Hypertherm Phoenix 8.0 - Manual (Page 451)

Motion Overview
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Systematically increase the Velocity Gain until it has little or no effect on the following
error or until instability becomes noticeable. Proportional Gain would then be used to
increase the “stiffness” of response. Integral Gain can be used to improve the steady state
performance. Derivative Gain may then be used to provide a dampening effect.
After tuning for the best response, increase Feed Forward Gain systematically to further
reduce following error if necessary. It is not required that you eliminate following error
but it is wise to ensure that Following Error for each axis is similar. Please Note: Feed
Forward Gain will reduce steady state following error, but may cause overshoot.
It is important to note that some following error is desirable, following error terms should
be nearly the same from one axis to another, and the polarity of the following error term
must be the same as the direction of travel.
Finally, check the system tuning by placing a pen on the system. “Draw” the test pattern
provided in the simple shape library and observe the cornering capability, arc/ circle
contouring and the ability to position at the center crossings. When troubleshooting
tuning issues, varying the size and trial speed can often provide valuable information
through observations of the pen tracing.
After the system has been successfully tuned, adjust the Servo Error Tolerance to equal
twice the normal Following Error for the axes (note: This is a common approach to
setting the Servo Error Tolerance but is up to the discretion of the service agent) . This is
allows the system to operate without nuisance faults caused by temporary resistance to
the motion, such as dirt on motion rails or temporary tension from motor cabling, etc.