GlossaryKind of term: Manufacturing termMachining time
What is machining time?
Machining time is the time the machine spends running the program per part: cutting plus rapids and tool changes, excluding loading and unloading.
It consists of the cutting time, when the tool actually removes material, plus whatever the program does in between: rapids, tool changes and any probing. Loading, clamping and unloading are outside it; add those and you have cycle time in the broader sense used in estimating and planning. Usage varies: some shops mean cutting time only, others the whole time per operation. State in an estimate which boundary you use.
What does machining time depend on?
Cutting time per pass follows from path length and feed rate. In milling the feed rate is feed per tooth times number of teeth times spindle speed, in turning feed per revolution times spindle speed. The number of passes follows from depth and width of cut. Which cutting data are achievable depends on material, tooling, tool overhang, the stiffness of part and setup, and the machine's power and speed limits. Requirements can raise the time without changing the shape: a low roughness often calls for a smaller feed in finishing, a thin wall for lighter cuts.
How does machining time work in practice?
On batches, machining time often weighs most in the cost. A machine is also occupied during loading, unloading and measuring, though; multiply only machining time by the machine hour rate and that share is missing. The same pocket usually takes longer in 1.4404 stainless steel than in 6082 aluminium, through lower cutting speeds and a smaller removal rate. Calculated in advance it remains an estimate; a time from CAM or the machine is more accurate, but applies to one particular program.
What is machining time often confused with?
Machining time is not cycle time: cycle time also counts loading, clamping and unloading. Nor is it cutting time: cutting time is only the time the tool removes material. And machinability describes how readily a material machines with given tooling and conditions; machining time is one of its consequences.
Frequently asked questions
Why does machining time differ by material?
Because achievable cutting speed, feed and depth of cut differ. Stainless steel, titanium and hardened steels generally need lower cutting data than aluminium or free-cutting steel, so more time for the same volume.
How do you estimate machining time before there is a program?
From the volume to remove and the features, with cutting data for the material and an allowance for rapids and tool changes. That gives an estimate; a CAM calculation or a measurement on the machine is closer to reality.