3D print tolerances for parts that fit together

By Let's 3D Studio · 1 min read

A dimension in CAD is the beginning of a fit, not the final guarantee. FDM parts can vary with material, orientation, cooling, line width, and the condition of the machine. The most useful tolerance is one you have tested on the printer and material that will make the final assembly.

Design a small tolerance coupon with the same style of peg, slot, thread, or sliding surface that matters to the product. Print it in the final material and orientation, then record the clearance that gives the intended feel. Repeat when the material, nozzle, or profile changes.

For critical assemblies, design for adjustment. Captive nuts, screws, thin shims, and replaceable interfaces can make a print easier to tune than a single irreversible press fit.