Built up edge in CNC turning and milling – the cause, and the solution
Built-up edge (BUE) is not tool wear. Its result is however the same as tool wear – a reduction in the cutting ability of the edge. The workpiece material gets deposited at the cutting edge, replacing the material of the cutting tool and changing its cutting edge geometry. The net effect is that hardness of the cutting edge and the workpiece material are the same, reducing the efficiency of cutting.
BUE results in dimensional inaccuracy and poor surface finish on the part.
The problem occurs when the cutting speed is too low. It can occur with any workpiece material including steels, can occur both in CNC milling and CNC turning and is very common in Aluminium. The workpiece material at the cutting edge softens and attains a plastic (semi-solid) stage, then solidifies on the cutting edge itself. To prevent the problem, the solution is to increase the cutting speed so that the temperature at the cutting edge is higher, the metal being cut takes takes longer to solidify, and solidifies only after it leaves the cutting edge.
Action point
Whenever we encounter a machining problem, our instinct is to reduce the cutting parameters. In Built up edge, do the reverse. Just INCREASE the cutting speed. Also, certain insert coatings and tool materials like PCD (Poly crystalline diamond) reduce BUE.
Text source : CADEM NCyclopedia multimedia CNC training software.
