An application solution from Kollmorgen
In web handling, velocity ripple causes uneven coating and unsightly horizontal bars across the substrate. There is one solution to overcome these challenges- perfect velocity control.
There are a number of factors that directly impact the ripple problem including Mechanical transmissions cause tooth or belt chatter, and each gear tooth or timing belt will cause a torque/velocity perturbation in the roll resulting in the “bar” effect, sometimes referred as banding. Machine mechanics, along with imperfections in the motor, feedback device, and drive control loop, combine to foil the notion of perfect velocity. Correcting for these variables will go along way toward achieving the desired velocity control. The motor’s primary contribution to velocity ripple is its electromagnetic cogging. which is usually at the pole or slot frequency or some multiple of it. The best way to overcome electromagnetic cogging is to begin with a low cogging motor that requires less correction. All standard Kollmorgen motors, including AKM, Direct Drive Rotary, (DDR) and Cartridge DDR are under 1% pk-pk cogging. They are superior due to electromagnetic design and simulation of the electromagnetic circuit.
Cartridge DDR or Frameless direct drive motors are the best weapon on the precision coating lines because they eliminate mechanical transmission, and with Cartridge DDR having the added advantage of being easy to implement. Read the whitepaper