3D Printing Wall Thickness and Tolerance Chart (FDM, Resin, SLS/MJF).

This chart gives starting values for minimum wall thickness, holes, clearances, overhangs and fine detail for FDM, resin (SLA/MSLA) and nylon powder (SLS/MJF) 3D printing. They are typical values from manufacturer design guides. Every printer and material behaves slightly differently, so print a small test piece before you commit to a tight-fitting assembly.

3D printing wall thickness and tolerance chart

Sources for typical values: Hubs design considerations and Hubs SLS design guide. For help choosing between processes, see FDM vs SLA vs SLS vs MJF.

Wall thickness

On FDM printers, make walls a whole multiple of the line width, which is usually the nozzle diameter. With a 0.4 mm nozzle, use 0.8 mm (two lines), 1.2 mm (three lines) or 1.6 mm and above for load-bearing parts. In-between values leave thin gaps inside the wall.

Keep wall thickness as even as possible. Thick sections next to thin ones cool at different rates and can warp FDM parts or leave sink marks on SLS and MJF parts. On powder-bed parts, hollow out sections thicker than about 4 mm and add escape holes so the powder can be removed.

Overhangs and bridges: the 45° rule

On FDM, each layer needs something underneath it. Faces tilted up to 45° from vertical print cleanly without supports. Between 45° and about 60°, they still print but the underside gets rougher. Beyond about 60°, add supports or change the design.

• Use a 45° chamfer instead of a fillet on edges that touch the build plate. A fillet starts almost flat and droops; a chamfer prints cleanly from the first layer.
• Turn horizontal holes into teardrop shapes, or accept a little roughness at the top of the hole.
• Bridges between two supports print well up to about 10 mm with good part cooling. For longer spans, add an arch or a gusset.

Resin parts almost always need supports, so orient them so support marks land on hidden faces. SLS and MJF parts need no supports at all.

Holes, fits and clearances

FDM prints small vertical holes slightly undersize, typically 0.2 to 0.4 mm smaller in diameter, because the plastic contracts as it cools. Either model the hole larger or drill it to size after printing. For an 8 mm guide rod, model the hole at 8.3 mm, or print it at 7.8 mm and ream it with an 8 mm drill.

• Sliding or rotating fit (FDM): 0.3 to 0.4 mm clearance per side.
• Sliding fit (resin): 0.15 to 0.2 mm per side.
• Bearing press fit (FDM): start with a hole 0.1 to 0.2 mm larger than the bearing's outer diameter, print a test ring, and adjust.
• Snap fits: use PETG, nylon or tough resin. PLA and standard resin tend to crack.

Strength and load direction

FDM parts are weakest where layers meet, so a part is stronger when the load runs along the printed lines rather than pulling layers apart. Orient brackets so the bending load lies in the build plane. For strength, add perimeters (wall lines) before increasing infill: four walls with 25 to 35% gyroid infill are usually stronger than two walls with 80% infill.

Avoid sharp inside corners. Add fillets of 1.5 to 3 mm to spread stress, especially where a rib meets a wall.

Screws and threads in printed parts

Printed threads wear out quickly if a screw is removed often. Better options:

• Brass heat-set inserts: size the hole to the insert maker's specification and press the insert in with a soldering iron.
• Captive nut pockets: hexagonal slots that hold a standard M3, M4 or M5 nut.
• Through-bolts: a bolt through the whole part with a washer and lock nut.

Preventing warping on large flat parts

Large flat FDM parts lift at the corners when the edges cool faster than the middle. Round the outside corners, use a brim, keep the bed at the right temperature for the material and protect the printer from drafts. ABS and ASA usually need an enclosed printer.

Frequently asked questions