How to use GrabCAD Print for SAF/H350 Printers
With a new printing technology (SAF powder-bed) comes new ways of using slicing software. This tutorial covers how to access the new printers in GrabCAD Print, how to get a license, and how to set up 3D nests of hundreds of powder-bed parts!
Also covered are some Design For Additive Manufacture (DFAM) tips on this new type of Stratasys printer!
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Step 1: A new technology added to GrabCAD Print!
It’s not very often we get to celebrate a new major addition to the Stratasys Software family, so I’m very pleased to announce that, as of GrabCAD Print version 1.66, we are officially supporting a BRAND NEW type of printing technology, Selective Absorption Fusion (SAF)!
Here’s the change visually:
In other words, this is opens up a whole new CLASS of parts you can now make through GrabCAD Print:
To learn more about the details of SAF printing itself, go here: https://www.stratasys.com/en/3d-printers/printer-catalog/saf/h350/
But the main difference for us software folks is that, being a powder-bed process, SAF allows for 3D stacking in a nest, which is pretty different from how we’ve been using GrabCAD Print in the past. There will be automatic 3D stacking and nesting, and manual as well.
So let’s see how to take best advantage of this new technology.
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Step 2: Get a license if you want to print
Starting with version 1.66, all users of GrabCAD Print will be able to SEE the new H350 SAF printer in their printer template list. All you have to do is search for ‘H350’ and choose the template on the right hand menu:
All GrabCAD Print users will be able to see a SAF template printer, and add parts to the 3D nest (we’ll talk about how later), but you won’t be able to save your work. Only paid license users will be able to choose actual printers, save .print files for SAF or send a nest to a real SAF printer:
Yes, that’s right, this is our first PAID printer license in GrabCAD Print, so if you want to connect to and send files to your new SAF printer, contact your local reseller for a paid or trial license. Licenses will be handled by your email and GrabCAD Print account (in the lower left-hand corner of your screen), so contact print@grabcad.com if you ever think you've bought a paid SAF license but don’t see it.
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Step 3: Let's use the software! (The BIG section)
The first thing you’ll notice when opening a SAF printer in GrabCAD Print is there are now TWO places to rest your CAD files, an infinite 2D Preparation Tray, and the actual 3D Nest:
The idea is that you start by adding models in the 2D area, duplicate as many copies as you need, then send models to the 3D area to finish setting up the tray. (There is no way to lay out multiple 3D Nests at once in GrabCAD Print yet. You should ‘Save As’ your work as different .print projects to work around that.)
And did you notice those little numbers in the corner?
That’s a live count of how many separate CAD files are in each area, so you don’t have to keep switching back and forth. Obviously, by the end of your nesting, you want the count in the Preparation Area = 0. (If you don’t see that, you’ve left some orphaned files behind!)
I use those little numbers all the time, they’re great.
(And in the words of a great dwarf: "Assemblies still only count as ONE!")
Adding files is the same as with any other GrabCAD Print tray (‘Add Models’ button or drag in), you can add STLs or native CAD files, I’ve got the STL I want to print below and a VERY useful CAD part added to my 2D Prep Area:
You can see from my CAD ruler (always in the right units, unlike STLs), that each gray square in the prep area is about 10 cm or 4 inches wide, which is VERY useful when you are trying to eyeball the size of your part on an infinite plane that extends in all directions with no landmarks.
(If you don’t have a similar ruler made for your 3D printing toolbelt, email me at shuvom@grabcad.com and I’ll send you mine. I use it a TON.)
Now that we’ve got files on the tray, this is the general sequence you want to work:
The main point is, Duplicate your needed number of copies AFTER doing all the other steps, because it’s much faster and easier to check or fix the rotation of one file than a hundred.
Let’s see how this works for the electronics clip we’re printing. The files are already on the screen, so let’s check them:
Check is in a similar location to the ‘Slice’ button on FDM GrabCAD Print screens, and after hitting ‘Check All Models’:
This is checking for general water-tightness, open surfaces and the like. It’s NOT performing a minimum thickness check or other DFAM type checks (if the part is too thick for SAF and might retain too much heat, for example).
But all parts need to be checked before sending them to the 3D nest. Half the time, if my “Start Nesting” button is grayed out, it’s because I added a new model to the prep area and didn’t check it. (Or if you checked the models, closed GrabCAD Print, and re-opened the project.)
It’s going to happen to you too, mark my words. In fact, it's probably going to happen so often, I channeled my inner Boomer and made a meme for you to remember this moment by, BEFORE you call our help line asking why you can't send files to your nest:
If you run into this problem in the future (like I have many times), remember the penguin.
Now, it’s time to fix rotation. This is not a required step, you can leave the 3D auto-nester free to rotate your part in any way it wants, but orientation affects the mechanical and surface properties of SAF parts. If you want 100 parts to have consistent properties in a SAF build, force all their orientations to be the same.
On our part, we care most about the ‘Stratasys’ lettering:
Think of injection molding: in every molded part, there is an ‘A side’ that you care about, and a ‘B side’ where you put the injection marks, ejector pins, blemishes, etc., since the customer won’t see them. In the outer housing of a vacuum cleaner for example, the A side is the pretty outside that the customer would see, the B side would face the motors and belts and stuff.
For SAF printing, you usually want your A side to point DOWN.
(We’ll talk about one exception later.)
So I’m going to use the Orient tool (same location as regular GrabCAD Print) to flip the lettering face down, and ‘LOCK’ the X and Y rotations, letting the part spin around Z like a top later on:
As long as that big flat face is pointing down, that will give us the flattest smoothest properties for that surface, consistent across how ever many we’re going to print. Rotating like a top in Z won’t alter material properties. (We’ll talk more about this in the DFAM section at the very end.)
Now that our rotation is fixed, let’s Duplicate the model.
For SAF prints, you can either:
· Duplicate fewer than you need and keep adding in batches until the nest is full,
Or
· Duplicate a ton MORE than you need, use the auto-nester as a blunt hammer, and then delete the extra orphaned copies from the prep area at the end.
There is currently no “Duplicate exactly as many copies as will fit in my 3D nest” command in GrabCAD Print.
So let’s have some overkill and duplicate 200 of these clips:
Make sure to do the math right:
And then:
The Duplicator tends to lay out your models in a very pleasing radial pattern, I’ve found.
But look at how all the copied models ALSO have their rotation locked (black lock icon in the model tree). This is why we duplicate last, because I wouldn’t want to go through and set rotations for 199 extra models now, even if I can box-select them.
Now we’re ready to send things to the 3D nest!
What you’ll see is a screen where you can set the main auto-nesting parameters: spacing, target density and target time:
Setting the Minimum Spacing is largely dependent on HEAT. Thin parts more easily shed heat during a SAF build, thicker parts tend to retain heat and are more at risk of warping. You will want to space thicker parts further apart to allow the powder to remove heat from the faces. This will have to be learned by experience on your specific geometry, so keep records of the spacing used in each build in a way you can search 6 months later.
Stop Criteria is when your auto-nester will finish. 12% is a good density for SAF nests, and what I usually set for my stop criteria.
If I am doing a quick demo just trying to show off the software, I’ll set 00:03 minutes as a stop time just to make sure the nester doesn’t go on forever if it doesn’t hit 12%. If you are really trying to pack every last model into a production build, it’s okay to set the time higher, and let the nester go for 5, 10 minutes or more.
(If you do, make sure to save the .print file of the resulting nest, so you don’t have to spend 10 minutes nesting again if you need to repeat the build!)
After choosing all your settings, hit “Start Nesting” (if you can’t, remember the penguin!) and this is what the process looks like:
So let’s analyze the end result:
You can see I stopped the nesting before it reached 12% or even 3 minutes, just because I was watching the purple line on the graph (nesting density) and it had basically leveled off. Again, you can run your nesting algorithm as long as you like, but at a certain point the density will stop increasing, meaning you should stop there.
Our A face is still down, we got 113 out of 200 models into the nest, and the nest is Valid. So now we’re ready to hit ‘Print’!
That’s all you need to know to cover the basics of SAF printing in GrabCAD Print, but I’m going to cover one last aspect before going over the advanced SAF DFAM tips: Manual nesting.
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Step 4: A short sidebar about MANUAL NESTING
If you have certain XYZ coordinates you want to place certain parts in your nest, use Manual Nesting. This is most often done with dogbones and other calibration pieces you will space out across your nest, then test for material properties after the build, to make sure things were consistent across the entire 3D nest.
Typically, I would suggest using Manual nesting FIRST to place your dogbones in your corners, lock them in place, and then use Automatic nesting on the rest of your parts, to fill in around your dogbones.
It looks a little like this:
And then you can use the same steps from before to fill in the space IN BETWEEN your manually nested parts with the auto-nester (we call this 'hybrid nesting):
So with a combination of manual nesting for your measurement parts which always have to be in the same place every time, and automatic nesting for everything else (maybe with certain rotations fixed to give you the same material properties), you should be able to nest anything you need in GrabCAD Print.
(Side note: if you need custom sinterboxes, you will need to make those up in CAD and bring the whole thing in as an assembly for now, we hope to address that in the future.)
Now, let's go over some DFAM tips on HOW to use your new SAF printer, and we'll be done!
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Step 5: Tips on HOW to print in SAF
The biggest caveat for this section is that DFAM will always depend on:
- Geometry
- Effects you're trying to achieve
- Your printing schedule- if you want FULL trays or FAST trays
And a few other factors. What we're talking about here is GENERAL principles.
In general, the two factors you are most concerned about in SAF printing are SPACING and ORIENTATION.
Spacing we've already covered, saying 2 mm (0.079 in.) is a good starting point for thin parts, and 5 - 10 mm (0.19 - 0.39 in.) for thicker parts, but just like packing coals into one corner of a grill, if you stack a BUNCH of thick parts in one concentrated area, you may have to space even wider.
There's no thermal FEA being done on trays in GrabCAD Print, so a lot of knowing what spacing to use will come from experience. (Keep good visual records of how you nested, by saving .print files in an orderly system!)
And hollowing and latticing thick parts are also good ways to remove bulk from the model, and thus reduce the heat generated during printing. (If you do create a hollow part, remember that interior volumes will still fill up with unfused powder, so make sure to leave TWO holes to drain the powder out later- one for powder egress and one for air intake!)
There is no minimum self-supporting angle for powder-bed, and dry powder material removal is pretty easy, so lattices work much better here than in FDM, for example, and are a great way to remove bulk, which removes heat, which allows tighter spacing. If you ever need help latticing something, I've done previous tutorials on that before using Rhino, but am also CURRENTLY researching softwares like nTopology and 4D, so email me at shuvom@grabad.com if you want to learn what I've learned.
Orientation is something you have a lot more control over. In general, your downward facing surfaces are going to be smoother and flatter, so if you have a customer-facing 'A side' of your model, you'll want it to point down:
The main exception to this rule is if you have MULTIPLE customer-facing-faces (like four sides of a cube) and in that case, you want your multiple faces to all be VERTICAL- in that case they will not be as smooth as your downward face, but at least they will all be THE SAME:
Even slight changes in angle can affect surface finish.
Below is just a sample of the tests we did, if surface finish will be a make-or-break quality for you, you are invited to do the same test on parts of your own design:
You can see this particularly with TEXT labels on your part. In general, you want the text to be:
- Debossed INTO the model rather than embossed OUT of the model
- Large enough to not disappear due to the slicing process of the SAF printer (has to do with offsetting faces to allow for thermal expansion, just keep it over 14 point font and you should be okay)
- On the SIDE/VERTICAL faces of the model, rather than the top.
Here's a visual:
One hidden tool which can really help with text like above is the new Label feature in GrabCAD Print, which currently only works for SAF machines, but we hope to expand it soon:
This is one easy way to add the text we've shown above (although you can still use your CAD system or Magics as you were before). What you do for Labels in GrabCAD Print is right click a face, type in your label text, and follow the rules laid out above:
Oh, and did we mention that the labels INCREMENT if you make them a label template and then duplicate your models????
That's one of the coolest new GrabCAD Print features in a while. Here is a help article going into more detail about Labels.
Some day I'll do a whole tutorial on how to make labels for all technologies, but for now, play around with this highly requested new feature and please send enhancement requests to print@grabcad.com and shuvom@grabcad.com!
And if color and surface finish HAVE to be consistent, over your ENTIRE model, remember that SAF printed parts can always be dyed after the fact to make them beautiful:
This should allow you to make less restricted decisions about orientation during printing.
And if you ever mess up the orientation or the nesting, know that you can always right click on a 3D nested part to send it back to the 2D Preparation Area, so you can try again:
Okay, that's a lot, lets wrap this up!
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Step 6: Final Thoughts
In summary:
- There's a new technology now available in GrabCAD Print, SAF powder-bed printing
- You'll need a paid license to actually send files to a real printer (but not just playing around with a template)
- It has all the features you're used to in GrabCAD Print PLUS 3D nesting, as long as you
- REMEMBER THE PENGUIN, and
- You can always Manually Nest parts, control spacing and orientation to control surface finish, and dye the parts afterwards, to make them even more beautiful.
There's a lot we've left out about SAF printing that you'll need to go to training for, when you get your new printer, but hopefully this gives you an idea of how to get started in the software.
HUGE thanks to Alec Logeman, our SAF printing expert up in Eden Prairie, for all these tips and pictures- this is Alec's hand holding up our actual finished part!
