If you study CNC machining and 3D printing in detail, there are many small but important differences. These differences can... Continue reading
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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 FDM, SLS or Polyjet 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.
Service levels for CNC machining
Depending on your technical requirements and project timescales, we offer three service levels: Express, Standard and Economy, with parts shipped in as little as three days for our Express Service. We never compromise on quality to achieve the rapid turnaround of the Express service or the lower cost of the Economy service. Find out more about the Service Levels and Dispatch times on our Service Levels page.
Finishing options for CNC machined prototype parts
Different finishes are available for metal and plastic parts, such as 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 the paperless process we have developed, 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 despatched, using our own vans for local delivery or a courier for customers further afield.
Other materials are available (subject to supplier lead times).
CNC Express – criteria
If you want your CNC machined part dispatched in 3 working days, your part must meet all of the CNC Express criteria detailed below. If your part does not meet the criteria, you will need to choose one of our other service levels.
Maximum Material Stock Size (3-axis milling) (Your part must fit within the stock size)
Milling
- 250mmx200x50 max size in Aluminium 6082
- 250mmx200x50 max size in Acetal (black and natural)
- 250mmx200x30 max size in Clear Acrylic
- 100mmx100x12 max flat bar size in Stainless Steel (316/304)
- 50mmx50x25 max square bar size in Stainless Steel (316/304)
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
- Stainless Steel – 316 & 304
All machined parts are left as-milled. 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 FAQs
What is CNC machining?
CNC machining is used to produce incredibly accurate, high-quality parts with an excellent finish.
The CNC services we offer mean prototype tools can be injected in-house and production tools can be run by our subcontractors or supplied to you for moulding. We can also provide a full range of tool refurbishment.
Read more about CNC Machining.
What material is used for CNC parts?
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.
Read more about CNC Machining.
What service levels are available for CNC parts?
We offer three service levels for CNC machining:
- Express: 3 working days – subject to criteria
- Standard: 7 working days
- Economy: 12 working days
Read more about our service levels.
What finishes can be applied to my CNC parts?
The standard finish we offer on CNC parts is as machined. This simply involves removing all sharp edges but leaving patterns left by the tool as it has removed the material. We can remove these machining marks by scotchbiting or sand blasting the part at your request. Parts can also be plated, anodised or even painted once machined.
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 an 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 do not currently offer vapour honing as a process but this is something we will be looking into in the near future.
Can I get my parts anodisied or plated?
We do not currently offer in house plating and anodising services but 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 the Office Team on 01763 249760 for more information.
What tolerance can you hold on CNC machined parts?
Our general machining tolerance is +/-0.1mm when no engineering drawings are supplied. However when drawings are supplied parts can be machined to an accuracy of +/-0.01 depending on material and part geometry. If you have any specific requirements then highlight them to the Office Team at the quote request stage.
What is the maximum part size that you can CNC machine?
We have an array of different machines that all offer different bed sizes. However, our largest bed size is 450mm x 375mm, meaning we can’t machine any parts bigger than this in-house.
Can you modify existing parts?
Yes we can modify free issued parts depending on your exact requirements and part geometry.
Can I free issue material for quotation/production?
Yes we can machine free issue material. Again this is dependent on part geometry and material but please feel free to discuss with our Office Team on 01763 249760.
CNC Machining team
Our CNC machining team produce accurate, high quality parts with an excellent finish from our suite of CNC machines. Request a quote for your next prototype part.
Ian Reinemann
Senior CNC Manager
Greg Gorman
Assistant CNC Manager
Oli Fensome
Programmer
David Brassington
Quality Inspector
Michal Mikolajczyk
CNC Operator / Setter Shift Supervisor
Glenn Watts
CNC Operator / Setter
Edwin Simkins
CNC Operator / Setter
Dan Summerfield
CNC Operator / Setter