Design Guide

File formats

STL, STEP and 3MF files are accepted. STEP and 3MF files are converted to STL in your browser before upload. A 3MF with several objects is priced as one part containing all of them; upload separate files to order them separately.

STL files have no units, so they're read as millimeters. If an STL part shows up 25× too small, it was exported in inches. STEP and 3MF files carry their own units and are converted automatically.

Models must be closed solids (watertight). Surfaces and open shells can't be printed.

Part size

Each part's dimensions are shown next to it after upload. If a part is too large to print in one piece, you'll get a message instead of a price. Split it into pieces that fit together, or contact us.

Wall thickness

• Aim for walls at least 1.2 mm thick; 2 mm or more for parts that take load.
• Thin pins and posts under about 3 mm diameter are fragile. Thicken them or add fillets at the base.
• Very thick solid sections aren't needed. Parts are printed with an internal infill pattern.

Tolerances and fit

• Typical FDM accuracy is a few tenths of a millimeter. Don't count on press fits straight off the printer.
• Leave about 0.3–0.5 mm clearance between parts that slide or snap together.
• Holes tend to print slightly small. For a precise hole, size it a little undersize and drill or ream it to final size.
• Need tight tolerances? Machining is the better process: quote it on Subtract.

Strength and orientation

Printed parts are strongest along their layers and weakest between them. Parts are oriented for good print quality; if a specific direction must carry load, mention it when you contact us about a production run.

Overhangs and supports

Overhangs steeper than about 45° from vertical need support material, which leaves marks where it's removed. Chamfers instead of flat overhangs, and teardrop-shaped horizontal holes, print cleaner.