SCN 3575 was a change to leave the lag active during die return. Turning the lag off was causing a motor jump.

Having the lag off makes the die return smoother at the expense of a motor jump as the die comes to a stop at the end of travel.

The lag calculations rely on a filter for the command velocity. That filter adds a phase shift in the calculated command velocity. Suddenly removing the lag portion of the analog, which relies on the command velocity filter, results in an abrupt change in analog voltage or velocity command for SERCOS.

SAMCO complained about this, the only solution was to leave the lag active all the time.

This same phase shift is also responsible for the knee "velocity overshoot" that can be seen in the closed loop data screen. The phase shift results in the die position being behind because we are under correcting for the die velocity due to the phase shift. The overshoot is the die having to catch up to the target as the phase shifted velocity catches up to the actual velocity. This phase shift causes a knee or velocity overshoot at each trapezoid transition in the set point motion profile.

SAMCO is now complaining about vibration that can be seen at the transition points when the die stops at end of travel and at home. This new parameter allows them to turn off the lag during the die return, which will make the transitions smoother, returning the motion profile to what they are used to.

The harsh transitions are more impactful on them because they are using belt drives that stretch, which results in vibration.