This is the test setup of the z axis. I have a 20 inch diameter cardboard circle mounted on the top shaft of the z stepper. It has a line from the center to the edge. We have a thin metal pointer mounted to the machine frame. The pointer is .010 inches thick and on edge in relation to the circle mark. The z axis only has 2 inches of total movement so the testing will be done with 1.5 inch movements. The circle is mounted to the shaft with a hub and setscrew. The z axis is set up for a 1/2 x 16 acme thread, 25600 pulses/inch, 30 inches/min.,accel is set to 5 and step and dir pulse width to 5 micro seconds

test 1: Whith pointer aligned and z in down position and zeroed the MDI was used to move Z up 1.5 Inches.
result: The mark on the circle is past the pointer by .06 inches on the circumference of the circle. It went to far.
Using the MDI to move back to zero the mark on the circle is .100 inches short of the pointer.

After running these tests numerus times and reseting the pointer each time the results are not very consistant. Some times the results can vary by as much as .050 - .060 inches. The width of 1 pulse on the edge of the circle is .0393 inches. The edge is marked in .100 inch increments using a caliper. So the test distances are eyeball amounts.