Hello Joe,
Your WM280V lathe uses a DC permanent magnet motor. This type
of motor along with the typical speed controller provided has very
poor linearity in the low speed range. The response that you see to
the test function built into the PMDX-107 reflects that. The best way
to cope with that is to adjust for the expected speed at 100% in
test mode and then use the Linearity.dat table in Mach3 to make
corrections for the lower speed ranges. While Mach3 can collect
this data automatically, I usually recommend measuring the motor
response and entering the data manually. At speeds above about
30% of rated speed you should achieve reasonable success.
Verification of maximum speed and data collection at other speeds
must be done without a Linearity.DAT file present in your Mach3 folder
in order to get unadulterated data.
To confirm proper operation of the PMDX-107 you can measure the
output voltage of the PMDX-107 between the Aout and Agnd terminals.
The voltage there will be a percentage of the voltage applied to the
Aref and Agnd terminals. At full speed the voltage on Aout should
be close to the same a the voltage on Aref. At 50% of full speed
the voltage on Aout should be close to half of the voltage on Aref.
These measurements should be taken using the built in test mode
or from Mach3 WITHOUT a Linearity.DAT table present in Mach3 as
the linearity correction will change them.
There are two other concerns in your configuration that you did not
mention.
First, you must have your Pulleys configured in Mach3 in order for
the S word settings to be meaningful. Mach3 uses this information
to compute the percentages for PWM by determining the ratio of
requested speed to the maximum possible for the pulley in use.
Second, the SmoothStepper has an unusual requirement in that it
needs an acceleration setting even though the spindle is not an axis.
Please see our application notes about using the PMDX-107 with a
SmoothStepper here:
http://www.pmdx.com/Doc/AN002_PWMSpindleSmoothStepper_02.pdfSteve Stallings
www.PMDX.com