How to Design Parts for 3D Printing: 10 Tips from Engineers

Design Better Parts, Get Better Results

3D printing can make almost anything — but “can” and “should” are different things. These 10 tips will help you design parts that print successfully, function properly, and cost less.

1. Minimum Wall Thickness

For FDM: 1.2mm minimum (2 perimeters). For SLA: 0.8mm minimum. Going thinner risks failed prints or fragile parts. If you need thin walls, consider SLA or PolyJet over FDM.

2. Design for the Orientation

3D printed parts are strongest along the print layers (X-Y plane) and weakest between layers (Z direction). Orient critical load paths along the layers, not across them. This single decision can make a 5x difference in part strength.

3. Avoid Large Flat Surfaces

Large flat surfaces on the build plate tend to warp, especially with ABS. Add chamfers, fillets, or ribs to break up flat areas. If you must have a flat surface, orient it vertically.

4. Support Structure Strategy

Overhangs beyond 45° need support material. Support removal leaves rough surfaces. Design your part so that critical surfaces face up or sideways, not down. Better yet, design self-supporting geometry — use teardrop holes instead of circular holes for horizontal through-holes.

5. Hole Sizing

3D printed holes tend to print 0.1-0.2mm undersized. If you need a precise hole, design it 0.1-0.2mm oversize or plan to drill/ream to final size. For press-fit holes, test with your specific printer and material first.

6. Clearance for Assemblies

Design 0.2-0.3mm clearance between mating parts for FDM. SLA can work with 0.1-0.15mm. Test-fit early — it’s cheaper to reprint one part than to redesign an entire assembly.

7. Infill and Strength

You don’t need 100% infill for strong parts. 25-40% infill with 3-4 perimeters gives you 80-90% of the strength at 40-50% of the cost and print time. Increase wall count (perimeters) before increasing infill — perimeters contribute more to strength.

8. Add Draft Where Possible

Even though 3D printing doesn’t require draft angles like injection molding, adding 1-2° draft to vertical walls improves surface quality and makes parts easier to post-process. If you might switch to injection molding later, designing with draft now saves a redesign.

9. Consolidate Parts

One of 3D printing’s superpowers is part consolidation. An assembly of 5 bolted-together parts can often become a single printed part. Fewer parts = fewer failure points, less assembly labor, and lower cost.

10. Include Reference Features

Add datum surfaces, alignment pins, or reference flats that let you measure and verify critical dimensions. This is especially important for functional prototypes that need to interface with other components.

Need Help with Your Design?

PartSnap’s engineers review every file that comes through our shop. If we spot design issues that will affect print quality or part function, we’ll flag them — free of charge. Submit your design for a free review and quote.