Shenzhen Alu Rapid Prototype Precision Co., Ltd.

How It Works

CAD Model → CAM Software → G-Code → CNC Machine → Finished Prototype

Step by Step:

1. Create 3D CAD model (Fusion 360, SolidWorks, etc.)

2. CAM software generates toolpaths and G-code

3. CNC machine follows code to cut the part

4. Operator inspects and finishes the part

Types of CNC Milling for Prototypes

Common Materials for Prototype CNC Milling

Metals:

Plastic

Prototype CNC Milling vs Other Prototyping Methods

Advantages of Prototype CNC Milling

• ✅ High accuracy — tolerances down to ±0.01mm

• ✅ Real production materials — test with actual metal or plastic

• ✅ Excellent surface finish — close to production quality

• ✅ Strong functional parts — can withstand real testing

• ✅ Wide material choice — metals, plastics, composites

• ✅ No tooling required — unlike injection molding or die casting

• ✅ Fast turnaround — 1–5 days typically

• ✅ Design validation — confirm fit, form, function before production

Disadvantages

• ❌ Higher cost than 3D printing — especially for complex parts

• ❌ Material waste — subtractive process removes a lot of material

• ❌ Geometry limitations — can't make internal cavities easily

• ❌ Undercuts require 5-axis — adds cost

• ❌ Minimum wall thickness — limited by tool diameter

• ❌ Setup time — programming and fixturing adds cost

Typical Applications

Automotive

• Engine brackets and housings

• Suspension components

• Interior trim prototypes

• Jigs and fixtures

Aerospace

• Structural brackets

• Hydraulic components

• Interior panel prototypes

• Test fixtures

Medical

• Surgical instrument prototypes

• Implant models

• Medical device housings

• Orthopedic component testing

Consumer Products

• Electronic device housings

• Mechanical component testing

• Ergonomic evaluation models

• Pre-production samples

Industrial

• Machine component prototypes

• Custom tooling

• Replacement parts

• Assembly fixtures

Prototype CNC Milling Process in Detail

1. Design Phase

• Create fully dimensioned 3D CAD model

• Add machining-friendly features (draft angles not needed)

• Define tolerances and surface finish requirements

• Choose material

2. CAM Programming

• Import CAD model into CAM software

• Define stock size (billet dimensions)

• Select cutting tools (end mills, drills, etc.)

• Generate and simulate toolpaths

• Export G-code to machine

3. Setup

• Mount raw material block in vise or fixture

• Load correct cutting tools

• Set work coordinate system (zero point)

• Verify first cuts carefully

4. Machining

• Roughing passes — remove bulk material fast

• Semi-finishing passes — approach final shape

• Finishing passes — achieve final dimensions and surface finish

• Drilling and tapping holes

5. Post-Processing

• Deburring sharp edges

• Surface finishing (polish, anodize, paint)

• Dimensional inspection

• CMM measurement if tight tolerances required

Design Tips for CNC Prototype Cost Reduction

• ✅ Avoid deep narrow pockets — hard to reach, slow to cut

• ✅ Use standard hole sizes — match standard drill bit sizes

• ✅ Add generous fillets — sharp internal corners require small slow tools

• ✅ Minimize setups — design parts machinable in 1–2 setups

• ✅ Loosen tolerances where function allows

• ✅ Avoid very thin walls — under 0.5mm adds cost and risk

• ✅ Standard surface finish unless critical areas need better

Typical Cost and Lead Time

When to Choose Prototype CNC Milling

Choose CNC milling when you need:

• Functional testing with real materials

• Tight dimensional tolerances

• Metal prototype specifically

• Surface finish close to production

• Strong structural prototype

• Fit and assembly verification

Choose 3D printing instead when:

• Speed is most important

• Budget is very tight

• Geometry is too complex for milling

• Functional testing not required

• Early concept validation only