What Tolerances Can 3D Printing and CNC Machining Achieve? A FAQ Guide

Dimensional tolerance -- how close a manufactured part's dimensions are to the design specifications -- is one of the most technical yet important aspects of custom manufacturing. This FAQ covers tolerance capabilities across different 3D printing and CNC machining processes.

CNC machining offers the tightest tolerances among common manufacturing processes. CNC Milling (3-axis) achieves +-0.01mm to +-0.05mm for general precision parts. CNC Milling (5-axis) delivers +-0.01mm to +-0.03mm for complex geometries. CNC Turning provides +-0.005mm to +-0.025mm for cylindrical parts and shafts.

3D printing tolerances vary significantly by technology. SLA (Resin) achieves +-0.1mm to +-0.3mm -- the best accuracy of all 3D printing methods. SLS (Nylon) delivers +-0.2mm to +-0.5mm consistent across all directions. FDM (Plastic) provides +-0.2mm to +-0.5mm depending on part orientation. DMLS (Metal) reaches +-0.1mm to +-0.3mm varying by metal alloy.

• Part orientation -- XY plane (flat on build plate) is most accurate; Z axis has slight stair-step effect
• Part geometry -- Large flat surfaces may warp; tall thin walls may deflect
• Material shrinkage -- Different materials shrink at different rates (SLS nylon ~2-3%, SLA resin ~0.2-0.5%)
• Thermal effects -- Cooling gradients cause residual stress and warping in some materials
• Wall thickness -- Thin walls can deform during printing or post-processing

No. Over-specifying tolerances increases cost and lead time unnecessarily. Only specify tight tolerances for features that must fit with other parts (interference/clearance fits), are critical for functional performance, or will be used as reference surfaces for assembly. For all other features, use standard tolerances (+-0.1mm for SLA, +-0.3mm for SLS/FDM).

Use GD&T (Geometric Dimensioning and Tolerancing) notation when you need specific tolerances on specific features. Indicate general tolerance in your notes (e.g., "General tolerance: +-0.3mm unless otherwise specified"). Call out critical dimensions explicitly with tighter tolerance values. Note if a surface needs to be particularly smooth or flat. Include any assembly requirements such as press-fit holes.

Yes. Hybrid manufacturing combines 3D printing with CNC machining. Print the part with standard 3D printing tolerances, then CNC machine critical surfaces to tighter tolerances in a secondary operation. This approach is common in aerospace and tooling applications.

Not sure what tolerances your design requires? PrintVX engineering team reviews every order for manufacturability and can recommend appropriate tolerances. Upload your design at PrintVX.com for a free DFM review.