Rotary cutters are used to to cut material to length at constant speed, a process often referred to as 'converting' which can include other pre-processes such as 'slitting'. This cutting method can be used for a variety of materials including paper, film and some thin sheet metals. The rotation of the cutter is typically one revolution for a given cut length. Some custom solutions for short lengths could theoretically have more than one blade per revolution. Blades of twin rollers are synchronised or mechanically linked and are sometimes used to cut material in a scissor action from one side to the other as they rotate. Blades which cut in a scissor action often requires a feature for mechanical compensation to ensure a parallel cut with different speeds, which can also be easily automated.
Principle
In the animation above a rotary knife or shear, is used to cut the material at the registration mark. The basic relationship is one revolution of the cutter for the length of material. The motion is essentially electronically geared together. The blade motion has to be synchronous to the material speed during the cut itself to ensure a clean cut. This requirement means that the rotational speed for the remainder of the rotation has to compensate, either running slower or faster to ensure the blade reaches the start of the next cut precisely.
Motion can be achieved using CAM functions which can be mathematically more complex than necessary. Mint FLY commands provide a simple means of achieving the motion shown above by gearing motion with fixed acceleration of a master (material) distance. They can even be used to create S-ramped motion (not shown above).
Registration
The registration mark is detected using one of the fast position latch inputs (drive or motion controller depending on the products used) and the relative position (angle of the cutter is captured and resulting error calculated. Compensation can be applied by altering the effective gear ratio over the remaining cutter rotation or using the MINT OFFSET command
Alternative solutions from ABB
In addition to Mint solutions which can be programmable drives or NextMove based, ABB can also offer high power ACMS1 drives (up to 355kW) with function block programming and AC500 PLC with iEC61131 and PLCopen with choice of fieldbus.
Alternative products for IEC6113 programming:
ACSM1 high power motion drives with SPC programming
AC500 PLC for IEC61131 based solutions with EtherCAT or ProfiNet
Features used:
Auxiliary encoder for material synchronisation
High speed position latch to accurately measure product position
Built in software flying shear (flying knife) for position synchronization or software gearing using FOLLOW with a position offset using OFFSET
