Prototyping Via Machining Will Always Have Its Place

CNC machining will continue to be used for prototyping work by shops that see value in offering such a service to their customers.


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Surely you’ve noticed that we cover additive manufacturing from time to time. Such CAD-to-component technologies have proven valuable for rapid prototyping purposes and may soon be used in more production applications, as this lead story for our April 2011 issue suggests. That said, there are two truths when it comes to additive manufacturing as it will be applied in machine shops.

Truth 1: Additive manufacturing will never completely replace CNC machining.

Truth 2: CNC machining will remain the best, if not the only, alternative for a number of rapid prototyping applications.

Additive manufacturing excels in generating net-shaped or near-net-shaped parts with very complex geometries. However, the equipment faces limitations in terms of process speed, maximum part size and choice of materials, not to mention that some machining may still be required to create threads and other features after a part is printed or sintered. It also might not be able to provide the smooth surface finish needed for certain prototyping applications because it builds parts in layers (albeit very tiny ones).

In the end, additive manufacturing technologies will prove to be complementary to CNC machining, even when it comes to prototyping.

I’ve profiled a number of shops that view prototyping via CNC machining as an important part of their overall business approach, even if they aren’t prototype shops per se. They feel the service helps pave the way to new customers while cultivating relationships with existing ones. They also believe it puts them in a better position to win any follow-up production work.

Although there’s no guarantee that a shop will win subsequent production work, many still approach prototyping with a production mindset. They don’t dash off a prototype using a machining method that would be impractical for production. This way, customers know exactly what the true cost of the production part will be, eliminating any unfortunate surprises.

In addition, by running prototypes through production machines, it’s possible to work through issues that are only revealed during a production run. This also minimizes “re-learning” because all aspects of the production machining process—tooling, workholding, programming and cutting data—have been established.

Still, some shops don’t pursue prototyping work, which is understandable when it’s clear no production run will develop. However, shops continue to implement strategies to help set themselves apart from others, and those that offer services such as prototyping could very well lure customers away from others that don’t.