Alongside high process security and a high machining speed, perfect bar surface quality and geometrical accuracy are the most important criteria for our customers in the bar peeling industry. An important prerequisite for the above requirements is the choice of the peeling machine. Different machining methods and combinations of cutting inserts in SINGLE, TANDEM or TRIO cartridge systems entail varying levels of power consumption on the part of the peeling machine. The formula below serves to provide a rough calculation of the required drive power P [kW], which can be used to determine the number of usable cutting edges/indexable inserts:
vc = Cutting speed (m/min)
ap = Cutting depth (mm)
f = Feed per cartridge (mm/rev)
Kc1.1 = Specific cutting force (N/mm2)
Note that this rough calculation of drive power only applies to one cartridge system. If a peeling machine is equipped with one peeling head with 4 cartridges/tool slides, the drive power calculated using the formula must be multiplied by a factor of 4. With regard to the cutting depth ap, note that the individual radial cutting depths of all roughing and finishing inserts are added up for a TANDEM or TRIO system.
Both feed and cutting depth have the most significant impact on productivity. However, these are restricted by the abilities and maintenance condition of the peeling machine and its peeling tools, as well as the condition of the raw material, which generate unavoidable vibrations. Ultimately, reducing vibrations in the peeling process is the key to success when it comes to productivity and product quality.
Depending on the quality and hardness of the material to be processed, the tailored finish of the support chamfer provides additional support in the peeling process in terms of process stability. The nominal value of this support chamfer angle influences whether the finishing insert arranged in parallel in the axial direction between the bar and support chamfer forms a clearance angle (positive inserts), establishes positive contact with the bar (neutral conditions), or exerts enormous pressure on the bar material (negative inserts). Different materials require indexable inserts with tailored, supportive properties. The support chamfer angle and length of the secondary cutting edge ultimately influence the quality of the bar surface produced, and also, importantly, the choice of the right indexable insert for the existing cutting depth ap. Chip breakers specially adapted to the properties of the material break the chip generated during the peeling process into a usable length.
The cutting depth plays an important role here. As described in previous chapters, there are indexable inserts for bar peeling that are suitable for rough machining, medium machining and finish machining. The designations of CERATIZIT chip breakers already indicate the application area, the depth of cut ap. Chip breaker designations with the letter "R" (rough) should be used for depths of cut larger than 3.0 mm, those with the letter "M" (medium) for depths of cut between 1.0 and 3.0 mm, and those with the letter "F" (fine) for depths of cut smaller than 1.0 mm – these are always suitable for finishing. The best possible machining property is achieved based on this selection, cutting forces are optimally introduced into the indexable insert and maximum tool life is reached. When designing TANDEM cartridge systems, the majority of the depth of cut should be executed by the roughing insert; the depth of cut of the finishing insert should be between 0.5 and 1.8 mm depending on the type of finishing insert.