CNC machining

CNC machining (Computer Numerical Control machining) is a manufacturing method in which machine tools such as mills, lathes and drills are controlled by a computer program. The program, most often G-code, is generated in CAM software from the CAD model and precisely controls the tool movements and material removal.

CNC machining is the key technology for making precision mechanical parts. It routinely holds tolerances of ±0.01 to 0.05 mm, and tighter ones with special measures. It handles metals (aluminum, steel, stainless steel, titanium, brass) as well as engineering plastics (POM, PA, PEEK), and it suits both prototypes and production runs of parts with critical tolerances.

The core CNC operations are milling (material removed by a rotating cutter), turning (machining rotationally symmetric parts), drilling and threading, and grinding for very precise surfaces. Five-axis machining centers can produce highly complex geometry in a single setup.

The limitations of CNC machining are programming and setup costs (which pay off for production runs or precision prototypes), limited tool access to some areas of the geometry, and the material waste created by removing stock, in contrast to additive manufacturing.

Choose CNC machining when a part has to be made of metal or a specific engineering plastic, has precise functional surfaces (bearing seats, sealing faces, hole patterns) or must have the same properties as the future production part. Typical examples are shafts, flanges, bushings, brackets, frames, jigs and fixtures.

For prototypes, it is the right choice wherever 3D printing cannot meet the requirements for strength, temperature resistance or accuracy. In production, it covers anything from a handful of parts to thousands; larger runs of turned parts often move to bar-fed automatic lathes.

The biggest cost drivers are unnecessarily tight tolerances, deep narrow pockets, sharp internal corners (the cutter is round, so an internal corner radius is always at least equal to the tool radius), thin walls and parts that need many setups. Specify general tolerances according to ISO 2768 and call out tight values only on functional surfaces.

When you request a quote, send both a STEP model and a drawing, and state the material with its exact grade, the quantity, the surface finish (anodizing, zinc plating) and whether the parts must be deburred. Ask whether the supplier provides an inspection report and whether the price includes material and finishing.