GlossaryKind of term: Manufacturing termMicro-machining
What is micro-machining?
Micro-machining is milling, drilling and turning very small features, typically with tools less than a millimetre in diameter.
The features range from a few micrometres up to about a millimetre, cut mechanically with small end mills and drills or with fine turning tools. There is no fixed boundary; definitions in the literature differ. In the broad sense, micro-EDM and ultrashort-pulse laser machining are counted in the field too. Applications include medical devices, optics, electronics and moulds for small plastic parts.
What makes micro-machining different from ordinary machining?
At this scale the rules of thumb from ordinary machining no longer hold. The chip thickness per tooth can be of the same order as the cutting edge radius; below a minimum chip thickness the material is pushed aside rather than cut, which leads to burrs and a poorer surface. Runout of spindle and toolholder loads the cutting edges unevenly and raises the risk of breakage. High spindle speeds are needed to reach a usable cutting speed. Thermal growth of the machine, the accuracy of tool measurement and the material's microstructure, such as grain size, weigh more heavily than on larger parts.
How does micro-machining work in practice?
In micro-machining the time often sits less in the material removed than in everything around it: low feeds, warm-up until the machine is thermally stable, tools that can break without warning, inspection with optical equipment or a CMM with a small stylus, and deburring under a microscope. An estimate built on cutting time alone can therefore fall well short; by how much depends on material, features, tolerances and machine.
What is micro-machining often confused with?
Micro-machining is not ultra-precision machining: micro is about the size of the features, ultra-precision about form accuracy and roughness, on large surfaces too. The two can coincide, but a micro channel can carry ordinary tolerances and a large mirror can be ultra-precise. Nor is it precision engineering in general, the broad trade of small precision parts, which mostly runs on standard tooling.
Frequently asked questions
When do you call it micro-machining?
When cutting features up to about a millimetre, such as fine channels, small holes and mould cavities, with tools below a millimetre in diameter. There is no fixed boundary; definitions vary by source.
What machine do you need for micro-milling?
A high-speed spindle with low runout, a thermally stable machine and environment, and tool measurement that records the true length and diameter. An ordinary machine with a high-speed spindle attachment can handle part of the work.
How do you measure micro features?
With optical equipment such as a measuring microscope or a vision system, and for 3D form a CMM with a small stylus or an optical profiler. On this work inspection can take a large share of the total time.
When should you use a laser instead of micro-milling?
For structures smaller than the smallest usable cutter, for hard or brittle materials and for surface textures. With ultrashort pulses the heat input stays low, but the walls are often slightly tapered.