Material removal rate

The material removal rate follows from the width of cut, the depth of cut and the feed rate together. It measures how hard an operation works, not how accurately it works.

What it means for the calculation

In roughing this is the main driver of time: the faster the excess material is gone, the shorter the operation. The achievable value is limited by the machine's power and rigidity, by the material, and by how stiff the fixture is. A small part cut from a large block is mostly roughing time, so it pays to look at the stock size before pricing the features. In finishing this figure says little: there, the roughness requirement and the tolerance set the time.

Where this comes up

In the shop program and in work preparation's time standards, not on the drawing. The drawing steers it indirectly, through the material and through how much material has to come off.

Common mistakes

Carrying the value of an aluminium part over to a tough alloy; that difference is large and makes a calculation worthless in one step. Also taking the machine builder's figure without weighing the fixture: a flexible setup will not reach that value.

What unit is it given in?

Usually cubic centimetres per minute.

Is a higher value always better?

For roughing usually yes, as long as the machine, the tool and the fixture can take it.

Does it say anything about accuracy?

No, that is a different question; finishing is about tolerance and roughness, not volume.