Mitsubishi Electric WS0-CPU0 - Function blocks for press cycle control

Chapter 9
237
Logic programming – Function blocks
BDC and Overrun cam monitoring
If BDC and Overrun cam are enabled, the BDC input signals must accord with Figure
223 and the following rules.
(1) The beginning of the BDC (Low-High transition) must be close to 180° and has to
occur while the TDC input is High and after the falling edge (High-Low transition) of
the Overrun cam input (the Overrun cam input may have changed back to High
already).
(2) The end of the BDC (High-Low transition) has to occur before the falling edge
(High-Low transition) of the Overrun cam input. In other words, BDC must be Low
when a High-Low transition at the Overrun cam input occurs.
A valid sequence that fulfills the conditions for BDC and Overrun cam is:
1. Start condition: TDC = Low, BDC = Low, Overrun cam = High
2. TDC: Low  High
3. Drive released = High (this is to fulfill the condition for overrun monitoring)
4. Overrun cam: High  Low
5. BDC: Low  High
6. Overrun cam: Low  High
7. TDC: High  Low and BDC: High  Low (sequence does not matter)
Depending on the type of press (e.g. hydraulic press), it may occur that the beginning
of the BDC (step 5 above) occurs not once but twice or even not at all. To avoid that
this leads to a contact error, the parameter Number of BDC signals per cycle must
be set to the value 0-2 (e.g. hydraulic press). With this setting, the conditions for the
BDC still apply for every BDC pulse with the exception of the falling edge of the
Overrun cam input (step 4 above).
Figure 223:
Contact monitoring with the
Universal press contact
function block with BDC
enabled