GlossaryKind of term: Manufacturing termMaterial removal rate (Q)
What is the material removal rate?
Material removal rate Q is the volume of material an operation removes per minute, given in cm³/min and calculated from the cutting data.
Each process has its own formula for Q, with the cutting data in their usual units. In milling, Q = ap × ae × vf / 1000, with axial depth of cut ap and radial width of cut ae in mm and table feed vf in mm/min. In turning, Q = vc × ap × f, with vc in m/min, ap in mm and feed f in mm/rev. A cutter at ap 10 mm, ae 6 mm and vf 1,000 mm/min removes 60 cm³/min. The figure belongs to one cut under fixed conditions; it is not a property of the machine.
What does the material removal rate depend on?
The Q you can reach depends on spindle power and torque at the speed in use, the stiffness of machine, workholding and part, tool overhang, the tool itself and the machinability of the material. Cutting power rises roughly in proportion to Q and to the specific cutting force kc, which depends on the material, chip thickness and edge geometry: as an approximation Pc ≈ Q × kc / 60,000 in kW, with Q in cm³/min and kc in N/mm². That is the power at the cutting edge; spindle power has to be higher because of drive efficiency. That is why the same machine can reach a far higher Q in aluminium than in stainless steel. Chip evacuation can be the limit too. Averaged over a whole toolpath, the removal rate is lower than the Q of the cut itself, because of varying engagement, entry moves, retracts and rapids.
How does the material removal rate work in practice?
Without CAM, roughing time is often estimated from the removal rate: the volume between stock and finished shape divided by an average Q that suits the machine, material and strategy. That is an estimating convention, not a measurement, and the result is only as good as the Q you choose. For finishing, holes, threads and small corner radii, volume says little: surface area, path length and the number of features and tools set the time. A part with little volume and many features can come out too low on a volume estimate alone. A realistic average Q comes best from your own programs or measured times.
What is the material removal rate often confused with?
Removal rate is not machinability: Q is the rate of an operation, machinability a property of the material that helps decide which Q is achievable. Nor is it the volume of chips in the bin: loose chips take up many times the volume of the material removed, which matters for chip handling and disposal, not for machining time.
Frequently asked questions
How do you calculate removal rate in milling?
Q = ap × ae × vf / 1000, in cm³/min: depth of cut times width of cut in mm, times table feed in mm/min, divided by 1000. In turning Q = vc × ap × f, with vc in m/min and f in mm/rev.
How do you estimate roughing time without CAM?
Divide the volume to be removed by an average Q your machine reaches in that material. Add finishing, holes and tool changes separately. It remains an estimate, and its quality depends on the Q you choose.
Where do you get a realistic removal rate?
Preferably from your own programs: removed volume divided by the measured or simulated time of a roughing operation that ran well. Cutting data from a tool supplier give the Q of one cut under favourable conditions, not an average over the whole path.