Model Design Rules for 3D Printing

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

Here are seven tips we have found helpful for 3D printing designing and modeling for 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! A 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 helpful to exaggerate details slightly, making your surface details with slightly deeper cuts and more pronounced surface texture. Making slender parts slightly thicker will help ensure they print clearly.

Save Material

Making your model hollow using shell and boolean functions available in your modeling software will save you resin material. Make a large enough “vent hole” that connects your hollowed area to the outside of your model for 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. You can use a soft brush to clean the cracks. This step 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, and don’t pull or use excessive force.

Especially for SLA, How do you design for SLA printing?

The detail level an SLA printer can produce depends on laser spot size and resin properties. General guidelines for designing for SLA are as follows:

Supported Walls

These walls are connected to other structures on at least two sides (so they have a very low likelihood of warping) and should be designed at a minimum of 0.4mm thick.

When the connection is less than two sides, the walls have a high chance of warping or detaching from the print. These walls must be at least 0.6 mm thick and should be designed with filleted bases (where the wall connects to the rest of the print) to reduce stress concentrations along the joint.

Overhangs

Unless the model is printed without adequate internal and external support structures, overhangs pose little issue with SLA printing. Printing without supports often leads to warping of the print, but if it is necessary to print without supports, any unsupported overhangs must be less than 1.0mm for longness and at least 19° from level.

Embossed Details (including text)

These features on the model, which are raised slightly above the surfaces around them, must be at least 0.1mm above the surface to ensure the details are visible.

Engraved Details (including text)

If too small, the features imprinted or recessed into the model are at risk of fusing with the rest of the model during printing. Therefore, the details must be at least 0.4mm wide and 0.4mm thick (the distance from the model surface to the recessed detail).

Horizontal Bridges

These bridges between two points on a model can be successfully printed. But wider horizontal bridges must be shorter (less than 21mm) than thin bridges. Wider bridges have a larger z-axis connection area, increasing the chance of print failure during peeling.

Holes

The holes would seal off during printing when their diameter is less than 0.5mm in the x-, y- and z-axes.

Connections

Use 0.5mm clearance between moving parts.

Use 0.2mm clearance for assembly connections.

Use 0.1mm clearance to give a push or snug fit.