CNC Milling Service

CNC milling is a subtractive manufacturing process, 3-axis and 5-axis indexed cutting tools are programmed and managed by computer numerical control (CNC), removing material from the plastic or metal block

CNC Milling design guidelines will help you understand capabilities and limitations.

The components of a CNC mill include: end mill & tool holder (1), tool changer (2), tool carousel (3), spindle (4), 2-axis milling head (5), air/coolant supply tubes (6), fixture (7), work piece (8), tool setter (9), x- and y-axis table (10).

We have multiple tool sets based on efficient cutters for a particular plastic or metal material. The machine then rapidly mills parts out of the block in a subtractive manufacturing process that uses 3- or 5-axis indexed milling.

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

Protolabs’ CNC machining service can deliver machined parts, in both plastic and metal, in less time than it takes to get a quote from other, more traditional machine shops. Upload a CAD file, choose the material and part quantity, and tell us when you need the parts. We also offer number of CNC specific secondary services to support your project.

CNC material data sheets can be found in our Material Comparison Guide

• Good Surface Finishes
• Very Strong (because they use real engineering-grade thermoplastics and metals)
• Fast Parts
• High Accuracy Parts

CNC Milling is a very versatile process that is used in most industries. It is most notable for producing precision parts in particular for automotive and aerospace industries. Parts such as engine components, bushings and exhaust parts. It is also a key service for medical componentry, supporting with prototypes in particular.

It is an important technology in the Oil and Gas industry for key components in extrusion and for Industrial Equipment such as jigs, fixtures tractor parts etc.. This is due to its ability to create complex, accurate, high-finish, high-tolerance parts. It's threading possibilities are also key.

Finally it's high-precision, light weight metals and high-performance plastics make it a popular choice for the aerospace industry for many exterior structural parts and interior parts for bearings, wall panels, ventilation ducts etc. 

CNC milling is often associated with parametric, or cubic designs (and turning with cylindrical) but there is a lot more available:
• Contoured Surfaces - Using a ball end milling cutter and modern CAM software some really complex contoured surfaces are available, even with 3-axis (the kind that you might associate with 5-axis or 3DP)
• Complex Detailing - Engraving and text, by using a small tool, even surface patterns and finishes can produced (often used when producing mould tools)
• Threads, both 3D printing and injection moulding struggle with threads, but CNC can produce 100’s of threads (and is even used to produce inserts used for injection moulding)
• Pockets - These can be used for light-weighting. New design tools for weight optimisation are focused on 3D printing, but they can just as easily be applied to CNC, just remember to design for tool access and add generous fillets.
• Finally walls - Bosses and raised Features can all be created, but remember subtractive (engraved) features like slot slots, channels and holes, are normally more cost effective to machine away.

There are 4 key factors that contribute to your parts, raw material, machine time, labour and speed.

It will be no surprise that some materials are more expensive than others, for metals, steel and aluminium are abundant and have the lowest raw material cost per kg whilst for plastics Acetal, Nylon, Acrylic and ABS tend to work out cheaper.
In the middle of the spectrum for metals you have more specialist aluminiums and stainless steels (containing expensive alloying elements) and for plastic glass-filled grades.
At the high-end you have materials like titanium (which is abundant but difficult to refine) for metal and plastics such as PC, PEEK, PPSU, PEI and POM-ESD, generally required to meet a specific need.

Things such as part complexity and material machinability play a factor here and of course the quicker you want something the more you are likely to pay, remember to compare costs like for like, considering both price and delivery. 

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