Built-up edge
A built- up edge is an artificial edge on processing tools , which is formed by "material caking". It arises when machining tough materials especially for relatively small cuts and high feed rate mainly on the chip , but also on the free surface of the tool. The built-up edge is made possible by the smallest material particles , which build up in layers through pressure welding and adhesive phenomena to form a larger accumulation of material. This is so hardened that it can take over the function of the cutting edge.
The built-up edge changes the geometry of the cutting wedge to a cutting wedge with a small angle and a large positive rake angle. The material that builds up on the cutting edge protrudes beyond the cutting edge, breaks off from time to time and is carried along by the chip flowing away.
Such a cutting approach should be avoided as it has various disadvantages:
- The constant assembly and dismantling of the built-up edge causes vibrations. Until the built-up edge tears away and the original edge engages, the cutting force decreases. This results in fluctuating cutting forces which, under poor conditions, can lead to premature tool breakage.
- When the built-up edge is sheared off, parts of the cutting edge usually break off, so that tool wear occurs more intensely .
- The built-up edge can tear open the workpiece surface and adversely change the structure ( blank braking ).
- The changed cutting edge geometry leads to dimensional errors on the workpiece, the tool setting must be corrected.
The formation of built-up edges can be reduced by:
- Reduction of the cutting speed
- Use of coated cutting materials
- Smooth, lapped rake faces as well as low-notch cutting edges
- Abundant use of cooling lubricants
- Cutting materials with increased thermal conductivity
- Transition to tools made of hard metal
- Enlargement of the chip cross-section (higher feed rate and / or greater cutting depth)
- Use of a cutting edge with a positive rake angle
Web links
- Machining of metallic materials - built-up edge formation - IMF educational film with film recordings of the formation of built-up edges in slow motion.
literature
- Martin Molitor, Karl-Heinz Grote, Horst Herold, Bernhard Karpuschewski: Introduction to manufacturing theory (= reports from the Institute for Manufacturing Technology and Quality Assurance, Magdeburg . Volume 8 ). 2nd Edition. Shaker Verlag , Aachen 2008, ISBN 978-3-8322-6647-9 , p. 147 ff .
Individual evidence
- ^ Warnecke, Günter and Hummel, Günter: Machining of metallic materials - built-up edge formation. In: av.tib.eu. Retrieved September 13, 2019 .