Design guidelines for 3D printing
Seven basic rules that apply to almost every process – followed by the most important guide values for FDM, SLA and SLS at a glance.
Seven rules that almost always apply
Sufficient wall thickness
Walls that are too thin become unstable, warp or are missing altogether. Depending on the process, plan at least 1–1.5 mm, more for loaded parts.
Avoid or chamfer overhangs
Surfaces that overhang flatter than about 45° need supports in FDM and SLA. A 45° chamfer instead of a horizontal edge saves supports and finishing.
Horizontal holes as teardrops
Large horizontal holes sag at the top. FDM usually prints them cleanly up to about 9 mm in diameter; above that, a teardrop shape with the tip pointing up helps. Drill or ream for fits.
Clearance for moving parts
Parts that move or interlock need clearance. Without it they fuse together. Guide value: FDM at least 0.1–0.3 mm, SLS 0.3–0.5 mm laterally and 0.5–0.6 mm vertically.
Radii instead of sharp inside corners
Sharp inside corners concentrate stress – that is where a part cracks first. A small radius distributes the force and also helps against warping.
Open up cavities
In SLS, powder – and in SLA, liquid resin – remains trapped in closed cavities. Provide openings: at least 2 mm for SLA, larger for SLS.
Avoid material accumulations
Solid areas cool unevenly and warp. Ribs or lattices are almost as stiff and save material and print time.
The underestimated rule: how is the part oriented?
Printed parts are anisotropic – they are not equally strong in every direction. In FDM, a part is much weaker across the layers than along them.
Force along the layers
Orient the part so that the main load acts in the layer plane – not so that it pulls the layers apart.
Visible surface facing up
The side that must look good faces up or sideways. Undersides and support surfaces show marks.
Curves in the plane
Holes and curves are most accurate in the print plane. Vertical holes are rounder than horizontal ones.
The most important values per process
| Feature | FDM | SLA | SLS |
|---|---|---|---|
| Minimum wall thickness | approx. 1.2 mm | over 1 mm | 1.0 mm (safe 1.5 mm) |
| Overhang without supports | up to approx. 45° | supports almost always needed | no supports needed |
| Unsupported bridge | up to approx. 2 mm without support | up to approx. 0.5 mm | any |
| Clearance for moving parts | from 0.1 mm, safe 0.3 mm | from approx. 0.3 mm | 0.3–0.5 mm laterally, 0.5–0.6 mm vertically |
| Holes / pins | horizontal up to approx. 9 mm without support | holes over 1 mm | pins from 1.2 mm |
| Tolerance | ±0.2 mm up to 100 mm, otherwise ±0.15 % | very tight, depending on resin | depending on geometry |
| Cavities | possible, without opening | Drain holes larger than 2 mm | openings for depowdering |
| Threads | better use threaded inserts | fine threads possible, inserts are better | printed from approx. M6 |
Guide values for typical components. Material, machine and geometry may vary – if in doubt, we check your model before printing.
Screws, clips and fits
Consider the material in the design
Not sure whether your model is printable?
Send us the file. We check wall thicknesses, overhangs and fits and tell you what we would change.