got high pressure air in the middle, you’ve got vacuum to either side of it. Again, we could get very, very exact and how we want those vacuum chambers to be created. After placing all the HPA ports and vacuum chambers in the block, we then plumbed it. We have all of our air and vacuum coming in through the bottom. Once we had those chambers in place, we just routed all of the supply lines through unused areas of the block completely. Wherever we wanted to put it, we could put it which is really handy. One of the things that is kind of important to point out with this one is thinking ahead when you’re designing about having a trapped volume. We can’t get support out of these internal chambers after we print it. You want to think ahead and use things like high angles. That’s a 60-degree angle for the roof of those vacuum chambers. Anything over 45 degrees in 3D printing is self-supporting. It doesn’t need support. That means we don’t have to worry about anything being in those chambers. SLA is a liquid process. Whatever liquid resin is trapped in there when we’re done, we just hit it with compressed air, it blows it right out and you’re left with an empty clean vacuum chamber. Same with the array of holes across the top, you’ll see that that’s an arch. Think back to basic engineering when you’re in school, you build an arch. It’s self-supporting. Same thing here. We don’t have to have a bunch of support inside of that chamber that we have to figure out how to get out of afterwards. Then, all of our passageways, these purple and teal passageways, they’re all circular. Don’t make it square. Don’t put a flat top. You have to have support in there. It’s that kind of stuff that if you think ahead in your design phase about how you’re doing the internal structure, you don’t have any support to deal with, so you just completely unlock a whole new design that you can do with 3D printing that you couldn’t do with any other process. Let’s see here. Then lastly, you notice this has a nice flat bottom on it. The part has a nice flat bottom. Very, very easy to build support, up off of the build platform, build support up to that bottom. Rip it off the build platform when you’re done printing it 30 seconds with a piece of sandpaper and that is all the postprocessing that this part needed. I’ll tell you this as someone that owns a 3D printing company, yes, the machines are expensive, but manpower is right up there too. I have to bill out $60 an hour for a modelmaker. If I have to have a modelmaker sit here and sand this thing for four or five hours, you can do the math. You just increased your part price by that much per part. Anything you can do to reduce sanding or reduce bench time is going to go right back into your pocket. All right. Oh, one last thing, a SOLIDWORKS tip for you guys, Draft Analysis. I’m sure anyone who’s done anything with maybe castings or with injection molding, Draft Analysis is used for parting line analysis and things like that. Well, you can also use it in situations like this where you go, “Hey, what areas inside of my block are violating that 45 degree rule or violating that arch rule?” You can use Draft Analysis to very quickly select the bottom plane of your part, turn it on, and boom, everything’s green or everything’s red. You know exactly what your problem areas are. Draft analysis is a really handy SOLIDWORKS tool for evaluating this stuff. All right. Take a quick sip here. Onto the next technology. This one is somewhat newer. It’s HP MJF. If anyone here has ever messed around with the old 3D Systems or DTM laser sintering machines or EOS machines that use a laser to sinter powder, this is a new spin on that. There’s no lasers involved in this. This is HPS take on SLS. It’s called HP MJF, Multi-Jet Fusion. We have a print bed, and on our print bed, we’re printing this gear. We just finished a layer. We’re getting ready to start the next layer. First thing the machine does, it spreads 0.0003 of an inch thick layer of nylon powder, white nylon powder across the top of the part. Then it comes over and it coats the entire bed in one pass with fusing agent and detailing agent. Detailing agent gives you really crisp geometry, crisp sharp edges. The black fusing agent, when exposed to high-energy IR light, like it is right here, that black fusing agent absorbs all that IR light. It drives the temperature up in the blackened region of the print bed and it actually melts and sinters all those nylon particles to each other and to the layer below it, but that detailing agent prevents it from sintering to any of the white powder around it. You think about it, you got a black car and a white car in a blacktop parking lot in the summer, black cars are always going to be way hotter than when you get into the white car. We have a white powder bed and we have a black part region. The black area gets way hotter. The white powder around it reflects all that IR energy and does not melt. The advantage to this over SLS really comes down to speed. You can run this machine way faster than you can run an SLS. That’s why this is one of our favorite machines for low volume manufacturing. The example here, ratchet safety cover, the challenge take an existing safety cover for a high-speed ratchet assembly tool and redesign it from machine Delrin plastic to a part that is 3D printed out of nylon 12. The decision to move from machining to 3D printing was driven by two factors, lead time and cost. The annual usage for this part is between three and 500 units and the diameter changes with every run. The customer could not justify an injection mold and then they were machining them for that reason. The lead times and machining costs had steadily increased for the CNC machines used to produce these over the years to the point where they just couldn’t justify it anymore. Well, they could justify it, but the owner of the company was so frustrated by it. He was open to anything that would get him away from CNC machine plastic. We were working on another machine design project for him. We came across this when we were working on it. We said, “Hey, give us an opportunity to see if we can convert this over to an HP MJF part for you printed out of nylon,” and so we did. One thing, Delrin has a little bit more … Stretchy is not the right, but it can elongate a little bit more than the nylon. Nylon is a little bit stiffer. Originally, it was a solid diameter all the way around and there’s a detent inside of there, to detent over the ratchet. When we originally printed it, we printed it solid and we went to press it together with our arbor press, the nylon part would just explode. It would just crack, whereas Delrin which stretch a little bit and so it would work just fine. What we came up with is, “Okay, well this isn’t working. Let’s petal the design,” essentially, think about petals of a flower coming open. All they needed was it to momentarily stretch and then snap back over to do that detent. With 3D printing, I’m going to say it once, I’m going to say it 1,000 times in this presentation, complexity is free. It’s size that will cost you. In this case, add these slots and there’s not like a separate setup. It’s not like it just went from a three to a four-axis part. It doesn’t matter. Complexity is free. We petaled the design and it worked great. It solved our cracking problem. The next thing was, once the customer saw the original design, they said, “Oh, this is great,” but now, we have a guy going through and literally writing in Sharpie on every single part what the size is. Would it be possible for us to actually print the size of the ratchet being held inside of it to the outside? Again, no problem. Complexity is free. We put the text. We put the size on the outside of the part and it doesn’t matter. It literally doesn’t cost them anything extra to print text in. Anytime you can add text, logos, texture, anything like that to a 3D-printed part, it’s not like machining or injection molding where, “Oh, it’s injection molding. We put a logo on the space. Now, I got to add a slide to get that part out of there.” No, it doesn’t matter. It literally doesn’t cost you anything extra to add those features to your parts. A little trick though, if you’re getting into a product where you’re going to be iterating, a whole bunch of different versions of it and you’re going to be constantly changing the text on the outside of the part, you can take and you can link the text inside the SOLIDWORKS model in the sketch. You can link it to a field in your property tab manager. We use a start part. We’ve done hundreds of different sizes of these. We have a start part that we start with every single time and it’s got all of this already built into it. When we pop open our property tab manager, there’s literally a field that just says notes and we type the size in there. When we hit rebuild on the part, it literally propagates it right on the side of the part. Afterwards if anyone wants a copy of this PowerPoint, feel free to come up and I’ll give you the PowerPoint. It literally steps you through exactly how it works up here, but for sake of time, I’m going to just keep it moving. This is a great way to do mass text customization and not be in there editing sketches every single part. It’s very easy to do and quick. Let’s see here. Another example here. Example, end-of-arm gripper fingers. The challenge, reach into a very tight space and an injection mold and place a part for overmold. Due to the number of grippers required on the end-of-arm tool, they needed to be lightweight. The grippers also needed to house vacuum cups. There would be no room to route vacuum lines along the outside of the gripper fingers. They needed to be routed through it. This is actually one where we originally did all this like we would normally would, machined aluminum, typical grippers and things like that, but we kept having this issue where the pick and place robot would go into the mold and they would actually catch an air line on, I think it was a lifter and it would snag every just enough to make it a problem. Every 10,000 cycles, they’d snag and it would break the air line and then you’d be dropping parts and it would be mess. The customer said, “We got to figure out how to get this air line out of the way,” and we said, “Well, shoot, let’s make a 3D-printed gripper finger and we can kill a bunch of birds with one stone here. We’ll actually route the air line through the inside of the gripper finger.” Specifically, I’m talking about this one here in the center. These are just some examples of other gripper fingers we’ve done over the years. This is the SOLIDWORKS model. This actually shows you know the solid part or the part. Here it is with a section cut through, it ghosted and then here it is with a true section, so you can see the air lines that are going through there. One of the most beneficial features of 3D printing is that it can print features that are not possible or would be very expensive through traditional manufacturing which in this case would be CNC machining. Coming at this detail, having to gun drill down through it, plugs in, things like that, in this case, just do a sweep cut through there and you get your air line right inside the part. The gripper fingers need to have vacuum cups placed in them due to space constraints. We already talked about that. A tip, for any time you’re doing an internal passage through, in this case an MJF part but even like something like an SLS would be the same way, we like to keep our internal passageways at least 3/16 in diameter for depowdering purposes. I’ll touch on this again and a little bit with another example, but when we’re done printing, the part is full of powder and we have to get that powder out sometimes. Well, we’ve had customers that want us to print a 25 thou air passage going all over the place inside of a part. Well, the part gets so hot that even though you’re using detailing agent to try and keep that powder inside of there from centering, you’ll wind up with an area that got too hot and that nylon will melt inside that channel and you’ll never depowder it. You essentially have a little plug somewhere in that route. We typically say, “Print at 3/16, he bigger the better if you can, and then neck it down at the very end,” where we can go in with a brush or even a steel punch and pop that that last little section out of there, and then, you can put in your threads or you can just leave it as a nozzle or something like that. If you’re doing a powder-based machine always be thinking about like, “How am I going to get this powder out of the part? Then more importantly, am I going to wind up going too small and creating a plug inside of this path?” something to keep in mind for powder-based machines. In this application, another thing, was adding texture. We had a problem with this dropping part sometimes. We actually designed in a super aggressive texture on the inside of those gripper fingers, so you can see it right there. That texture is very, very aggressive. Again, it would have been an EDM burn to put that into a metal detail or a ton of time with a little itty-bitty 10 thou ball and mill and they’re trying to chew out the bottom of that texture. Again, it didn’t cost anything extra to do this. It’s 3D printing. It’s not going to take more cycle time or take more setups. You can include stuff like that and it’s not going to really kill you on cost. Another thing I mentioned was weight was a consideration. When we did these out of aluminum … I’m sorry, when I took this same part and set it to aluminum for material, it was 0.41 pounds per gripper finger, okay? In nylon, it was 0.18 pounds per gripper finger. If you’re dealing with like cobots, like the small cageless robots or something like that, weight is a huge constraint for those robots. In some cases, every gram can count when you’re dealing with those small robots. We’ve had a ton of use cases for nylon parts for doing end-of-arm tooling for those and doing all of our internal air line routing, anything to cut down material weight on the end-of-arm tools. The end result was the gripper fingers that you’re looking at here. We tried to do these with traditional manufacturing. We really couldn’t have done it, but if we tried to get close, it would have required a couple setups in a three-axis machine or doing a five axis CNC. In this case, we were able to do these and turn them around in two days and the cost to our customer was $300. Additive for the win on that one. Shifting away from automation, shifting more towards some consumer product type stuff. Example, cellphone case/credit card case. The challenge, design a cellphone case that also holds three credit cards. Due to the design of the part, it had to be produced on additive manufacturing equipment. It wasn’t moldable. The finished case needed to be manufacturable for $15 a piece to make it an economically viable product. Then also again, keeping that manufacturing cost down, to cut down on manual assembly and hardware costs. We didn’t want to have to do any assembly or attaching any hardware to this after we were done. We want to be able to depowder it, color it and ship it. Here, this is an iPhone, I don’t know, iPhone 11, whatever. I’m an Android guy, but whatever the most recent iPhone is, that’s this version. This is another version over here. If anyone wants to steal my identity at Topgolf, knock yourself out. This is for a much smaller phone called a Light Phone, which is a really niche cellphone that is out there. Again, we wanted to develop cases for these really niche phones, but we didn’t want to spend any money on tooling because, “Are we going to sell one of these or are we going to sell 10,000 of these?” I didn’t know. I wasn’t about to go drop $30,000, $40,000 on tooling. Oops, there we go. This is talking about a couple of the features here. You can see right here, you can see there’s these green bodies just floating in space. Those are actually fingers that are actually mounted into the case further back and they flex. They’re actually springs. Those are what you slide the cellphone or slide the credit card into and then it detents past the credit card and locks it in place. We needed to leave gaps around the outside of that feature, so it didn’t weld itself together inside the machine. If we had it face to face, it will just print it as a solid part. You have to leave gaps inside of any 3D-printed assembly to keep the parts from welding together. Then also for depowdering, we have to get all of that nylon powder out of the part after it’s printed because it’s all sitting inside of there. You need pads to allow that powder to come out when you use things like compressed air, blowoffs or bead blasters, tumblers, stuff like that. The rule of thumb that we always work with MJF technology, you need at least a minimum of 0.00001 of an inch gap between faces to allow them to not weld themselves together inside of the machine. I would say the same thing applies for SLS technology as well. You have to leave at least a 10 thou gap. If possible, we like to leave 0.00015 just to feel a little bit better, but that’s the rule of thumb 10 to 15 thou gap between parts. Then like I said, we have to think about how the powder is going to escape. That’s important. Then, as far as the spring goes, I’m going to back up here a second because it’s easier to see right here. Where’s my pointer, there it is. These fingers right here, here and here. You can see how they flex out of the way and they allow the card to slide out. You have the same fingers built into this iPhone case that we’re looking at right here. I’m talking about these spring features. Those are what I’m talking about right there. You’ll notice, those spring fingers actually come through all the way to the inside of the case. Now, you’ll never see that because the cellphone is going to cover that up, but that’s specifically done to allow for ease of depowdering, to blast that compressed air through there and not have a trapped volume that we can’t get compressed air into the strip that powder out. Again, this is a section view of those fingers that we’re just looking at. We do a lot of fun stuff with essentially printing nylon 12 parts and using it as like a spring. Nylon 12 is very flexible when it’s thin like this. We’ve also done a lot of cycle testing up to 100,000 cycles and not had these springs wear down on us. They hold up to that amount of use. A lot of times, people ask me like, “Well, how do I design a spring feature and additive?” The best rule of thumb for that is it’s a lot like if your design, a snap feature or a spring feature into injection molded part, those are generally good designs to start with. If you’ll look online, you can find all kinds of people showing different injection, molded springs and stuff like that, but then plan on two or three iterations, because it’s not going to line up perfectly with how an injection molded part performs. We generally say, “Plan two or three different ideas. Find the one that works and then iterate that idea further.” That’s generally how we go about developing springs for production on additive equipment. Another thing here is try to remove excess material wherever possible when cost is a factor. This will save you raw material cost. In this case, that was done by a honeycombing the part. You’ll see this version right here is solid and that’s a window that you would see the credit card through. Over here, we’ve honeycombed that same region. We honeycombed not only the outside. We actually honeycombed all the way through to where the cellphone would be. That’s just to cut material because material is money. Anything you can do to cut material out of your part, that’s just money in your pocket. Another thing is we can easily run compressed air through there to depowder that credit card pocket inside of there. Again, if I got to have one of my modelmaker sit there with dental tools and clean out the inside of that, that’s the cost. It’s up here. If I can throw these into a tumble the blaster and let them sit there and tumble for 15 minutes and pull them out, your cost is down here. Again, think about the human factor when you’re designing for additive manufacturing for production because it does add up. The question is, what’s the tradeoff between the design time that it takes to think ahead and do this versus how maybe you traditionally would do an injection molded part versus the time it takes for a modelmaker or someone to clean up these parts after printing? I would say, if you’re just doing a prototype, if you’re prototyping a product, obviously don’t make any of these changes. Draw the product that you actually want and we’ll do it, but if you’re considering, “Hey, I might want to make 2,000 or 3,000 of these and go right to production with a 3D-printed part,” absolutely, this is totally worth the time investment. Another thing I’ll say is, like I said, I have an engineering department. For the first year of the business, they were just doing engineering work and we were just doing 3D printing work. Then after a year, we started to realize like, “Oh, my god, there’s all these opportunities. If we could just take the lessons we’ve learned from here and teach them to our engineering staff,” where probably six months of training which was pretty much people would be like, “Hey, Paul, you come look at this and look at it and say, ‘Yup. No, here’s what I would change. Here’s what I wouldn’t change.'” If you’re using like a big online service bureau like Xometry, they’re great guys, but if you’re using Xometry or Protolabs or any of those places, a lot of times, they just want to print parts their volume. They just want, “Give me your part. I’m going to give you an instant price and I’m going to give you a part as cheaply as possible.” If you want to really get into this, I would really recommend look at smaller service bureaus, guys like us. CIDEAS is another great one to work with. InterPro out on the East Coast, another great one to work with. There’s a lot of mid-tier service bureaus that have application engineers who would love to get on a go-to meeting and be like, “Here’s, what I would …” If you call them up and say, “Here’s the part I want to make. Please help me figure out how to make it as cheaply as possible,” you’d be surprised, but they will sit down and say like, “Think about this, think about this, think about this.” If you’re sitting here thinking like, “How can I ever bring this into my organization?” Find a really good small or to medium-sized service bureau that isn’t just interested turning around volume and they’ll teach you. They’ll teach you for free. Well, you’re going to buy parts from them, but well, pretty much for free. Did I answer your question? The question was, because the credit cards are going into those pockets, do we print the parts vertically for strength or for work purposes? In MJF, no. With MJF, we lay everything down on the print bed and then we nest volume and we nest up in height just like you would on SLS machine. If I was trying to run this on like an SLA machine or an FDM machine where I have to have support, it would completely change that answer. I would probably take an actually stand it up on this end right here, so that will flip this part over 180 degrees and standard up on that face to try and make no support happen inside of that credit card pocket. There would be support on the other side of my part. In this region right here, there would be support, but there wouldn’t be any in the area that would be really hard to get out. Depends on the technology you’re working on.
I got something you’re really going to like here in a couple of slides. The question was surfaces, surface finish. Usually with additive, it’s either a really smooth surface finish or it’s maybe a rougher surface finish like you’d find on an SLS or MJF machine. The question is, what about like leather texture? What about knurling, things like that? I’ve got a slide specifically talking about a SOLIDWORKS feature that addresses that question. This product specifically couldn’t be produced any other way than MJF. That was our whole point with this project, was we wanted to design a product that would be so tailored to the MJF process, you couldn’t make it another way. That being said, we have a bunch of other products where, we’ve used 3D printing as bridge, a bridge to get us to production. Generally, if you have a part that will fit in the size of your hand and would require, let’s say, two or three slides or lifters and an injection mold, we generally see that breakeven point somewhere between 5,000 to 10,000 units is where the tooling starts to make more sense than the 3D printing. Good questions. I like questions, please ask more. The question is, do we run issues around lead time for 10,000 of these? I want to say we can do 150 or 200 of these per build and we could do that every single day. If you needed 10,000 in three days, yeah, I’d have a real problem. There are huge service bureaus out there like Forecast 3D out in Carlsbad, California runs 27 HP MJF machines. They’ve got customers that I’ve heard they’re running tens of thousands up to 100,000 parts a year for so. There’s some real production use cases out there where people are running production on specifically HP MJF equipment is the big one.
Moving on. Next up is FDM. This is a 3D printing technology that most people are most familiar with. This is your MakerBots. This is your Fortuses, your Dimensions, all the Stratasys equipment. It’s essentially a CNC-controlled hot glue gun. You run your ABS wire or PEEK or nylon or whatever material in and you’ve got a hot end and it’s going to lay down like white support material and it’s going to lay down black model material. The nice thing about these machines is they can get extremely large. A Fortus 900, off top of my head, I think it’s like a 24-inch by 36-inch by 36-inch build volume. You can get extremely large with these parts and it’s an end-use thermoplastic. I see a lot of people using these for either big injection mold parts like we’re in Western Michigan, so automotive, big interior dash components, headliner components, outer trim, bumper components, things like that.
A lot of med device companies may use it for large like hospital beds and things like that, but also a lot of tooling, so a lot of vacuum forming tooling. People will use this instead of a red board, CNC-milled red board tooling, just all kinds of applications for FDM. Again, one of the older more legacy technologies, but still very actively used today. This is a specific example of one of our parts here. Example, tape applicator hand tool. The challenge, design and 3D print a series of ABS plastic hand tools that can be used to guide the application of tape onto windows during assembly. The tools are used on a daily basis and need to be strong and were resistant. There is a large range of window sizes and designs. That coupled with the cost to set up CNC machines for each size tool require the need for the finished cost of the tool to be $100 each. That just made traditional CNC machining just too expensive. The mix was so high and the volume was so low that they just couldn’t get their prices that low. All of this was literally done. This wasn’t done on one of our big Fortus machines. This was all done on like a desktop 3D printer. Something that I’m sure a lot of you have in your offices, a Markforged, an AXIOM, a MakerBot. That’s what we do all these on because the price is so low on the materials. I want to broke it. There we go. The upper right hand picture, that’s actually the finished part right there that I’m going to be talking about, and then, the rest is the SOLIDWORKS model showing how the part actually goes together. Again, different 3D printing process, but you still have to think about adding clearance around components that are going to be trapped inside of there. Now in this case, it’s this blue roller which is actually colored white up here, making sure we have enough room inside of that pocket for that roller to sit in there and not be tight and not get bound up. For FDM, we generally leave about 25,000s around the exterior part of mating components to make sure there’s plenty of room for them to run smoothly inside of there. Allow for … Let’s try that again. To allow for the nice round holes that you need in a lot of situations, you always want to try and orient your critical holes straight up in the Z direction and this applies for actually any 3D printing technology out there but specifically for FDM. If you have a hole that’s on its side, so the machine is building support inside the hole and that’s what’s creating the whole feature, it’s always going to come out egg shaped. It’s never going to be perfectly round. If you want a perfectly round hole pointed straight up in the Z and it will be extremely round every single time. Otherwise, plan on thickening the wall and then running a reamer in there to true that hole up if you can’t lay it down and print it straight up in the Z. Let’s see here. Another design consideration here was you’ll notice that we have these big flat surfaces on the sides here. The reason for that is, again, support. In this case, this will print with zero support on our FDM printer. That means there’s no support to break off. There’s no support stubble to sand off. There’s literally no modelmaking time associated with this. It’s just putting the parts together when you’re done. By leaving a nice big flat, we get that zero support because we’re building it right to the print bed and also you actually get a really nice like high polished surface finish on those sides, which is where someone in this case is going to be gripping. They wanted it to have a nice smooth finish for people’s hands. You will wind up with a pretty nice burr around the outside when you’re doing FDM printing. Just run around it with a deburr tool. Zip that burr right off there and you’re done. Again, anytime you’re doing FDM printing or SLA printing, the bigger flatter surfaces that you can put down towards the bottom the easier the supporting and then finishing out the part is going to be. Let’s see here. Then lastly, these feed ramps, which is where the tape actually, double-sided sticky tape, goes through as we’re applying it to the windows, we wanted those ramps to be as smooth as possible. We didn’t want like a stair-stepping effect from the layer lines. Again, by orienting it this direction, the extruder is running along that edge right there, so your layer lines actually go in the direction of which the tape is going to be moving through there. If you have layer lines going across your direction of movement, you’re introducing friction into that movement, whereas if your layer lines go along it, it actually helps because you’ve got little air gaps in there and so you’re actually substantially lowering the friction by pointing your layer lines through the ramps of your parts, around these parts. Again, when you’re designing, think about layer lines and layer direction and there’s a new feature or newer feature in SOLIDWORKS here, I’m going to show you in a second that helps visualize that really well. All right, so 3D texture. This is a tool inside of SOLIDWORKS. If you go up to the little help window on SOLIDWORKS, you can change it to commands. You type in 3D texture, and boom, it will pull up the 3D texture tool because I don’t actually know where the button is to be honest with you. John, can you tell where the button is? I don’t know where the button is. Just search for it. That’s the best way to find it. If you play around with SOLIDWORKS rendering at all, you’ll notice that I believe at the very bottom of the tab for all your different finishes and colors and everything like that for real view graphics. There’s actually a textures button at the bottom. Inside that textures button, I think it might even be called 3D textures, there’s all these grayscale images sitting in there. For the longest time, I was always like, “Well, this is dumb. I can’t do anything with this. What’s the point?” Well, they introduced this tool. Now, you can apply these grayscale images and then use this 3D texture tool and you can actually texture apart. This is what it looks like in SOLIDWORKS with the texture applied. This is what it looks in SOLIDWORKS after you run the 3D texture tool. This is what the actual printed part looked like after we 3D printed it. Yes? The question is, by default, will the texture apply to the outside of the surface and not grow your part? No, the texture will grow your part. Good question. It will definitely make your part bigger. There’s a whole bunch of sliders and fun buttons that you can click in this toolbox right here that you can make the texture more aggressive, you can make the texture more subtle. General rule of thumb though for specifically HP MJF-printed parts, your texture has to be at least 35,000s tall for it to show up on your part. Anything less than that, it will be there, but it won’t look great. 35 thou and bigger, that texture will pop out really nicely. Do I see some other hands? No. 3D texture, very, very powerful. I highly recommend you just go and play with it. There’s some really good videos on YouTube of people using it. Definitely check this out if you’re trying to do anything cosmetic with your parts and you want to hide the traditional 3D printing texture. I would recommend against 3D texture for things like FDM-printed parts and SLA 3D-printed parts. I would stick to things like PolyJet, HP MJF, and SLS machines. The SLAs and FDMs, I don’t really think have the resolution to do this on a sidewall, maybe on a top surface, but definitely not on a sidewall condition. That’d be a vertical wall. This is by far one of my favorite things. Like I said, we do a lot of automated equipment. Literally last night I had a customer send me a part. It’s a little block and it’s meant to hook into at 8020, which is an industrial erector set for lack of a better term. We use 8020 for machine guarding. Anytime you walk through a factory, there’s all those nice big Lexan windows to keep you from reaching in and getting killed by a robot. That’s pretty much all 8020 or Bosch that is holding that together. This customer designed a little block to hook into the 8020 channel, and then, he put a 1/4 x 20 hole through the block. He’s going to use these blocks to attach Lexan to his machines in a very specific way where he couldn’t find a mount on the market to do it. I’m sitting there looking at it and he wants to order a thousand of these. That means we’re going to print a thousand of them. Then, one of my modelmakers is going to sit there for like a week with a hand tapper, like a hand tap and tap a thousand holes into these parts. Again, it drives the cost way up. Before we knew that we were going to need to tap these, it was like a $3.50 part. Then when I found out that I was going to have someone sit there and tap all these holes, it jumped up to a $6 part. What we’ve found over the last couple years is when you combine Hole Wizard and the Thread Tool inside of SOLIDWORKS, you can print threads. Now specifically, we always do it on our HP MJF machine, that nylon machine, but we’ve also done it a little bit on FDM and a little bit on SLA and a little bit on PolyJet. It does work on other technologies as well. You can’t go under a 1/4 x 20 in thread size or an M12 in metric thread size. Anything smaller than that, unless you’re running a PolyJet machine, you just don’t have the resolution to resolve those threads, but with a 1/4 x 20 and up you can print the thread directly into your part. With HP specifically, it’s insanely strong. This is a test block that we have right here. We put onto our pull tester. So that’s a 1/2 x 13 thread size. That’s literally an eyeball downloaded from McMaster-Carr. They already have the threads on the outside of it. Then, we pull up the Hole Wizard. We put in a 1/2 x 13 tap drill size into the block. Then, we grab our Thread Tool. Again, there’s a bunch of great YouTube videos that will walk you through how to use the Thread Tool way better than I do up here in front of you. I highly recommend look up how to use the Thread Tool on YouTube. You run that thread down in there, and then, you actually print the thread. This thread right here, this broke at over 900 pounds intention and it wasn’t the thread that actually pulled out of the block. The eyeball actually broke where the cross section neck down at that first thread. We were able to take a punch and spin the broken portion of the thread out of that hole and put a fresh one in there. It didn’t elongate the threads or anything. When you’re using the correct 3D printing equipment and you’re printing threads, they can be insanely strong. Thing to keep in mind though is if you’re running a metal fastener into a plastic thread and you’re taking it apart and putting it together, over and over and over and over, eventually you will wear those threads from metal and plastic contact. The hack there is if you can, use a plastic fastener. Again, you go to McMaster-Carr. You can find tons of plastic fasteners, and if you have an application where you don’t need a ton of strength in your fastener, you’re just trying to hold something together, you can use a plastic fastener on a plastic 3D-printed part and those threads are going to last you forever. That’s a really fun SOLIDWORKS trick too is use Hole Wizard plus Threads and you can unlock some really cool design capabilities. This is another new one that we started playing with this last year, ran into … How are we looking on time, 10 minutes? Thank you, sir. What we ran into last year is we’ve got customers now that are designing specifically for end-use additive. What happens all the time is people will go, “How big is the machine?” You go, “Oh, it’s 15 x 12 x 15, or in the case of like an SLA, it’s 20 x 20 x 20.” Inevitably, they will design a part and it will be just a hair too big to actually fit into the machine without fail. Inside of SOLIDWORKS, I think this has been around a couple years, but they have this 3D print button. If it’s under file and 3D print, if you’re in the part, working tab. If you go there, there is a little 3D printer simulator. I had a customer told me about this actually and I first heard about it, I’m like, “Oh, great, so it’s going to have every type of MakerBot and every type of FormLabs and none of the stuff that I actually use.” Shockingly, they have a massive list of 3D printers. All of the ones I use are in that list. What you can do is up here at the top, I have this set to HP Jet Fusion 3D 4200. That’s the full name of our MJF system. Then, it sets the bounding box, and then, you can actually show your part inside the bounding box of the machine. As obvious as this sounds, this is massively helpful for people to your question who are new to 3D printing, who don’t necessarily know sizes off the top of their head. This is a great way without having to call your service bureau to figure out what size machine you’re actually … If you know what type of machine they’re going to run it on, you can check to see if your stuff’s going to fit even before you send it to them or you might have a conversation with them like I did with this customer of, “Okay, it’s pretty tight side to side, but if we tip it up 20 degrees, it’s going to make your part a little bit more expensive, but we can fit it in the machine without having to add cuts or splits or anything like that.” This is a really handy tool for just quickly analyzing, “Will something fit? Will something not fit?” Now, remember a couple slides ago, we’re talking about FDM. We’re talking about having your layer lines in there and trying to figure out what direction your layer lines are going to go in because you want a smooth layer lines in one direction. You can actually turn on layer height and show striation lines and it will actually put a texture onto your part. You can see what the layer lines would look like and how those lines would be oriented depending on how you have that part sitting in there. I’ve shown this to a number of customers. Now instead of just getting a step file and a quantity and a material, a lot of times I’m getting, a picture as well from the customer saying, “Hey, I really want my layer lines oriented in this direction.” This is a super easy way to start that conversation between you as the designer and engineer and whoever’s running the machine, whether it’s your internal guy running it or an external service bureau. This is a really, really handy way to visualize what those layer lines are going to look like and also to the cosmetic question about wanting to apply textures or something like that. Again, if you’re like, “How’s this part going to look with layer lines in it as opposed to a texture?” this is a great way to simulate that without having to actually get the part printed and then not be happy with the finish. Because again, if you can tell your 3D printing company, “Hey, don’t worry about sanding out all the layer lines. I’ll just take it as is,” you just cut your price by probably 25%. Well, that takes us to the end of my presentation. I’ve got a couple minutes left. If anyone has any questions, feel free to raise your hand.
There is a lot of talk online about 3D Printed part accuracy. Mostly what you will find being referenced by other 3D Printing services bureaus are the numbers that the machine manufacturers (OEM’s) give out in there user manuals. At Forerunner 3D Printing we wanted to put these numbers to the test and see what kind of accuracy we could really achieve with our equipment. F3DP is equipped with a Faro Edge ScanArm system and Geomagics ControlX software (through a partnership with DE, our sister company). The following are real inspection reports that were put together using our in house inspection equipment / process and parts that were built on our 3D Printers. To read a full PDF of each of the inspection reports shown on this page click on the accuracy heat map images below. Also, if you have a 3D Printing project that requires critical tolerances to be maintained, we offer additional in-depth inspection report services on 3D printed parts we produce for our customers, please inquire about this service when we are quoting your project. Before we jump into looking at inspection reports, it is important to make sure you understand the meaning of accuracy, precision, and tolerance as it applies to 3D Printing.
Let’s start with definitions: What’s the difference between accuracy, precision, and tolerance? For each term, we’ll use a target—a common example for unpacking these concepts—to help visualize meaning.
Accuracy is how close a measurement is to true value. In the case of a target, true value is the bullseye. The closer you are to hitting the bullseye, the more accurate your shot. In the world of 3D printing, true value equals the dimensions you design in CAD. How closely does the 3D print line up to the digital design?
Precision measures the repeatability of a measurement—how consistent are your shots at the target? Precision measures this consistency only; your shots could be hitting near the same spot every time, but that spot doesn’t have to be the bullseye. In 3D printing, this ultimately translates to reliability; can you rely on your machine to produce your expected results for every print?
Exactly how precise do you need to be? That’s defined by tolerance, and tolerance is defined by you. How much wiggle room do you have in your application? What’s an acceptable variance in the closeness to the measurement that precision is hitting? That will depend on your project, for example, a component with a dynamic mechanical assembly will require tighter tolerances than something like a simple plastic enclosure. If you’re defining a tolerance, you’ll likely want accuracy too, so let’s assume we’re measuring precision of shooting at the bullseye. Earlier, we defined the shots on the target pictured on the right as not precise.
However, if your tolerance range is fairly wide, it may be okay. The shots aren’t as close to each other as in the target on the left, but if the acceptable range of precision is the distance of ±2.5 rings, then you’re within spec.
There are a variety of factors to consider when thinking about accuracy and precision in 3D printing, but it’s also important to identify your specific needs. For example, a precise-but-inaccurate printer may be the best choice for some applications. A low-cost fused deposition modeling (FDM) machine will produce less accurate parts, but for a quick and dirty proof of concept model for an engineering meeting, it may not be important for the model to exactly match the CAD design. On the other end of the spectrum, if you are running low volume production on an HP Multi jet fusion 3D Printer, the parts must be accurate and precise so they function consistently from part to part with out fit up issues at final assembly.
The follow reports are intended to give you real world examples of 3D printed parts and how closely we were able to print them to there original CAD designs. As we have more projects to share, our goal is to continue adding content to this page.
HP Multi Jet Fusion (MJF) produces parts with high accuracy and can print designs with complex geometry. The MJF printer lays down a layer of material, then sprays fusing agent on the areas that need to be melted on that layer and detailing agent around the perimeter of the areas that have been coated with fusing agent to allow for fine details to be produced. Due to the high heat used to melt / fuse the part material warping and non uniform part shrinking can occur if the build chamber is cooled too rapidly. To restrict the likelihood of parts warping or shrinking after being printed MJF 3D printers are coupled with a standalone build unit cooling station. This system is used slowly cool the parts after they are built in the MJF 3D printer (generally for 50% of the time that the build took).
SLA (stereolithography) printers use a laser to UV cure specific areas of a resin tank to form a solid part one cross section at a time. These cured areas however are not at full strength until post processing with UV. Because of this and the angle and orientations that SLA parts are typically printed at, sagging of unsupported spans can occur.
As one layer is built up at a time, this effect becomes cumulative leading to the dimensional discrepancies sometimes seen in tall SLA parts. Dimensional discrepancies can also occur because of the peeling process used by some SLA printers. The pulling force during the peel process can cause the soft print to bend which again can accumulate as each layer is built up.
Resins that have higher flexural properties (less stiff) are at a greater risk of warping and may not be suitable for high accuracy applications.
Material jetting is considered the most accurate form of 3D printing because there is no heat involved in the printing process warping and shrinkage rarely occur.
Most dimensional accuracy issues relate to features and thin walls that are printed below printer specifications. Material jetting prints support as a solid structure from a soft secondary material that is removed after printing. The solid nature of the support results in surfaces in contact with the support being printed to a high level of accuracy. Care must be taken when handling parts produced via material jetting as they can warp and dimensionally change as a result of exposure to ambient heat, humidity, or sunlight.
Fused deposition modeling (FDM) is best suited for low-cost prototyping, where form and fit are more important than function. FDM produces parts one layer at a time by extruding a thermoplastic onto a build plate.
For large parts, this can lead to big variations in temperature across the build platform. As different areas of the part cool at different rates internal stress cause the print to move leading to warping or shrinkage. Solutions like printing rafts, heated beds and radii at sharp edges and corners can help to reduce this. Different materials are more prone to warping than others. For example, ABS is know to be more susceptible to warping than PLA.
Selective Laser Sintering (SLS) produces parts with high accuracy and can print designs with complex geometry. A laser selectively sinters powder one layer at a time to for a solid part.
To restrict the likelihood of parts warping or shrinking during printing, SLS printers use heated build chambers that heat up the powder to just below the sintering temperature. This does still however result in temperature gradients in large SLS parts where the bottom of the part has cooled while the recently printed top layers remains at an elevated temperature. To further mitigate the likelihood of warping occurring parts are left in the powder to cool slowly (often for 50% of the the total build time).
Metal printing (specifically DMLS and SLM) use a laser to selectively sinter or melt metal powder to produce metal parts. Much like SLS, metal printing produces parts one layer at a time in a controlled, heated environment on industrial-sized machines. This layer-by layer construction coupled with the very high temperatures involved in the process creates extreme thermal gradients, and the net effect is that stresses are built into the part.
As a result, metal printed parts are at a high risk of distorting or warping, meaning good design practice and part orientation are critical to achieving an accurate part. Unlike SLS, support structures are vital to minimise distortion of the part during production. Parts are also generally built up on a solid metal plate and need to be removed once the print process is complete. A sound understanding of the process is required along with solid and lattice support structures to keep the part securely attached to the print bed and stop it from detaching. Most parts are also stress relieved (via a heat treatment process) after they’re built and before removal from the build plate (doing so allows the crystalline structure to relax, preventing failure later).
The following HP Multi-Jet Part Design Guide has been assembled to help users of the MJF process for the manufacturing of their parts better understand how to go about designing parts to harness all the advantages while minimizing the limitations of the MJF process. For more information on the Hewlett-Packard (HP) MJF 3D Printing process check out our process page or our how it works page for this technology.
Before sending a job to a 3D printer, the model to be printed needs to be tessellated. That means that its geometry needs to be converted into triangles, which are used by the printer to create layers. It is very important to pay attention to this step: if not done correctly, it can cause problems such as inaccuracy or slow processing. Standard formats in the additive manufacturing industry include 3MF (with more information about the model) and STL. A normal file size for a model is about 1–30 MB, but the size depends on the type of software that created it, the number of triangles, the number and level of details, and so on. When exporting to STL in a CAD package, you are often required to introduce some parameters such as angle tolerance and deviation chord height. These parameters define the resolution and file size of the part. The following tips will help you to export with the best surface to file size ratio.
Too many triangles are difficult to process and, when a certain size is reached, the extra triangles do not provide any further accuracy. For this reason, an excess of triangles could increase processing time for no benefit. Triangulation of a surface causes faceting of the 3D model. When the parameters described in the last section are used to output an STL model these issues are eliminated. Also, specialized 3D printing software like Magics can be used to eliminate unneeded triangles from an STL file without effecting its accuracy or quality.
There are some specifications to bear in mind in order to avoid issues in parts, and to achieve the best quality. The minimum printable features in planes X, Y, and Z are as follows:
Multi Jet Fusion technology allows you to print letters and drawings with a very high resolution and definition. For the best possible output, any text, number, or drawing included in a part is recommended to have at least .05″ [1.27mm] of depth or height. The best orientation for embossing letters is to place them upside down in the build chamber, while for debossing letters it is better to place them face up to achieve the best resolution.
The general rule of thumb for the MJF process is +/- .0075″ [0.2mm] up to 3.93″ (100mm) and +/- 0.2% above that value. For a much more detailed breakdown of 3D printed part accuracy beyond what is detailed in this HP Multi-Jet Part Design Guide please see our page dedicated to this topic.
We have included 3 of the most popular examples / options of the internal structures that can be used with MJF parts in this HP Multi-Jet Part Design Guide:
Multi Jet Fusion allows you to print topology-optimized, generative designs or even small lattice structures. This kind of design helps to reduce the weight of the part and the quantity of material used, which not only reduces the cost of the part but also helps to reduce the operating cost in applications that are very weight-sensitive.
Parts can be printed hollow, this greatly recuses the amount of heat that builds up in the part during the printing process allowing for more accurate parts and also allows them to be lower cost (less raw nylon and fusing agent are used). One down side to consider is that due to the parts being hollow they can be a bit weaker. If the parts printed are hollow, drain holes can to be added to the design to remove the unsintered material. The minimum recommended diameter of these drain holes is .25″ [6.35mm] and a minimum of 2 of them is recommended to allow for compressed air depowdering. We can also leave powder trapped in the parts, this helps save cost on complicated depowdering / plugging of parts but if the part needs to be dyed black this is not recommended as it causes the parts to float. At F3DP we utilize a specialized software called Magics that allows us to very easily and quickly hollow and add drain holes to parts as needed. We offer this for free to our customers and can work with you to make sure you original design intent is maintained.
This option is a combination of the benefits found in hollowing a part combined with the benefits of a latus structure. It keeps the part very strong but cuts out a large volume of material saving on both cost and loss of accuracy due to high heat during the build. The only concession that needs to be made to a parts design is that one end of the honeycombed region needs to be left open so the cells can be depowdered. If this is not a option please consult with F3DP directly on your part as there may be other alternative designs we can propose to you. At F3DP we utilize a specialized software called Magics that allows us to very easily and quickly honeycomb parts as needed. We offer this for free to our customers and can work with you to make sure you original design intent is maintained. The following table will give you basic dimensions that should be used for designing honeycomb features should you choose to design them yourself:
Sometimes a pair of printed parts need to fit together for the final application. In these cases, you are recommended to have gaps of at least .015″ [0.4mm] (±.008″ [0.2 mm] of tolerance of each part) between the interface areas that should fit together, in order to ensure correct assembly.
Assembly parts that are printed together should have a minimum clearance of 0.7 mm. Parts with very thick walls above 50 mm should have a higher gap in order to ensure proper performance.
Parts larger than the maximum build size can be printed with Multi Jet Fusion by splitting them into different parts. They can then be joined together by gluing, welding, or by pin inserts. If you plan to glue parts together, you are recommended to include interlocking features such as those shown in the pictures below: as a guide to position the parts, to help them to bond together, and to facilitate the gluing process. Remember to leave an additional space of .004″ [0.1mm] – .008″ [0.2mm] between parts for the glue, in addition to the minimum spacing between parts printed as assemblies (see above). At F3DP we utilize a specialized software called Magics that allows us to very easily and quickly split parts to make glue joints as needed. We offer this for free to our customers and can work with you to make sure you original design intent is maintained.
We recommend using Bob Smith Industries Maxi-Cure™ / Insta-Set™ glue for assembling HP MJF parts.
A customer requested to know how well our standard glue joint would hold up to repeated shock loads. We devised this simple test to prove out the strength of a HP MJF glue joint as well as do a metal vs Nylon wear test at the same time. Here are the results of that testing we are including in this HP Multi-Jet Part Design Guide:
One of the most useful abilities of the HP MJF technology is its ability to print threads directly into a part. This saves the need to use a insert like a Helicoil or heat set insert. It also eliminates the need for doing secondary tapping operations after the part is printed. In our experience with production parts the use of a printed in thread can save days worth of extra shop time spent tapping holes.
When designing long (over 6″ [152mm]) and twisting (more than one 90 deg turn) passages for things like compressed air or vacuum it is recommended to keep the minimum diameter of the passage to .1875″ if at all possible. To remove material from narrow ducts, consider designing and printing a strip or a chain through the duct. When the parts have been printed, you can pull out the chain to dislodge most of the material. Any remaining material can be removed by the normal cleaning process. If duct work is small in diameter or complex in routing its recommended to consult with F3DP on its design to incorporate more advanced best practices in to the design.
Multi Jet Fusion parts are made of thermoplastic materials and can be re-melted and re-formed once printed. Heat-staking and ultrasonic installed inserts are recommended for thermoplastic materials; however, pressin, self-threading and expansion inserts may also be used in some applications. The following information is being provided in this HP Multi-Jet Part Design Guide to help you with selecting the proper insert for your application:
The hole diameter is very important to achieve the desired strength, oversized holes will result in a reduction of the joint strength and undersized holes can potentially crack the part. Multi Jet Fusion parts have a tolerance of +/- .0075″ [0.2mm] in small features and this is usually above the supplier specifications. For this reason, it is important to select a type of insert that is compliant with hole deviations and a lower performance should also be expected.
Traditionally a boss diameter is two times the external diameter of the insert for inserts under .23″ [6 mm], a .11″ [3 mm] wall thickness applies for all larger inserts. Exceptions include applications incorporating supported bosses, reinforced materials, and heat installation. Special consideration should be given to cold press installations where stress will be increased and may require larger boss diameters.
It is important that the insert bears the load, and not the plastic, to avoid jacking the insert out. The mating component hole should be smaller than the face of the insert but still allow the connecting threaded fastener sufficient space to function normally. The mating component must also withstand the stress generated by the clamping force. In instances where the mating component will also be plastic, the use of a secondary insert or collar should be considered to avoid creep.
The recommended insert for Multi Jet Fusion parts depends on the type of installation and the geometry of the insert. This is a summary of the main types of insert available for plastic parts:
Snap fits provide simple and economical way to assemble parts, often saving time in assembly. This is possible with a protruding feature on one part, which flexes during assembly into a groove or slot in the mating part. When fully seated the protruding feature returns to its initial position.
The cantilever snap-fit is the most commonly used type of snap-fit. It consists of a cantilever beam with an overhang at the end. In this type of snap-fit there is a direct relationship between the robustness of the assembly and the strength of the snap-fit.
When it is not possible to design a cantilever snap-fit without compromising the robustness of the assembly and the strength of the snap-fit due to material or geometrical constraints, an L-shaped snap-fit can be an alternative. Adding a groove to the base
of the snap-fit increases its flexibility while reducing the strain on the beam, compared with a cantilever snap-fit.
The U-shaped snap-fit is another alternative to the cantilever snap-fit when it is necessary to increase the snap-fit flexibility within a reduced space. This U-shaped alternative is extremely flexible, and thus easier to remove. This type of snap-fit is usually used in cases where the parts need to be pulled apart repeatedly or when two parts don’t require a lot of force to stay in position (e.g., in a battery compartment lid).
The annular snap-fit is an assembly method usually used between two cylindrical or ring-shaped parts or between two rotationally symmetric parts, where the deformation required to assemble or disassemble the snap-fit is made in a 360º direction at the same time.
With this assembly method, one part is designed with an undercut and the other is designed with a mating lip. The joint occurs through the interference between both parts during the assembly operation.
The torsional snap-fit is an assembly method where the flexible point is in a torsional bar instead of the self–snap-fit body. When the torsional bar is pushed down, it turns slightly and opens the joint.
The minimum recommended thickness at the base of the cantilever is 1mm (0.04in).
The minimum overhang depth (t) should be at least 1mm (0.04in)
It is recommended to add a radius at the base of the cantilever to avoid sharp corners and reduce the stress concentration. This radius should be at least half of the thickness (h) of the base of the cantilever.
It is recommended to avoid sharp edges at the end of the snap-fit overhang, adding a small chamfer to prevent breaking during the assembly operation.
As mentioned previously, the snap-fit overhang usually has a gentle chamfer to facilitate the assembly operation. The inclination of this chamfer angle (α) directly affects the mating force (P). If the angle (α) is reduced, the mating force (P) will also reduce. The
recommended assembly angle value should be between 35º and 40º.
The way the overhang is designed determines whether the snap-fit can be disassembled and reassembled several times. The disassembly angle (β) affects the ease of joint disassembly. For example, a 90º angle (β) can never be disassembled. However,
a snap-fit with a disassembly angle (β) equal to the assembly angle (α) will need the same mating force (P) for both operations.
When designing a snap-fit, there must be a gap between the protruding feature and the groove to ensure a proper performance, even including the worst tolerance case as shown in the following figure:
These guidelines are to be used as a starting point in understanding the basic aspects of part design and preparation for FDM components. When designing a part to be built using FDM technology, build process must be considered. FDM is accomplished by extruding thin layers of molten thermoplastic layer by layer until a part is produced, because FDM produces parts with specific characteristics and capabilities different from those of other prototyping processes, the systems have become increasingly used as a tool for producing manufactured products. This FDM Part Design Guide will be a valuable resource for evaluating and adjusting your designs to get this best results possible from this 3D Printing Technology.
The following information builds from conventional plastic part design to explain design considerations for manufacturing high-quality FUSED DEPOSITION MODELING (FDM) parts.
Forerunner 3DP automatically adds shrink rates to the part when processed, so shrink factors do not have to be designed in. Default values can also be adjusted to fit specific geometries when large production runs of similar part designs are needed.
Since FDM systems add small amounts of molten material in a heated environment, warp is not a common problem. However, to avoid potential warping (deformation of vertical walls) when building thin-walled sections of a model, designers might select to add ribs to the walls (similar to what would be done with standard injection molding processes).
Holes (those in bosses as well) on an FDM part are generally fractionally undersized. When tight tolerances are required, holes will be drilled or reamed to ensure the diameter is accurate.
Minimum pin or column size is a function of part orientation, tip size, and length. A Forerunner 3DP Sales Engineer can expand a column or pin to a minimum size based on the selected slice thickness. Custom groups can also be used to create smaller features down to 0.019 in. (0.48 mm).
Minimum wall thickness for FDM parts varies depending upon the slice thickness that will be used to build the part.
These wall thickness figures are a single contour width. Note: building multiple layers while using the minimum contour width will cause the feature to be brittle. (Note that warping may occur if there are large extents of minimum–thickness, vertical walls without support features like ribs or a support material tower.)
Forerunner 3DP encourages the use of the recommended minimum wall thickness (below), which will eliminate brittleness.
When designing built-in threads, avoid sharp edges and include a radius on the root. Sharp edges can be stress concentrators in plastic parts. Creating an ACME thread design with rounded roots and crests has been found to work well when using FDM. Also, use a “dog point” head of at least 1/32 in. (0.8 mm). This dog point design makes starting the thread much easier. Small threads produced from the FDM process are not recommended and not possible for holes or posts smaller than a 1/2″ diameter. An easy alternative is to use a tap or die to thread holes or posts.
Because FDM is an additive process, undercuts for design features such as O-ring grooves are easily handled without causing manufacturing issues.
Although fillets are not necessary in FDM parts, they can be used to reduce stress concentrations and increase the overall strength of the part. Design fillets with an outer radius equal to the inner radius plus the wall thickness to maintain consistent thickness.
Draft is unnecessary in FDM parts.
Forerunner 3DP can make single FDM parts as large as 36 in. x 24 in. x 36 in. (X, Y, and Z) (914 mm x 610 mm x 914 mm). Designers should note that extruded plastic has its strongest strength in the tensile mode along the x-y plane. Since the layers are held together by “hot flow” across the strands (one strand is cooling while the other is laid upon it), the lowest strength is in the Z-direction for both tensile and shear modes.
The Z-dimension brings another consideration to the FDM process. Overhanging non-supported features, such as the top of a closed box, require a foundation of support material to be built, which increases build time and material usage. Because of this, build orientation is usually determined by the part processor. For example, half of a box-shaped casing will be built with the main exterior facing down, so that no internal support is needed.
Proper clearance should be given between mating assembly parts to prevent them from fusing together. The standard guideline for creating clearances on assemblies being produced fully assembled is a minimum Z clearance of the slice thickness. The X/Y clearance is at least the default extrusion width based on a suggested minimum wall thickness. The minimum clearance needed for mating parts, when not producing the components fully assembled, is equal to the tolerance of the FDM machine itself.
Parts may be sectioned (prior to manufacturing) in CAD, commercial rapid prototyping software applications, or by the Forerunner 3DP team. Sectioning can be used to:
Living hinges made from FDM materials can be used for a small number of cycles. If additional cycles are required consider using a different hinge design.
When using fastening hardware, Forerunner 3DP suggests designers use a cap screw or a flanged cap screw. The flat surface eliminates multidirectional stresses from cracking the part. Washers can also be used to spread the load over the largest possible surface area. Lock nuts, embedded nuts, or metal inserts are all stronger fastening options than adding threads to the FDM plastic.
Many times the design of FDM parts can be solid rather than using a hollowed out design supported by bosses and ribs. This can reduce build time and use less support material. It is not necessary to reduce wall thickness of a boss, rib, or gusset in FDM parts. Generally bosses can be the same size as the part thickness or up to 0.02 in. (0.5 mm) less. It is also important to use gussets or ribs to support the bosses in FDM parts. This will increase the amount of stress the feature can withstand.
Minimum suggested text size on the top or bottom build plane of a FUSED DEPOSITION MODELING (FDM) model is 16 point boldface. Minimum suggested text size on vertical walls is 10 point bold. In most cases the supports generated to support text on a vertical wall can be eliminated to save time and material.
Since the FUSED DEPOSITION MODELING (FDM) process uses engineering-grade thermoplastics, the parts produced are capable of withstanding a number of post-manufacturing processes, including machining operations such as drilling and tapping, sawing, turning, and milling. (Note that heat is easily built up in plastic parts, so removing the material slowly and using coolant keeps the part from distorting.) Other post processing operations may include smoothing, burnishing, sealing, joining, bonding, and plating.
Stereolithography (SLA) allows you to design complex models and patterns and have them manufactured in record time. The high level of accuracy makes SLA ideal for manufacturing concept models, form and fit studies, precision patterns, and high quality appearance models, etc. This SLA Part Design Guide can be used to optimize your design for the SLA 3D Printing process.
Max build envelope capacity: 20” x 20″ x 20″
NOTE: Parts much larger than the machines build volume are possible, the CAD data is split into sections, printed, then assembled by a model maker using light welding. The finished part is just as strong and functional as if it had been printed as a single piece.
• Tight tolerances
• Extensive material options
• Smooth surface finish
• Machinable and paintable
• Large parts
• Optical clarity
It is highly recommended that you review your STL file prior to quoting and/or manufacturing. If the resolution is too low, you can get faceting on curves which will result in poor feature definition on parts.
The resolution of the SLA process limits hole sizes to .025” or greater. Smaller holes typically will not be created.
If a part has internal threads, it is recommended that helicoils be used instead of printed threads. Printed threads suffer from resolution tolerances and are fragile, resulting in a low or non-existent pull out strength.
We recommend Helicoils for SLA parts from McMaster-Carr
It is recommended to core solid parts whenever possible in order to reduce build time and material consumption. This will result in a lower cost to manufacture parts.
Inaccessible areas on parts cannot be properly finished. If it is required that these surfaces be finished, it is recommended to design the part in two pieces and assemble after finishing.
As a service to our customers F3DP is happy to split up your part design in our specialized Magics software to fix an inaccessibility issue.
It is recommended to design at least a .010” gap overall between any two mating faces in mating parts or assemblies.
When designing two parts that thread together, it is recommended to add a .020” mating allowance on large threads only (No. 1/2-20 or larger thread sizes) to allow the threads to function correctly. See the note also on Internal Threads in this document.
Recessed and embossed lettering on a flat surface should be a minimum of .020” deep (or high) in order to be clearly visible. Recessed lettering on a curved surface should be a minimum of .020” deep in order to be clearly visible. Lettering should be at least .010” wide.
Traditional knife edges are difficult to manufacture using the SLA process when they are located on the bottom surface of the part relative to the build platform. This is due to the diameter of the laser beam and the minimum feature size (build layer thickness). Knowing if a knife edge will build can be tricky for a non 3DP process expert, therefore, if you need a knife edge on your part bring it to the attention of the F3DP sales engineer who is processing your order and they will determine how to best orient your part to preserve the knife edge.
We recommend using tape to mimic a living hinge on SLA components this is due to the fact that parts printed with a living hinge will work for only a few cycles before they break.
While this SLA Part Design Guide might not have all the answers for your SLA part design, its a solid starting point. F3DP’s Sales Engineers are always happy to educate customers on the process and how to design successful parts for printing with it.
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