One possible approach to solving the problem of unclean knurled profiles is cut knurling. This machining process is increasingly replacing conventional knurl machining that uses forming techniques.
Both straight (RAA) and cross (RGE) knurling to DIN 82 can be achieved with cut knurling tools. In this machining process, sharp-edged knurling wheels are inserted at an angle into the knurling tool holder designed for this purpose. Thanks to their angled position, the sharp-edged knurling wheels are able to remove material from the workpiece in the course of a forward-feed movement, thereby creating the knurl profile.
There are, however, two basic conditions for using this machining process. Cut knurling can only be done starting at the end of the workpiece. It is not possible to knurl in the center of the workpiece. Cut knurling can only be carried out in the centre of the workpiece after a recess has been made. A small chamfer also has to be made at the start of the knurl.
When designing the new product series for knurl milling RGE profiles on Swiss-type automatic lathes, considerable importance was attached to user–friendly adjustment facilities. The workpiece diameter can be conveniently adjusted by means of a central adjusting screw, with synchronous positioning of the knurling tool holders.
For precision adjustment of the knurl profile depth, the positioning of the knurling head can be corrected by means of adjusting screws located at the side.
This machining process also has its advantages when it comes to machining materials that are normally difficult to form. Manufacturers of surgical instruments, for example, prefer to use cut knurling tools because of the high level of optical quality. An additional bonus is the fact that, thanks to the use of carbide bushings, it is possible to achieve very high cutting speeds, thereby saving valuable manufacturing time. With a cutting speed of 30m/min, it has been possible in one particular application by this method, to reduce machining time by around 15%.
Author:
Sigmund Grimm
Vice President Sales & Marketing
s.grimm@hommel-keller.de
HOMMEL+KELLER
Präzisionswerkzeuge GmbH
Uhlandstrasse 4-8
78554 Aldingen
Tel.: +49 74 24 / 9705 – 0
Fax: +49 74 24 / 9705 – 50
www.hommel-keller.de
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