CNC milling: how to get the right part at the right price

CNC milling is used for everything from simple plates to complex housings and machined castings. The choice of machine and set-up affects both quality and price. Here we explain the most important concepts.

3-, 4- and 5-axis milling

3 axes

The tool moves in X, Y and Z. This is enough for parts machined from one side at a time. If several sides are to be machined, the part must be re-clamped.

4 axes with an indexing table

An indexing table rotates the part so that several sides can be machined in the same set-up. It is an efficient way to reduce re-clamping on parts with holes and surfaces all around. Most of our milling machines have an indexing table.

5 axes

In 5-axis machining, the part can be tilted and rotated at the same time. This makes it possible to reach inclined surfaces and angled holes and to machine complex shapes in a single set-up. Read about 5-axis machining »

Pallet changer: the machine keeps cutting while the next part is loaded

A pallet changer has two tables. While the machine works on one, the operator clamps the next part on the other. The spindle therefore stands still for much less time between parts, giving higher capacity without affecting quality. One of our robot cells is fitted to a pallet machine, which makes it cost-effective even for parts with short cycle times.

What affects the price of a milled part?

• Number of set-ups. Every re-clamping takes time. Indexing tables and 5-axis machining reduce the number.
• Material. Aluminium and brass machine quickly. Steel takes longer and wears the tools more.
• Tolerances and surface requirements. Tight tolerances require more operations and more inspection. Specify tight tolerances only where the function requires them.
• Batch size. Fixtures and programming are one-off costs that are spread over more parts in larger series.
• Geometry. Deep, narrow pockets and small internal radii require small tools and lower speeds.

Design for milling

A few simple choices at the drawing board often make the part cheaper to produce:

• Give internal corners a radius that suits a standard tool.
• Avoid pockets that are unnecessarily deep in relation to their width.
• Group holes and surfaces so they can be reached from as few directions as possible.
• Use standard threads and standard hole diameters.

We are happy to go through the drawing with you and offer tips before production starts.

Do you have a part you want machined? Send us the drawing and we will come back with suggestions and a quote.