DFM Guide - CNC Tools

1. Internal Corner Radii

CNC milling cutters are round. Therefore, sharp 90-degree internal corners are impossible to machine directly.

Pro Tip: Always design internal corners with a radius at least 10% larger than the cutter's radius. For example, if you design a corner with a 3mm radius, we can cut it quickly with a standard 5mm tool.

2. Minimum Wall Thickness

Very thin walls decrease part stiffness and can cause severe vibration or warpage during cutting.

Material Category	Recommended Min Wall	Absolute Limit
Metals (Aluminum, Steel)	0.8 mm	0.5 mm
Plastics (ABS, POM, PEEK)	1.5 mm	1.0 mm

3. Deep Pockets and Cavities

Deep cavities require long tools which are susceptible to deflection and vibration (chatter).

Limit pocket depth to **4x the pocket width**.
Avoid deep internal cavities with steep walls that cannot be reached by standard straight mills.

4. Tapped Holes & Threads

Tapping threads requires proper pre-drill diameters and depths:

Use standard metric thread sizes (M2, M3, M4, M5, M6, M8, M10, M12).
Blind Hole Rule: Thread depth should not exceed **3x the nominal hole diameter**. Make sure to leave extra space at the bottom of a blind hole for the tap tool tip.

CNC Checklist

Internal corner radii ≥ 3mm

Wall thickness ≥ 0.8mm

Pocket depths ≤ 4x width

Standard metric threads specified

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1. Minimum Feature & Wall Thickness

For additive layers, minimum limits vary significantly depending on the technology:

SLA (Resin): Minimum wall thickness is **0.8mm** for supported features, **1.0mm** for unsupported pins or cantilever structures.
FDM (Filament): Minimum wall thickness is **1.2mm** to allow double toolpaths. Absolute minimum pins are **1.0mm**.
MJF (Nylon): Minimum wall thickness is **1.0mm** for reliable sintering.

2. Overhangs & Support Angles

Overhangs are sections of a print that do not have active layers directly underneath them:

45-Degree Rule: Overhangs with angles greater than 45 degrees from the vertical plane require supporting scaffolds. To eliminate cleanups and cost, design self-supporting angles (chamfers or fillets) under horizontal features.

3. Clearances & Tolerances

For interlocking geometries or assemblies printed together:

Leave a minimum gap of **0.3mm to 0.5mm** between moving parts.
If parts are intended to fit tightly post-assembly, include a clearance margin of at least **0.15mm** to accommodate print shrinkage.

4. Escape Holes for Hollow Parts

SLA and MJF technologies use liquid resin or powder beds. To print hollow spheres or boxes, you must include drain/escape holes to prevent trapping materials inside:

Include at least **two escape holes** with a minimum diameter of **3mm** near the base.

3D Print Checklist

Walls ≥ 1.0mm thickness

Overhang angles ≤ 45 degrees

Moving gaps ≥ 0.4mm clearance

Drain holes added on hollow parts

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