Bob,
Still addressing the 4th axis defined as being angular.
For motor tuning you calculated the steps per value, and then used the calibration feature.
Now lets go back to motor tuning again. Be aware of what the grahics is showing in the motor tuning window.
The graph shows how the stepper will ramp up in time ( accelerate), run at at some velocity, then ramp down. Change the velocity or acceleration and be aware of what the graphics is telling you. With a 25k Kernal speed the graph will only change so far ie; you can only get so manny pulses to drive the motor.
At some velocity, acceleration, or combination of both the motor will skip.
Practicaly speaking you can't go from a standstill and accel instantantly. For a stepper as the motor rpm increases the torque decreases, so, you need to limit the max velocity so there is adequate torque for machining. Speed can come once reliability is assured. Depending on what you are machining will determine how "you" limit the velocity.
You should know what your max velocity and accel is.
At a combination of max velocity and accel you can check the rpm. The rpm at any lower velocity value can be found quickly by just succesively dividing the max velocity found ( ie; find rpm using a stop watch for one revolution ( 360 degrees) at max velocity). Max rpm/2 is rpm of the lower velocity if it was cut in half. Note that the total time to rotate 360 degrees is influenced by the acceleration. Looking at the graphics can show time required for the ramps.
You can do a lot of hand calcs, but, there is an easier way:
STEPS PER UNIT CALCULATOR - members docs
http://www.machsupport.com/forum/index.php/topic,16315.msg110286.html#msg110286This spread sheet will calculate the required steps per unit for linear and rotary stepper motors.
Imperial and metric calculation are provided for. Pulses per second are also calculated based on miscellaneous inputs.
StepperCalc_ALENZ_rev1.xls
Play with the calculator for different values.
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Before we do some gcode commands for the rotary you need to be aware of the current state of the machine.
Different gcodes are shown in the upper right corner of the screen and they will change depending on an
an entered gcode command.
SO
Print the Gcode Reference which can be found in Using Mach3 Mill Manual - Page 10-12 Figure10.4
There are few others commands not listed but the list will serve you well.
Then compare the codes listed on the screen to the list. After a while you'll know what to look for.
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To be continued,
RICH