Why should I consider CNC machining when there is Additive Manufacturing?

Why should I consider CNC machining when there is Additive Manufacturing?

3D Printing or Additive Manufacture can achieve some great results, especially if time is very limited but does that make it the best choice? 

Part size vs part complexity

If your part is large and simple (in relation to its size) then certainly consider CNC machining but, if your part is small and intricate, then additive manufacture may well be better suited. 

There is no concrete hard and fast rule - there are some features that may be challenging to produce with machining but can be realised easily through additive manufacture.

Likewise, there are important design considerations for additively manufactured parts that must be taken into account, such as the placement of support material and tight tolerances that may make the part difficult to produce.

Surface finish and Material Choice

3D Printed parts by their nature will be made in layers and on curved surfaces these can appear as steps. To achieve a good surface finish these will need to be post processed out. 

CNC machining, however, works in a minimum of three simultaneous axes with the result being a smooth, accurate surface straight from the machine.

Materials are usually process specific for 3D Printing, whereas the list of options for CNC Machining are huge. 


Additive manufacture can produce prototype or low quantity runs very quickly, with little or no tooling. However, this process is less suited to larger quantities due to the time spent on expensive-to-run machinery. 

CNC machining allows you to produce finished prototype parts without post processing, which can make this a cost-effective option if it suits your finish requirements. Low runs and larger quantities become even more viable due to the set-up time being utilised across the numbers (we have machined up to 100,000 parts). 

CAD Modelling

Parts should be designed with the manufacturing method in mind, although obviously there will be design features which cannot be changed as they perform critical functions. 

A good designer will have a method of manufacture in mind as they design a model, so they optimise the part for that particular process. We can help you with this as this preparation is crucial to avoid delays in production. 

CNC machining is a viable option

A CNC prototype therefore has a lot to offer, especially if the goal is for an excellent surface finish. In addition, CNC machining can be cost competitive, frequently allowing a ‘finished’ part to be delivered for the same price as a ‘raw’ 3D printed part.

We offer both CNC machining and additive manufacturing processes and therefore are completely unbiased and will be totally honest as to the best solution for your part. For further support and advice please pick up the phone and talk to us.

Find out more about Plunkett Associates on their member profile page here

Member-created content 2 months ago | Members' news

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