As a Stratasys applications engineer, I spend my days intimately involved with our technology. It’s exciting to design complicated parts and push the limits of the technology. When designing for 3D printing, you need to keep in mind a couple key factors to improve the quality of your builds.
Those factors are:
- Tolerances
- Wall Thickness
- Support Removal
- Forces
The quality and design freedom will also vary based on the machine you use to print. I will break down the key factors for four of the Stratasys machines that I know best to give you an idea of what is possible and where limitations lie.
You will need to make sure to add the specified tolerances to any moving parts, otherwise the part may print stuck to itself. Each 3D printing technology and machine has its own precisions this info will define the tolerance distance depending on geometry. Moving parts clearance should be 3 -4 times the build resolution of your machine,the FDM system like a Fortus 380 or an uPrintSe plus (e.g. FDM build Resolution: 0.01’’. moving parts: 0.03-0.04’’ clearance).
Let's start with tolerances
Here are some tolerances for the machines I work with:
Fortus 380 – build resolutions include .005’’, .007’’, .01’’, and .013.’’ Typical achievable tolerance +/- .005 1st in.; +/- .001 every in. after
uPrintSE plus – uPrint build resolutions .01" or .013." For uPrint system there is no standard tolerance. Dimensional accuracy will vary based upon part size, geometry, and orientation. These systems are designed to produce concept 3D models which do not typically require accuracy down to a few thousandths of an inch. Todd Grimm & Associates performed a benchmark study of 3D printer accuracy that you can check out.
Stratasys PolyJet – Between +/- 0.2mm .(006” to .009”) for features less than 2” Up to +/- .008” for very large features
What about Wall Thickness?
I’m glad you asked! The minimal wall thickness recommended will also change based on geometry, but typically we recommend two toolpaths (roads) thickness for FDM and .025’’ in wall thickness for PolyJet. Also keep in mind that the wall height will also affect the minimum recommended wall thickness, make no wall taller than 6-8 times its thickness.
Fortus 380 – Please see chart on default road thickness. Remember, minimum wall thickness should be two roads.
uPrintSE plus – For .01’’ resolution, minimum wall thickness of .04.’’ For .013’’ resolution, minimum wall thickness of .052.’’ we recommend you to have a minimum thickness of 3mm (.1’’)
Stratasys PolyJet – .5mm (.02’’) but be aware that these walls will be weak so be careful not to break them when removing support
MakerBot – minimum wall thinness (0.42 mm) .02’’ we recommend you to use .9mm (.04’’) [in the MakerBot desktop use number of shells 2]
And then there is the topic of support
Parts printed with internal support must have ample access to remove support (i.e. no enclosed hollow structures). If possible, put access holes on at least two opposing sides to allow for removal fluid flow when printing with machines with soluble support. Avoid support in tight spaces or corners.
With breakaway support, be careful designing thin walls or features so you do not break them when removing support. In general, it is a best practice to orientate parts on the build tray to minimize the amount of support or decrease the difficulty of removing it.
Fortus 380 – Water soluble support
uPrintSE plus – Water soluble support
Stratasys PolyJet–removed with a pressurized water, or soluble support
MakerBot – Break away support, removed by tools
I know these tips and tricks are specific to the printers I know best, but as you design for any machine I encourage you to think about tolerances, wall thickness, support, and forces. Good luck with the challenge, we can’t wait to see what you come up with!
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Editor's Note: Ohad Meyuhas, a Stratasys applications engineer, developed the content for this blog post.
