GlossaryKind of term: Manufacturing termCNC machining
What is CNC machining?
CNC machining is removing material with cutting edges on a computer-controlled machine, such as milling, turning, drilling and grinding, to an NC program.
CNC stands for computer numerical control: a control runs an NC program and moves the axes and the spindle, instead of an operator at the handwheel. Machining is the family of processes in which cutting edges remove material as chips. With tools of defined cutting edges that means milling, turning, drilling, tapping and reaming; with undefined cutting edges, such as the grains of a grinding wheel, grinding, honing and lapping. CNC says how the machine is controlled, machining how the material comes off.
How does CNC machining work in practice?
A cost estimate for a machined part is built up from its route: material (the stock, not the finished weight), setup time for each setup, programming, machining time times the machine hourly rate, tooling, deburring, inspection and subcontracted steps such as anodising or hardening. Setup belongs to a batch, programming usually to the part and is reused on repeat orders, and machining belongs to every piece. How you spread that one-off time is an estimating convention. On a single part the one-off time can exceed the machining time, and then the price per piece depends strongly on quantity.
What is CNC machining often confused with?
CNC machining is not CNC programming: the programmer writes the NC program, usually with CAM, and the machine runs it. Nor is it one process: milling, turning and mill-turn each need their own machine, workholding and time build-up. And wire EDM is CNC-controlled but removes material by spark erosion, so in the usual classification it is not a cutting process.
How do you see CNC machining in Blake?
Blake calculates milling from 3-axis to 5-axis, turning, mill-turn, and drilling and tapping. Material, machining, finishing, setup and programming are separate lines, per piece and per batch, at your own hourly rate per machine and with quantity breaks. Every result is labelled as an estimate. More on estimating.
Frequently asked questions
What does CNC machining cost per hour?
It depends on the machine. A 5-axis or mill-turn machine usually has a higher hourly rate than a 3-axis mill. The rate divides depreciation, interest, maintenance, floor space and energy by the productive hours per year. Whether it includes the operator differs per shop.
Why is a one-off CNC part so expensive?
Because setup and programming land on a single piece. In a batch that one-off time is spread over every part; a one-off carries it alone. Machining time per piece changes far less with quantity.
Is CNC machining the same as CNC milling?
No. Milling is one machining process, beside turning, drilling, reaming and grinding. A part can pass through several, for example turned first, then a flat milled and a cross hole drilled, or everything in one setup on a mill-turn machine.