Kacie Hultgren, aka PrettySmallThings, is a Broadway scenic designer who uses her 3D printer to build scale models for set designs, among other amazing things, like her 3D printed “Clutch Purse” and “Zip Top Bag.” She was also a member of the 2014 Ultimate Guide to 3D Printing testing team.
You can learn more about Kacie from the 5, 4, 3, 2, 1 About Kacie Hultgren maker profile we posted in June.
Kacie’s Top Tips
45 Degree Rule
Remember 45 degree rule, overhangs that are greater than 45 degrees will need support material or you need to use clever modeling tricks to get the model to print. Create your own support / bridging objects (cones and other supports) by designing them into your model.
Design To Avoid Using Support Material
Although support algorithms are improving all the time, support material can leave ugly marks on the outside of your prints. Support material can also be time consuming to remove. Design your models so that they are 3D printable without support.
Add Custom Supports
Use “mouse ears”, helper disks and cones designed into your model to help it print without the use of computer generated supports. Tony Buser’s “Mouse Eared Rocket Fincan” and PrettySmallThings “Windsor Chairs” are excellent example of this design technique. Ditch the raft, it really slows down your prints. Depending on your software / printer configuration rafts can be difficult to remove and also mar the bottom of your prints.
Know Your Printer’s Limitations
Know your model details. Are there tiny towers and small features that are too small to be printed in plastic on a desktop 3D printer? An important, but often overlooked, variable in what your printer can achieve is thread width.
Thread width is determined by the diameter of your printer’s nozzle. Most printers have a 0.4mm or 0.5mm nozzle. Practically, this means that a circle drawn by a 3D printer is always two thread widths deep: 0.8mm thick with a 0.4mm nozzle to 1mm thick for a 0.5mm nozzle. As Kacie states in the video, the rule of thumb is “The smallest feature you can create is double the thread width.”
Fit Tolerances for Interlocking Parts
For objects with multiple interlocking parts, design in your fit tolerance. Getting tolerances correct can be difficult. Kacie’s tips for creating correct tolerances: use a 0.2mm offset for tight fit (press fit parts, connecters) and use a 0.4mm offset for lose fit (hinges, box lids). You will have to test it yourself with your particular model to determine what is the right tolerance for the thing you are creating.
Use Shells Properly
Don’t use additional shells on fine featured models, like small text. It will obscure the detail.
Optimize for Thread Width
Use thread width to your advantage. If you are making flexible models or need very thin features, design the walls of your model to be one thread width thick. Check out Hultgren’s collection of “Flexible Inspiration” model collection on Thingiverse for more examples on utilizing this technique.
Orient for the Best Resolution
Always orient your model for the best resolution possible for that particular model. Models can be sliced into pieces if necessary and then re-assembled. On Fused-Filament Fabrication printers, you can only control the Z resolution. The X and Y resolutions are determined by thread width. If your model has fine features, make sure the model orientation is cable of printing those features.
Orient for Stress
To keep prints from breaking when force is applied; make sure to orient your model to minimize stress on the part by orienting the model so that the print lines are perpendicular to point of the pressure being applied.
The same principle applies to ABS, which when used to print large models, can split along the Z-axis as they cool on the build platform during printing.
The “Holy Grail”: Print and Place Designs
Print in place designs that contain multiple integrated parts, are the “Holy Grail” of FFF desktop machines. Here are Hultgren’s tips on how to tackle “print in place designs”: pull design elements to platform, use bridges for captive parts and gap print carefully.
Watch the video for more details and context. Do you have tips on designing for 3D printing? Share them with us!
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