Yaskawa MotionWorks+ Windows Software - Manual (Page 227)

MotionWorks+™ Appendix C MW+ Camming 101
221
The slave offset is also useful when the machine cycle is not an integer. Imagine a
machine where a timing belt is used as shown:
Every time the knife rotates, 0.2 pulses required to keep the knife orientated in the correct
position are lost. This error will add up quickly, and after about 11,000 cycles, the knife
will be off by 45 degrees.
A remedy to solve this is to count the machine cycles, and use the SLAVE OFFSET block
to add back the lost pulses. After 100 cycles, the knife will be behind by 20 pulses. Using
the SLAVE OFFSET block will correct the physical error of the knife, but numerically, the
knife’s position will still seem to be drifting.
Imagine a clock, but the machine cycle cannot be set to exactly 12, the closest you can set
it is 11. The line in the clock indicates the position where the machine cycle numerically
indicates 12 O’Clock (or 00:00 hours military time.)
The slave offset can move the pointer ahead one hour each time and keep the physical
position correct. Notice that if you want to position the pointer at the machine’s 12
O’Clock position after it has run 5 cycles, you would actually have to position it to 5
O’Clock. Keeping track of the total SLAVE OFFSET added (total of all relative offsets
given) is the key to keeping the position under control.
Rotary
Knife
22 teeth
Motor
20 teeth
8192 pulses 9011.2 pulses
12
6
3 9
12
6
3 9
12
6
3 9
12
6
3 9
12
6
3 9
12
6
3 9
1 2 3 4 5