Free resource
DFM checklist for FDM parts
27 points we check before a part goes into production. Work through the list before you send an RFQ to avoid rework, warping and unnecessary cost.
Walls and ribs
- Walls are at least 1.2 mm (3 perimeters at 0.4 mm) for structural parts.
- Wall thickness is a multiple of the extrusion width so no thin gap-fill lines are needed.
- Ribs replace solid volume instead of thickening the whole wall.
- No wall thinner than 0.8 mm anywhere in the part.
Load direction and orientation
- Main load runs across layers, not along the Z axis, wherever possible.
- Thin cantilevers, clips and hooks are not built standing up in Z.
- Cosmetic faces are identified so we can orient them away from supports.
Holes, threads and fasteners
- Holes that need accuracy are marked for reaming or drilling after printing.
- Vertical holes are drawn 0.1 to 0.2 mm oversize to compensate for shrink.
- Load-bearing threads use heat-set inserts or nut pockets instead of printed threads.
- Screw bosses have at least 2 mm of material around the insert.
Overhangs and geometry
- Overhangs stay under 45 degrees, or are chamfered instead of squared.
- Bridges are shorter than 30 mm, or supported by a rib.
- Sharp internal corners have a small fillet to reduce stress risers.
- Large flat areas are broken up or have a chamfered base to limit warping.
Tolerances and fits
- General tolerance expectation is plus or minus 0.3 mm, or 0.3 percent on long dimensions.
- Only the features that truly matter are tightly toleranced on the drawing.
- Mating parts have a defined clearance, typically 0.2 to 0.4 mm for sliding fits.
Material and environment
- Maximum service temperature is known and the material is chosen above it.
- Outdoor or UV exposure is flagged so ASA or PA is used instead of PLA or ABS.
- Flame retardancy, chemical contact and food contact requirements are stated up front.
Cost and production
- Part fits the build plate without splitting, or split lines are already designed in.
- Support-heavy internal geometry is redesigned or made accessible for removal.
- Quantity, delivery date and repeat order plan are communicated with the RFQ.
- File is exported as STEP where possible, or as a fine-tolerance STL.
Not sure about one of the points?
Send us the file. We review the geometry, point out the critical areas and suggest a suitable material before you order.