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CNC Machining
CNC machining prototype parts
CNC machining is versatile for producing prototype parts in metals, alloys and engineering plastics. Quick and cost-effective, CNC (computer numerical controlled) machining is more accurate than 3D printing parts, so is excellent for functional prototypes.
Typically, we CNC machine parts that will be manufactured by other processes once they are in mass-production. In addition, we CNC machine one-off final parts and small batches for special-purpose machine builders and manufacturers of low-volume, high-value products.
If you are unsure whether CNC machining is right for your part, ask us for an unbiased opinion because we also have 3D printing technologies in-house.
CNC milling and turning of prototype parts
We have invested heavily in our CNC machining department in terms of machinery and staff, enabling us to fulfil orders quickly. Find out more about our CNC milling and CNC turning capability.
What tolerances can be held when CNC machining prototype parts?
Our general quoted tolerance is ±0.1mm, which is considerably better than for 3D printed parts. In reality, CNC machining is usually accurate to much less than ±0.1mm, and critical dimensions can be held to tight tolerances on request.
CNC machining and the benefits of isotropic material properties
CNC machining has a key advantage over some 3D printing technologies in that material properties are isotropic, which can be vital for functional prototypes. Whereas 3D printing with SLS tends to result in parts that are stronger in the X and Y axes than the Z axis, CNC machining from solid materials ensures mechanical properties are uniform in all directions.
Production speeds for CNC machining
Our CNC machining service is built around flexibility. Lead times are tailored to your project and our in-house capacity, and we’ll confirm what’s achievable when you request a quote.
We also offer a 3-day service, subject to your part meeting our 3-day criteria.
Learn more on our Production Speeds page.
Finishing options for CNC machined prototype parts
Where possible all CNC machined parts are vapour honed to produce a cosmetic, aesthetically pleasing finish. Other finishes available for metal and plastic parts include painting, plating and polishing. For metal parts, finishing can include specialist treatments to improve hardness or surface friction, as well as aesthetics and corrosion resistance. More information is provided on our CNC machining finishing options page.
Inspection of CNC machined parts
If your part has key dimensions, we check these with callipers and micrometers. Unlike many other prototyping companies, we also have a co-ordinate measuring machine, so we can take more measurements and produce detailed inspection reports. Read more about our in-house inspection facilities.
CNC machining workflow
When you send us an enquiry with an X_T, STEP or IGES CAD file, we check it, raise any queries, then prepare a quote. We do not need 2D drawings unless you need to highlight critical dimensions, tolerances or other special features. If you accept the quote, we schedule the job, prepare the CNC program and reserve the material from our stocks or source it as necessary. Machine setups are quick thanks to our paperless process, so we can start cutting material as soon as possible. Finished parts are deburred, cleaned, degreased and inspected. Any additional finishing operations are then carried out. Finally, your parts are packaged and dispatched, using our electric van for local delivery or a courier for customers further afield.
Other materials are available (subject to supplier lead times).
CNC 3-Day production speed criteria
If you want your CNC machined part dispatched in 3 working days, your part must meet all of the criteria detailed below. If your part does not meet the criteria, you will need to choose one of our other production speeds.
Milling
Your part needs to fit into one of these billet sizes:
- 150mm x 50mm x 40mm
- 100mm x 100mm x 80mm
- 100mm x 100mm x 40mm
- 100mm x 50mm x 40mm
- 50mm x 50mm x 40mm
Parts can be made from:
- Aluminium 6082
- Acetal (black and natural)
- Clear Acrylic
Turning
- 60mm max dia in Aluminium 6082
- 60mm max dia in Acetal (black and natural)
- 60mm max dia in Clear Acrylic
- 60mm max dia in Stainless Steel (316/304)
Numerous types of metal and plastic material can be machined using CNC machining. We keep a stock of commonly used materials in-house. Only the materials listed below, are available on our CNC Express service. If you require different materials, you will need to choose one of our other CNC service levels.
- Acetal – black and natural
- Acrylic – clear
- Aluminium – 6082
All machined parts are vapour blasted, as standard. Other finishes are available on request, but will need to be ordered using one of our other CNC service levels.
Threaded holes of M2 – M12 (model drill hole size) are supported on our CNC Express service. Standard threads only. For through tapped holes make hole size suit drill Ø M1-M12. See the diagram below for details.
Drill depth clearance for blind holes:
As a natural result of the CNC machining process, the sharp inside corners of a part will be rounded (radiused). The resulting radii will be identified before the part is milled as this will depend on the depth of the feature.
Sharp corner concession:
Here are some considerations, should your part incorporate text:
- 0.5mm is the minimum stroke width for recessed text
- 0.5mm, or greater, spacing should be used between characters on raised text
- Recessed text is better than raised text
- General machining tolerance: ±0.1
- Hole tolerance: H7
- Number of items and quantity of limited (geometry specific)
- Maximum of five separate parts may be included in one quote request
- Inspection: basic visual to CAD
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Talk to us
Do you need CNC machined prototype parts? Talk to us about your project on 01763 249760 or complete the enquiry form below to request a quote.
CNC Machining FAQ
What is CNC Machining?
CNC (Computer Numerical Control) machining is a subtractive manufacturing process that produces parts by cutting material away from a solid block using computer-controlled machines. It’s ideal for producing accurate, functional parts in a wide range of materials.
What materials can you machine?
Numerous types of metal and plastic material can be machined using CNC machining. We keep a stock of commonly used materials in-house, including:
- Aluminium alloy 6082
- Stainless steel, AISI grade 304
- Stainless steel, AISI grade 316
- Acetal (Delrin)
- Acrylic (PMMA)
Other materials are available quickly from our suppliers including a large array of different engineering plastics. If you’re unsure which material is best, our team can advise based on performance, finish and function.
What are the advantages of CNC machining compared to 3D printing?
CNC machining is well-suited to parts that need high accuracy, excellent surface finishes or strength in production-grade materials. 3D printing is often used for complex geometries and rapid turnaround, while CNC machining delivers precision parts with robust mechanical properties.
What tolerances can you achieve?
Our general quoted tolerance is ±0.1mm. In reality, CNC machining is usually accurate to much less than ±0.1mm, and critical dimensions can be held to tight tolerances depending on the material and geometry. We always check your drawings and requirements before machining.
What is the maximum size you can machine?
For our low volume production work and 3-day production work, we typically use our 5-axis VMCs. These machines are configured to handle two main billet sizes: 150mm x 100mm x 90mm and 150mm x 50mm x 40mm. However, we can accommodate smaller parts with a range of billet sizes available.
We also have a wide array of 3-axis machines which can produce parts up to approximately 450 x 350 x 150 mm, subject to geometry. See our Plant List for full details.
If in doubt, it’s best to speak to us about your specific needs.
How quickly can you deliver CNC parts?
We typically offer flexible production speeds for CNC parts, depending on part complexity and quantity, as well as our capacity at the time. Timescales will be confirmed as part of the quotation / ordering process.
Can I get my parts anodised or plated?
While we do not offer in-house plating and anodising services, we do have a sub-contractor that we work closely with to ensure you receive the finish you are looking for. Common requests are black, clear and hard anodising, surtec 650 and nickel plating. Other finishes are available on request just contact us on 01763 249760 for more information.
What is vapour honing and do you offer it?
Vapour honing is a type of finishing that can be applied to parts after the machining process to both clean and provide a more uniform surface finish. It is a technology that involves blasting the part with a mix of abrasive material and pressurised water. It is effectively a ‘wet’ version of dry blasting however the water softens the blow of the material and washes dirt and debris away.
We vapour hone CNC machined parts as standard unless instructed not to, or it is not suitable for your part.
Can I free issue material for quotation/production?
Yes, we can machine free issue material. This is dependent on part geometry and material, but please contact us to discuss your needs.
What finishes can be applied to my CNC parts?
Typically, all CNC parts are vapour honed as standard to give a more aesthetically pleasing part. We also offer an extensive range of finishing options for CNC parts including EMI/RFI shielding on plastic parts. We have in-house facilities for both wet painting and manual polishing. Other processes, such as anodising and powder coating, can be subcontracted to local specialists.
Browse our finishing options.
Can CNC machining be used for tooling?
Yes. Our CNC expertise underpins not only the production of standalone parts, but also the manufacture of mould tooling for our injection moulding service. This gives us complete control over tool accuracy, timescales and modifications.
What industries use your CNC machining services?
We provide CNC machining for clients in medical, aerospace, automotive, consumer products and more — for both prototypes and production-quality parts.