Introduction

Designing high-quality CNC machined parts requires a balance between functionality and manufacturability. At MILE Precision, we’ve seen how minor design adjustments can significantly reduce lead times and production costs. To help you get the best results from your CNC projects, we’ve compiled 5 key Design for Manufacturing (DFM) tips.

1. Define Critical Tolerances Only

While high precision is our specialty, unnecessary tight tolerances can drive up costs.

• Pro Tip: Standard CNC machining typically holds a tolerance of ±0.1mm.
• Only apply tighter tolerances (e.g., ±0.02mm) to critical mating surfaces or bearing bores. This ensures your part functions perfectly without overcomplicating the manufacturing process.

2. Simplify Geometry & Internal Radii

Sharp internal 90-degree corners are impossible to machine with rotating drill bits.

• Design Fix: Always add a fillet (radius) to internal corners.
• A good rule of thumb is to make the corner radius slightly larger than the tool’s radius to reduce tool stress and improve surface finish.

3. Maintain Uniform Wall Thickness

Consistent wall thickness is vital to prevent warping and ensure structural integrity during the milling process.

• For Metals: Aim for a minimum wall thickness of 0.8mm to 1.5mm.
• For Plastics: Maintain at least 1.5mm to 2.0mm to avoid deformation due to heat or clamping pressure.

4. Optimize Hole Depths and Threading

Deep holes are challenging because they require specialized long tools that are prone to vibration (chatter).

• Depth Limit: Keep the hole depth within 4x the diameter.
• Threading: Avoid threading all the way to the bottom of a blind hole; leave a small unthreaded gap to prevent tool breakage.

5. Choose the Right Material for Your Application

Material choice affects everything from cutting speed to tool wear.

• Aluminum (6061/7075): Best for cost-effectiveness and speed.
• Stainless Steel (304/316): Ideal for corrosion resistance but requires slower machining.
• Engineering Plastics (POM/PEEK): Excellent for insulation and lightweight parts.