To CNC or not to CNC?

By Jonathan Wilkins, Marketing Director, EU Automation

The capabilities of 3D printers are growing and engineers are now using the equipment to print food, houses and even human organs. In industry, both 3D printing and CNC machining allow manufacturers to rapidly produce complex, strong and lightweight parts but sometimes it can be difficult to know which technology will better suit an application. This article discusses the applications for CNC machining and additive manufacturing.

3D printing and CNC machining are both computer-controlled technologies that can produce complex parts from a variety of materials. The key difference between them is that 3D printing is a form of additive manufacturing, where material is added one layer at a time until the final component is built. On the other hand, CNC machining starts with a block of material, which is gradually removed by a cutting or milling tool until the part remains.

There is no evidence that one technology is better than the other, so it might be difficult to know which one is appropriate when designing a new product. However, there are some situations where one will perform better than the other and manufacturers should look at a range of factors to decide which technology to use.

Materials

Metal additive manufacturing (AM) creates products using metal powders, made from materials such as stainless steel, aluminium or titanium alloy. Metal 3D printing allows manufacturers to create complex parts that are strong and lightweight.   Despite its many advantages, metal 3D printers can be costly for manufacturers.  If the designer is not sure whether AM is the best solution long term, they can turn to a bureau to order a prototype part, before deciding what equipment to invest in.

Manufacturers can invest in a CNC machine for a more cost-efficient technology. CNC machines can   machine parts from durable materials such as stainless steel or aluminium or less durable materials such as wood, foam or fibreglass. If your design requires wood or foam, this may rule out 3D printing.

Despite its versatility, design engineers should be aware that CNC machining will require more material because it starts with a larger block and removes material throughout the process. 3D printing only uses the material required for the product, reducing material costs and waste.

Complexity

As CNC machining starts with one solid block of material, manufacturers are limited in the intricacy of a design. They can only cut or mill areas that the drill or lathe can access and designing custom tools can be a lengthy and expensive process.

Manufacturers should use metal 3D printing if they want to produce a part with high geometric complexity. Additive manufacturing has fewer design constraints and no need for custom tooling, which means it can produce extremely complex geometries, such as lattices. During the design process, support structures are important to ensure a complex part can be produced properly.

Scalability

Both CNC machining and 3D printing allow manufacturers to move from the design process to manufacturing quickly. They simply need to put the design on a computer-aided design (CAD) file and upload it to the machine. However, CNC machining can be a faster process, which often makes it the best choice for a larger production scale of heavier, less intricate products. 3D printing is ideal for small batches of custom products due to its flexibility.

While manufacturers will not be mass-producing replacement organs anytime soon, they have now the ability to quickly manufacture complex parts. Manufacturers will be able to produce most parts using CNC machining, because it is cost-efficient, accurate and scalable. In applications that require more creativity, complexity or personalisation, manufacturers should look to 3D printing.

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