Delta MMC120 User Manual download pdf (Page 68)

Troubleshooting MMC120 Linear Motion Control Module

68 Delta Computer Systems, Inc. 360/254-8688

The System is unresponsive and hard to tune

This problem could have several causes. The first items to check are:

1) Is there hose, rather than rigid pipe, installed between the hydraulic valve and the cylinder? The hose acts

like an accumulator and the fluid goes to fill the hose rather than move the cylinder.

2) Does the valve have overlap? Overlap in hydraulic valves causes a significant dead band and slows the

system response. Some proportional valve amplifier cards have dead band eliminator circuits which make

tuning easier.

3) If you have a servo motor and a ball screw, is there any backlash? Backlash produces a dead band when

the axis changes direction, so the controller will tend to oscillate around the dead band.

The axis oscillates

This problem could have several causes. The first items to check are:

1) Make sure that the DEAD BAND ELIMINATOR value is not too high.

2) Try reducing the PROPORTIONAL, INTEGRAL, or DIFFERENTIAL gains.

The axis does not finish moves or moves differently than expected

This can be caused by the PLC issuing unintended commands to the module. Use the DCS120 command

queue to monitor commands sent by the PLC to the module. Confirm that only the expected commands are

being sent. See Appendix A: DCS120 Diagnostic and Setup Program for more information about the

command queue.

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Delta MMC120 User Manual Page 68