How to Prepare CAD Files for 3D Printing

Good Files Make Good Parts

Most printing problems that surprise customers were visible in the file before the printer ever moved. Five minutes of export discipline prevents nearly all of them. This guide covers the formats we accept (STL, STEP, OBJ, 3MF, IGES), the export settings that matter, and the pitfalls that produce faceted curves, missing features, or unprintable geometry.

Choosing a Format

The practical differences:

STL Export Settings That Matter

STL approximates your curves with triangles, and the export tolerances decide how faithfully:

• Chordal deviation (linear tolerance): 0.01-0.02mm. Coarser shows visible flat facets on curved surfaces; finer bloats the file without visible benefit.
• Angular tolerance: 5-10 degrees for smooth curvature flow.
• Binary STL, not ASCII — identical geometry at a tenth of the file size.
• Export at 1:1 scale and note your units. STL carries no unit information; a 25mm cube and a 25-inch cube are the same numbers. Our upload flow detects improbable sizes and asks, but stating units removes all doubt.
• One body per file unless parts are meant to print as an assembly.

The Watertight Requirement

A printable mesh must be watertight (manifold): every edge shared by exactly two triangles, enclosing a single unambiguous volume. The classic violations — holes in the surface, zero-thickness walls modeled as bare surfaces, self-intersecting shells, duplicated faces — make a part's volume undefined, and slicers either fail or guess. Our upload pipeline analyzes every file and reports open boundaries, non-manifold edges, and degenerate faces rather than guessing, so problems surface at upload time, not after a print attempt. The reliable fix is upstream: model solids, not surfaces, and run your CAD's own check (most have one) before export.

Common Pitfalls We See Weekly

The recurring ones, so you can skip them:

• Faceted curves from default-coarse STL exports — set the tolerances above.
• Unit confusion: a file authored in inches read as millimeters is 25.4x too small. State units in the order.
• Features below printable size: text under 0.8mm wide, walls under 3 layer-widths, pins under 1.5mm diameter — they vanish or crumble. Check the minimums for your process.
• Assemblies exported as one fused mesh when separate parts were intended.
• Mesh-repair artifacts from auto-fix tools that welded intentional gaps shut — repair changes geometry; review what it did.

Upload and Verify in Seconds

The fastest verification is the upload itself: our pipeline parses your file, reports geometry problems in plain language, shows measured dimensions for a sanity check, and prices the part instantly. STEP files from parametric CAD skip the whole faceting question — when in doubt, send STEP.