Designing to Minimize Support
- Part 1: some of the basics to consider when choosing a 3D printer.
- Part 2: FDM versus resin printers.
- Part 3: The end to end printing process.
By this point you’ve probably either acquired your 3D printer or you’re zeroing in on the one to buy. Since this series focuses on game designers using 3D printing to prototype game pieces, you’re very likely starting to brainstorm all the cool pawns, miniatures, and accessories you could design. So let’s talk about something you should consider early in the design process — support.
What Is This Support of Which You Speak?
Let’s revisit how the printer constructs a model. I’m going to focus on FDM printers here, but if you’re looking more at resin printers, just know that the support concept applies with those as well.
Take a look at the three models below, being prepped to print by Simplify3D (that’s the slicer I use.) The gray grid is the bed of my printer. The leftmost image is a tile holder I designed for Terraforming Mars. The printer is going to start by dropping a layer of plastic directly on the bed, about 25mm square and .2mm high.
After that first layer, the bed will move down .2mm, and the second layer will be deposited right on top of the first layer. As this process continues and the model grows, every point in every layer is supported by plastic beneath it, all the way down to the bed.
That’s not the case with the warrior in the center image. There are plenty of points where a part of the model hangs out over empty space. (Appropriately, these are called “overhangs” and “bridges.”) The most obvious is that axe. Imagine what happens when the extruder is 2cm above the bed and tries to drop a layer of plastic — that plastic won’t hover in midair at 2cm, it’ll fall to the bed, and your print will fail.
Most slicing programs have a feature called “support generation.” The slicer identifies parts of the model that need to be supported, then builds a thin scaffolding of plastic rising from the bed to the overhang portion of the model, providing support for the model itself. That’s what you’re seeing in the third image, the dark red accordion-like sheets of plastic.
When the print is finishing, you carefully separate these support columns from the model. Your slicer should autogenerate support, but you can also manually place it. In fact, if I wanted to print that warrior miniature I’d have to add some support — there’s no way his left hand can be printed hovering in the air. I’d place some support under the hand, and the arm will grow up from there.
Problems with Support
Support enables prints that otherwise would be impossible. However, you should always choose to avoid support if you can. First, support itself isn’t foolproof. Remember, the support is far more diffuse than the model (typically) and can detach from the bed more easily, or just fail to print. When that happens…you’re back to your original problem.
Next, though your slicer will make the connection point between support and model as small as possible, they ARE still connected. Detaching the support from the model can be delicate work, and may leave rough patches on the model.
Finally, the more support you have, the longer that print is going to take. You can see that in the third image; with the support, there’s a lot more printing to be done.
Maximum Overhang Angle
Not every overhang requires support to print. Each point in a layer doesn’t need to be 100% supported — the new layer can shift considerably from the previous layer and still be supported by that previous later.
This custom pawn I designed for Film Tycoons is a good example. (Alas, Film Tycoons has been put away indefinitely, but designing was a good experience.) See the tripod below the movie camera? The legs are at a shallow enough angle that no support was needed for them. Generally speaking you can print up to 45 degree angles without support, and I regularly go beyond that; I find I can usually print up to 60 degree angles without support.
In fact, that entire pawn is printed without support. “But wait,” you’re probably thinking, “parts of the movie camera are 90 degrees to the bed and unsupported…”
This is my favorite mitigation for support. The movie camera isn’t a single piece, it’s three, and each piece can be printed without support. In the unassembled image you can see the pegs and holes used to put the pieces together. In this case I slightly tapered holes to make the pieces fit together tightly, but you can also use glue or epoxy for a more permanent fit.
There are a few other benefits to designing this way. If I’ve printed my pieces in different colors, I can mix and match to create multi-color pawns easily. Also, should my print fail partway through a piece, I’ve only lost the time on that piece, not on the entire model. That’s not such a big deal with this movie camera pawn, as it prints in just a few minutes, but the concept becomes much bigger when you’re talking about a six hour print.
Rotate the Print
While designing your model to minimize support is great, it’s not always possible to totally avoid the need for support. Slicing programs always allow you to rotate the model to different orientations on the print bed — use that feature to get as much of the model touching the bed as possible.
Great example: boxes. If your box has a lid, the open end should be oriented up, such that no point on the box is unsupported by the model itself. Likewise, when you print the lid, simply flip the lid so the flat side is down, resting on the printer bed. (After all, a lid is just another box with an open side…
And again, modular design. If you’ve designed a fancy box with a hinge, make it printable in parts; top, bottom, and hinge pin. That way each piece can be oriented in a way that minimizes support.
The Han Solo Method
For those with dual extruder printers, PVA plastic can be used in conjunction with PLA to print delicate or organic shapes where support is really just a massive mess. You can surround your model with a block of PVA plastic, which adheres to PLA, but is water soluble. Since this series is for beginners I’m not going to go deep into that method here, but in case there are some more advanced folks reading who want to check out my foray into PVA, here’s a blog I wrote on it in 2016.
Try to design your models in such a way that support is either unnecessary or very minimal. Even with organic shapes this is quite possible. Even that dragon in this blog’s header image was printed with no support whatsoever, due entirely to great design by an artist far more talented than I…
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Until next time…