Bar peeling is heavy-duty machining in every respect

Bar peeling is one of the most demanding of all machining operations and good process engineering know-how of the actual working area is of crucial importance. As a competent bar peeling partner, Boehlerit offers end-to-end tool systems including peeling head, holder and cassettes.

Different geometries allow for optimum machining of the most varied steel qualities.

From the point of view of process engineering, bar peeling is a kinematically reversed longitudinal round turning where the work piece passes through a rotating tool, the peeling head. Bar peeling is in fact heavy-duty machining, economically done in a diameter range from 20 to 500 millimetres. The feed for standard materials is up to 18 millimetres today, which is several times the feed rate possible in general turning. Cutting depths of up to 15 millimetres are achieved with the proper cassette systems. If 600 to 800 rods of standard material, with a diameter of say 80 millimetres, are fed through a peeling machine in three to four hours – with cutting edge – this also perfectly illustrates the performance capacity of the indexable inserts used.

When it comes to bar-peeling, however, users tend to associate “heavy-duty” machining with “difficult” machining. The processes require enormous amounts of cooling lubricant and are not visible for the machine operator. And the high loads cause vibrations or guide problems. This is aggravated by the fact that often materials difficult to machine are used in the production of bright steel, such as stainless steels or alloys on nickel basis. Plus, forged rods, in particular, are often relatively crooked and not evenly round.

Process reliability depends to a great extent on the experience of the machine operator and on his sense of hearing. What is most important is to prevent the indexable inserts from breaking, which cause enormous damage to the cassettes, probably even the entire peeling head, the rod and the guiding rollers in the feed unit.

Cassette with indexable inserts e.g. triple peeling cassette

The only way to ensure optimum process management is the assessment of the machining result by means of dimensional stability and finish quality and an assessment of the chips, the wear of the indexable insert and the operator’s experience. The challenge lies in adjusting the process parame-ters and the application-specific tuning of the indexable inserts, which is in most cases done in close cooperation with the manufacturer of the indexable inserts taking the composition of cutting materials and geometries into account, such as length of cutting edge, chip geometry and supporting chamfer.

Always among the best

Based on its shared history with Böhler, a company that plays a leading role in the development and production of stainless steel, high-speed steel and tool steel at the highest quality levels, Boehlerit is always among the best in bar peeling when it comes to the machining of new materials. Boehlerit, an alliance partner of the LMT Group, also has all the coating technologies available within the group. Bar peelers profit from the comprehensive know-how from various applications and processes to achieve performance improvements through new layer developments. Due to the extremely high feeding rates and the character of the process, the biggest challenges lie in the required layer adhesion. The application-specific design of the cutting geometry plays a much more important role in bar peeling than in conventional turning. Boehlerit offers the widest range of geometries in standard versions, tailored to different classes of materials.

The Nanolock layer significantly increases productivity of bar peeling.

The development of a new type of indexable insert for the machining of duplex and/or superduplex steel is one of the current examples of innovative solutions for the machining of new materials and significant performance improvement in bar peeling. Another example would be the nanotechnology of the universal LC228E bar peeling grade.