Model design rules for SLS/MJF 3D printing

Different 3D printing processes have different capabilities and different design restrictions. In this article we will talk about key design considerations that apply to all 3D printing processes.

Here are 7 tips I have found helpful when designing and modeling for 3D prints. these tips should work on most 3D modeling software.

Keep Your Parts Manifold
For modelers coming from animation, illustration, or gaming backgrounds, one important thing to remember is that your 3D prints must be composed of watertight manifold volume parts. Always check your model for artifacts, loose faces or unwelding edges and verts.

That means:
No one dimensional planes,shells or extruded edges
No double sided faces
No self intersecting faces
No open faced holes
No unwelded verts or edges

Multi-object Prints
Does my part need to be one continuous mesh? This is a question that many new modelers have when creating for 3D printing. The simple answer is that a continuous mesh is not required. You can design prints from overlapping or intersecting objects so long as all components involved are manifold parts.

Know Your Build Area
When designing your part, keep in mind your build area. However, your printer’s build volume does not have to limit the size of your final model. Be creative! Clever layout in your build area can help you get larger prints. For instance, the diagonal space from top to bottom in your build area will give you the longest build size of your printer.

Small prints and exaggerated details
When sculpting small parts, it’s often very helpful to slightly exaggerate details. This means making your surface details with slightly deeper cuts and more pronounced surface texture. If possible, making slender parts slightly thicker will help ensure that they will print clean.

Save Material
Making your model hollow using shell and boolean functions available in your modeling software will save you resin material. Be sure to make a large enough “vent hole” that connects to your hollowed area to the outside of your model this will allow uncured material to flow out.

Clean Up Well
After your print is finished you have to soak your finished print in IPA for 12-15 minutes. I find that towards the end of the soak you can give your part a gentle rubdown with your gloved hand to help break down and remove any resin stuck to the surface of your print. Using a soft brush also helps to reach area that you can’t reach with your hand, this added step this helps get a quality finish to your print.

Remove Supports Carefully
Take your time when removing your support material. Rushing this process could ruin an otherwise flawless print. Using an X-acto knife to score a line at the connection point will give a cleaner break. Give thicker supports a gentle wiggle, don’t pull or use excessive force.

Especially for SLS/MJF,How do you design for SLS/MJF printing?

General guidelines for designing SLS/MJF parts are as follows:

Wall thickness
To ensure a successful 3D print, minimum thickness should be between 0.8mm (for PA12) and 2.0mm (for carbon-filled polyamide).

Hole size
All holes should be larger than 1.5mm in diameter.

Escape holes
To save in weight (and sometimes cost), SLS parts are printed hollow. To remove unsintered powder after production, it is necessary to include escape holes, which must be a minimum of 3.5mm in diameter.

Feature size (pins, protruding features, etc.)
A minimum of 0.8mm is recommended.

Embossed and engraved details
To ensure small details are visible: – make minimum engraving depth 1mm. – make minimum embossing height 1mm.

Text
For readability: – ensure minimum font height is 2mm (font size 14) and suitable for every direction. – sans serif font is recommended.

Tolerances
Typical tolerances for SLS parts are ± 0.3mm or ± 0.05mm, whichever is greater.