How It Works: HP Multi Jet Fusion 3D Printing

Hello everyone. My name is Paul DeWys. I am a sales engineer here at Forerunner 3D Printing and today I’m going to be giving you a little bit of a walkthrough of how we set up a build, and then run a build and then unpack a build on our Multi-Jet Fusion machine.

This is actually an HP Multi-Jet Fusion 4200, is the full name of this piece of equipment. So yeah, let’s kind of get into it.

This is Magics. This is a piece of software specifically written for doing build layouts for all kinds of different additive machines.

Today I have HP Platform pulled up on here. So, roughly 15 inches wide, 15 inches tall and about 11, 11 and a quarter inches deep, something like that.

So we’re going to populate our build with a bunch of parts, so we’ll start out by importing our parts here. And I already have them bundled into a platform.

All right, so it pulls in all of our parts. They’re all over top of each other. Turn off bounding boxes so you can see a little bit easier. So we need to spread all these out and start orienting them for the build. We’ll just do a quick auto placement get everything spread out. Now we can kind of see what we’re looking at here.

So with MJF specifically, we always try to point critical holes down. So you can see we’ve got some parts here that actually have another part nested inside them, so they’re a printed assembly. And with something like that, we want to … so this is actually I know going to have bearings pushed into it. So we want to orient those round features vertically in the build chamber.

So we’re going to start out with just picking, control picking a couple parts here and gong and telling it to indicate the bottom plane. Apply. Rotates all those parts, kind of throws them over top of each other, but we’ll fix that in a minute.

We’ve got two nesting details right here. Again, I know that those holes that are going through those parts, those are critical holes. This one’s super critical. It has actual dowel holes in it. We want to try and get those as accurate as possible. So, same thing, we want to orient those like so.

We’ve got some parts in here that kind of don’t matter as much about orientation. This one here is a cover that’s going to go over a flame cut steel detail to hook onto something. So just kind of looking at the build, looking at how thin all these features are and knowing what forces are going to be involved.

I’m actually going to lay this one down on its side so that the layers run in this direction. I think it’s going to make for a stronger part when we’re all said and done. So grab that, flip that guy over. This part right here I’m actually going to leave. That’s actually the orientation I want. It is another printed assembly. Now, these holes obviously aren’t running vertically like I’d prefer, but you can’t always get that. Sometimes you’re just going to have to deal. So yeah, we’ll have to maybe chase those out with a drill bit if they come out a little out of round or something like that.

This part right here really … I like the way that it kind of came in. I don’t think I’m going to touch that one at all. We’re going to leave that one be. And then this part here, there’s another one under there, again, I like how those came in. I thin that’s going to work just fine, so leave that alone. And then we have this camera lens right here.

Again, this is a print as assembly. I’ll translate it here a second so you guys can see it. So, you can see this is an assembly. We’ve got some living hinges, or I’m sorry, living springs built right into the part. So again, I think I want this face laying down, just kind of looking at the features and everything here, I think having that face up is probably the best bet for the best … you know, have those layers go through those springs so that the layer’s continuous through the spring. I think that’ll give us a better result.

Okay, so now our parts are all kind of mishmashed together. So I want to nest everything. So what we’re going to do … before we used auto placement, which is 2D nester … yeah, you can see it’s yelling about stuff maybe falling outside. So we’ll say yeah, place it outside if you can’t figure out how to nest it.

So it’s a 2D nester. So you can see we ran out of room on our platform to get all of our parts nested in there. But that’s why the beauty of using a MJF machine is you can nest in the Z as well. So we have an added plugin for Magics, 3D nester. This thing is really cool. It’s also really expensive. So it does not come with your stock install of Magics. It’s an added plugin.

So we’ve got all kinds of different options here. Part interval. Five millimeters, five millimeters from in from the sides. I’m going to leave all that alone. Manually end the nesting process. I’m going to leave that as well. I’m going to go down to advanced and then go to part settings. And a lot of times we use fixed bottom plane. So that means it’s not going to tip the part off of that bottom plane. It’s going to keep that fixed.

It will go up in the Z. I also like to say rotation angle, 90. This would mean it would only go 90, 90 when it’s trying to fit stuff together. I actually like to try to crank that down to 15 a lot of times if a parts will allow for it because it just gives you that much better chance of puzzle fitting everything together. And the name of the game with MJF, just like a lot of 3D printing technologies, you want to keep your Z height as low as possible, because Z height drives cost.

So we’re going to hit run and it’s going to start nesting. Okay. So this is a pretty small build platform so it went pretty frickin’ fast.

Yeah, everything looks pretty good. We’ve got a nesting density of 7.76 and nesting height of 99. And if you look, you can see I have an item on there. That’s my tallest item on the build and the floating stuff in the Z is nested at or right below that which is good so I don’t have anything driving Z height, which again drives time, which again drives cost.

All my parts that need to be oriented with holes in the vertical, or Z axis, everything looks good there, so I think we are ready to take and get this into the HP software and get it sent over to the machine.

So there is a plugin for Magics that allows you to send jobs directly to the HP machine. We actually just got the software a little earlier this week and we haven’t worked the bugs out yet. So we have kind of a bit of a ham-fisted way we have to do it right now. I’m going to show it to you guys. And just know that there’s a slicker way to do this out of Magics and this is just how we have to do it for the time being.

So I’m going to select all my parts. I’m going to go File, Save As, Save Selected Parts As. Then I’m going to go to where we’re doing our builds, we’re keeping our builds, Build Platform Data.

And I’m going to say Apply to All and I’m going to hit Save and it’s going through and grinding out all of those STLs. We can see DropBox is updating here. There’s all of my STLs.

So let’s hop over into Smart Stream 3D Build Manager. So this is the software that comes with the HP printer. It allows you to pretty much do what Magics does, but it’s very lacking in functionality. It doesn’t have any great nesting features or anything like that. Not a lot of great repairs tools. It’s just kind of bare bones to be honest with you.

We’re big fans of Magics here, so we’re only using this because we don’t have that one plugin working yet. As soon as that’s working, we’ll probably never touch this again.

I’m going to add some parts. Make sure I’m in the right folder. I am. Circle all those, open. Again, for some reason it drops everything a little bit below where it needs to be, so the yellow items are all flagged. Pretty simple fix though, which is to turn that on, grab this arrow, and just start … there we go. Drag it up and it kind of snaps to the bottom of the machine for you. So now everything is blue. Everything looks good. So we are ready to send this out to the printer. We pretty much leave these alone. We always, 99 percent of the time, run balanced profiles.

So let’s hit Send to Printer. Yeah it’s fine. We already did that in Magics. Continue. So it’s slicing. And sending. There we go. Job report successfully generated.

Here’s our job report that we can print out and it goes with the parts so we know what’s what, quantities, everything like that.

So we’re done. So now I’m going to flip over to a POV camera and I’m going to go wander around the lab a little bit and we’ll get this build running.

All right, well welcome to our MJF Lab. So these are the two pieces of equipment that make up kind of an MJF 3D printing system, if you will. You have the printer, which obviously does the 3D printing work, and then you have a processing station, which is essentially where you unpack builds and then reload the cart with material and get the build cart ready to go into the printer.

So essentially the most expensive vacuum cleaner you’ve ever seen would be the best way to describe it. So I’m just going to start walking you guys through what goes into getting that machine up and running over there. So it starts with unpacking the last build. All right, so we have a build that was run yesterday and then put in the system for cooling, and as we can see, fast cooling is finished. So just to help you understand this a little bit, so this right here is a build bucket, build cart, build station. What do they actually call it?

An HP Jet fusion 3D Build Unit. There you go, that’s what you actually call it. I can never remember that much so we call it a bucket. So you’ve got one there and then we’re going to be putting it in there once we’ve unloaded it and got it reloaded with more powder for the build we just set up. So we’ll start with kind of walking through a couple things here. So when these parts print, it’s centering the nylon, which means melting it together, and so that means that this build bucket gets really, really hot.

The powder inside of it gets obviously right up to the centering temperature or the melting temperature of nylon so you can imagine after you finish a build of, you know, a couple inches or even the full 15 inches, there’s just a lot of heat into this powdered mass. So we have to cool it, and we can’t just quench it. We can’t just pull it out and just start digging in there even if we could find a way to keep ourselves from getting burned because it might cause part quality issues.

Maybe parts are warped or things like that because they cool too fast, so I mean, it can take, you know, it can take 15 to potentially up to 20 hours to fully cure and cool one of these buckets to the point where you can get in there and start breaking your parts out and everything like that. So you know, the machine itself can kind of print at almost an inch an hour, you know, a little less, a little more depending on settings and things like that, but then you’ve got to cool it.

And they call it fast cooling but it still takes quite a bit of time, so what I’m going to do is I’m going to show you guys a time lapse of me breaking this build out and getting all the parts pulled out and getting it ready to be refilled with more powder. Okay, and there you have it. We have unpacked the previous build, cleaned up the build bucket there, and then repacked it with more powder so we are ready to pull that bad boy out and get it stuck in the machine.

All right, so you pretty much just come over here and eject and it does its disconnecting routine. You can hear it unlock and now you just give her the old heave ho. And there we have it, ready to go. So next up we’ll be starting our build.

All right, so before we get our build going, I’m gonna take little bit of time to kinda walk you guys through how this machine works. I’m gonna preface this by saying, at the end of the day, I’m really just the sales guy; our machine operator knows this thing inside and out, so I’m gonna probably gonna end up giving you a little bit of potential bro science here, cos I’m not sure I have all my exact facts and figures, but I’m gonna at least give you a basic walk through of the machine and hopefully I can get everything right here, so please don’t crucify me in the comments.

All right, so we have our printer and it’s made up of three basic elements here. So we have this array of lights here in the cover as well as a thermal camera. Essentially, that heats the build chamber and specifically heats each layer of nylon as it’s laid down to maintain the correct temperature which is basically a little bit below where the nylons starts to melt. Because you wanna get that nylon really, really hot so when you put the fusing agent on it, and then hit it with some other lights that we’ll talk about in a minute, it cures and snaps and melts and binds together and essentially fuses that layer and it fuses to the layer below it. So essentially heater, that’s the best way to think about this.

Then in the back, we have a roller. This essentially picks up fresh material from either side of the build platform and these pockets right here. So these flippers come up and there’s just a mound of powder right here and that roller moves across and it spreads a fresh layer, three thousandths thick of nylon onto this build platform.

Now obviously as we build, this platform drops. So every time we spread a layer, fuse it, this platform drops three thousandths. Spread a layer, fuse it, drops three thousandths. So, this guy here just moves back and forth and spreads the material. Tuck him back there. All right, I’m gonna pull the actual print head and light out so we can look underneath a bit. So we’ll do that right now.

All right, so this is the printing head and the fusing head. This is where the magic really happens with the MJF process. So let’s actually pop this door open here a second, and go underneath and take a look.

So normally, our build bucket goes under this area right here. Right now it’s pulled out, and if we get underneath here, hey, look at that. So we got two big lights under here and then you also have a bunch of print heads in these three clusters right there. So essentially, as this thing rolls across the fresh three thou layer of nylon, it’s squirting out a bunch of fusing agent which is actually what locks the nylon together when it gets hit with those bright lights and fuses it together, and detailing agent which we put around the outside. And the detailing agent does exactly what you think it does, it helps make sharp corners, round holes, it really keeps a lot of resolution in the parts. So there’s two additional consumables beyond just nylon powder; there’s a fusing agent and the detailing agent. But when this is all done, you’re just left with sintered nylon.

The fusing agent actually is what gives the parts their black base color too. So, this guy moves over here, moves over there, back and forth, and back and forth, as the build progresses. You also have literally a big old roll of paper towel down here and every time the build head finishes and moves back over here, this rubber squeegee pops up and presses this paper onto the bottom of the build unit and wipes it essentially. I believe that’s so you don’t get build ups on the underside of fusing and detailing agent on all those nozzles which I think would cause build issues.

So I think that’s everything, that’s kind of basic operations of how an MJF machine functions at a very, very, very basic level. So yeah, lets get this build cart loaded in and get it going.

Okay, so now we’re going to insert the build bucket into the machine, this is gonna be a little bit tricky one handed, but we’re gonna give it a shot. All right so now we’re gonna give her the heave how, you actually see it rise up once we get it in there. There we go. Locked and loaded, ready to print.

All right, so shut this door, and close the top and you can hear, we’re getting close to launch. Okay, so we are ready to start the build. So we’ve already sent the build over to the printer via the software on my computer back in the office, so you can see there is our build and we can kinda take a look make sure it’s sorta what we expected to see, yeah that looks about right. Okay so now we just have to print magic button here.

Oh, rookie mistake. We have to arm the printer. All right, so the printer’s armed and initializing and once this is done, the print will begin.

Okay, so the next step for these parts that we just pulled out of the build bucket from yesterday, they still have powder caked on them. You can see the holes are still filled with powder so we give them a light bead blast. After that, they’re pretty much done unless we’re going to color them. We do dye parts black. We also leave them raw. Raw is the cheaper option. These parts are going inside an enclosure. No one’s ever going to see them so the customer said, “Just leave them raw,” but I will show you guys some black parts, too.

When it’s all said and done, you wind up with a part that looks a little something like this. We hit them with an air compressor just to blow off all the little residual dust, and we’re all done, but basically that’s what it takes to finish a MJF part after it comes out of the build bucket. All right, so I’m going to show you guys how we actually go about dying these parts after they’re printed. For example, when the part comes out of the machine, it’s got this nice, kind of gray, almost-ash look to it. A lot of our customers want black parts. Now, believe it or not, this part is actually black. If you were to go after this thing with an end mill or a lot of sand paper, something like that, you would eventually get down to a nice, black part. But because there’s powder that’s just a micro layer baked onto the outside of this, it’s got this kind of ash-gray appearance to it.

What we do, believe it or not, is literally take a Crock Pot, fill it with black dye, turn the heat on, and make ourselves a MJF stew. This is how we do it. Here you can see we’ve got some end-of-arm gripper fingers that we’re working on, and we’re just dying the parts black. Now, the cool thing about this is, let’s say you scratch one of these parts. Well, the dye soaks into the outer layers of the part, but the inside of the part is actually already black. You can’t really scratch these. I mean, you can, but they won’t … It’s not like paint where you’d scratch the paint off. Yeah, so that is how we get black parts when we’re doing MJF 3D printing.