Essentially, bar peeling constitutes a heavy-duty machining process that is usually applied to diameters ranging from 20 to 500 millimetres. With standard materials, feed rates of up to 18 millimetres per turn are achieved today, a rate that is many times higher than that achieved with general turning. Using appropriate cartridge systems, cutting depths of up to 15 millimetres are realised. Turnaround times of 600 to 800 bars with an 80-millimetre diameter made of standard materials also bear witness to the performance capacity of the used indexable inserts.
But bar peeling is also a heavy-duty process in terms of difficulty. The processes take place using enormous amounts of cooling lubricants, which means that they are not visible to the machine operator. At the same time, tools and machines are put under an enormous amount of pressure. In the long run, this may lead to vibration or stability problems. Another aggravating factor is that cold finishing often utilises materials that are difficult to machine, such as stainless steels or nickel-base alloys, and that forged bars in particular are often quite warped and unsymmetrical.
To a large extent, process reliability is down to the experience of the machine operator and his sense of hearing. The breaking of indexable inserts in particular must be prevented, as this would cause enormous damage to the cartridges and possibly also the shaving head and the guide rollers in the insert apparatus.
Optimum processing is really only possible by assessing the process results, the dimensional accuracy and the achieved surface quality. Experienced operators will also know how to assess the chipping and the wear and tear of the indexable insert. The adaptation of process parameters and the fine-tuning of the inserts are usually performed in close cooperation with the insert manufacturer and through the composition of the cutting material and geometries, i.e. length of the cutting edge, chip-breaking geometries and design of the supporting chamfers.
