CNC Milling Service

Get custom milled parts for rapid prototyping and production.
Certifications ISO 9001:2015 | CTQ Inspections | ISO 13485

Our CNC milling process produces custom prototypes and end-use production parts in as fast as 1 day. We use 3-axis milling and 5-axis indexed milling processes to manufacture parts from more than 30 engineering-grade plastics and metals. With machined production parts, you can also get more competitive pricing at higher quantities in addition to first article inspection (FAI) reporting, material certifications, and additional finishing options like anodizing and chromate plating. 

Our CNC milling service is commonly used for:

  • functional prototypes
  • jigs and Fixtures
  • production components in lower volumes

CNC Milling Design Guidelines and Capabilities

Our basic guidelines for CNC milling include important design considerations to help improve part manufacturability, enhance cosmetic appearance, and reduce overall production time. View our design guidelines page for more details.

Maximum Dimensions
Maximum Dimensions

Maximum depth that can be milled is 2 in. (50.8mm) from either side of part. For specific milling dimensions by material, see maximum part extents for machining.

  Material US Metric
3-axis**
  • ABS
  • Acetal
10 in. x 14 in. x 1.75 in. 254mm x 356mm x 44.5mm
3-axis**
  • ABS
  • Acetal
  • Nylon
22 in. x 14 in. x 0.75 in. 559mm x 356mm x 19.1mm
3-axis**
  • Aluminum 
22 in. x 14 in. x 3.75 in. 559mm x 356mm x 95.3mm
5-axis
  • Hard metals*
  • Brass
10 in. x 7 in. x 1.75 in. 254mm x 178mm x 44.5mm
5-axis
  • Copper
10 in. x 7 in. x 2.75 in. 254mm x 178mm x 69.9mm
5-axis
  • Aluminum
  • Plastic
10 in. x 7 in. x 3.75 in. 254mm x 178mm x 95.3mm


*Hard metals: Titanium (6Al-4V), Stainless Steels (303, 304, 316, 17-4PH), Alloy Steel (4140)

**Denotes two-sided machining only

Minimum Dimensions

Minimum Dimensions

  US Metric
Size 0.25 in. x 0.25 in 6.35mm x 6.35mm
Nominal Thickness 0.040 in. 1.02mm
Threading
Threading

We currently support UNC and UNF threads from #2 up to 0.5 in., and metric threads from M2 to M12. Avoid modeling internal threads on your part design.

We also offer the following for milled parts:

  • Coil inserts
  • Key inserts
View Threading Options
Tolerances Typically, Protolabs can hold a machining tolerance of +/- 0.005 in. (0.13mm). Part features are recommended to be thicker than 0.020 in. (0.51mm) in all regions and a nominal part thickness above 0.040 in.
Radii Sharp inside corners on a part will be radiused (rounded) as a natural result of the CNC machining process. Resulting radii will be identified on your quote.
Text Plastic and soft metals: Minimum width of 0.018 in. (0.457mm), depth of 0.0118 in. (0.3mm). Example text size would be 16 point Arial Rounded MT font. Hard metals: Minimum width of 0.033 in. (0.838mm) and depth of 0.0118 in. (0.3mm). Example text size would be 22 point Arial Rounded MT font. If design permits it, opt for recessed text versus raised

CNC Milling Materials

We stock more than 30 production-grade plastic and metal materials that are suitable for various part applications and industries.

Metals
 
 
 
  • Aluminum
  • Brass
  • Copper
  • Stainless Steel
  • Alloy Steel
  • Steel Mild Low Carbon
  • Titanium

Anodizing and Chromate Plating Specifications

Anodize Hard Anodize Chromate

MIL-A-8625 Type II, Class 2 (Blk)

MIL-A-8625 Type II, Class 1(Clr)

MIL-A-8625 Type III, Class 2 (Blk) MIL-DTL-5541 Type II, Class 3 (Clr)

Quick-turn Finishing

Here are the requirements to get parts in as fast as 4 days (1-day expedite + 3 days for plating):

  • Aluminum 6061/6082 and 7075 material eligibility
  • Threaded holes plugged
  • No masking available

High-requirement Finishing

Have AS9100 and ITAR requirements? Try our domestic precision machining option. If you have more complex anodizing and plating requirements, work with our digital network of manufacturers. The network works well for components that require a specialized color or material option such as titanium or nickel.   

Surface Finish on Milled Parts

Typically, we break (debur) the edges on all machined parts. All machined plastic parts are left as-machined, which may leave visible tool marks. Some metal parts, on the other hand, allow more choice. Parts left with sharp edges should be handled with care.

Tour our Digital Machine Shop

Take a quick tour through our 215,000 sq. ft. CNC machining facility in Minnesota to see how we manufacture parts in as fast as 24 hours. 

What is CNC Milling and How Does it Work?

CNC milling is a subtractive manufacturing process. It starts by fixturing a block of metal or plastic material inside the CNC mill. Using G-code, the CNC machine is programmed to rapidly mill out parts from the block of raw material. Our 3- and 5-axis CNC machines are equipped with various toolsets to maximize efficiency and production speed.

Machined plastic parts are left as-milled, which typically means they show visible tool marks. Some metal parts allow more finishing choices like anodizing and chromate plating. When the run is complete and your required surface finish is applied, parts are boxed and shipped shortly thereafter.

Additional Links and Resources

11 Tips to Reduce Injection Molding Costs

Stretch your budget with these injection molding design recommendations. Quick hint: Simplify!

How to Use Mold Flow Analysis

Flow analysis helps decide gate placement, locate knit lines, and find areas where gas can get trapped.

Glass Transition Temperature of Polymers

Glass transition temperature (Tg) affects moldability, strength, elasticity, transparency, and more.

Beginner’s Guide to Injection Molding

Learn what product designers must consider when designing a part for injection molding, including: warp, surface finish, stress, resin additives, and more.

Ready to Start Your Project?