[Al Skierkiewicz]

My point is that the accuracy of the CIM motor is dependent on the brush spacing and the size of the brush assy. The CIM has approximately 6 distinct positions (steps) per rotation or 60 degrees +/- 90 degrees per step (based on the brush contacting two commutator segments +/- 1 segment). In a rough calculation using the above example of 100:1 reduction, the per step accuracy of the CIM would produce about 0.0004" +/- 0.0006" per step at the output of the lead screw or 0.1" +/-0.25" for 1 rotation of the lead screw, worse case. The 1.8 degree stepper as shown above will produce as described 0.0005" +/- 0.00002" per step or 0.1" +/-0.004" per rotation, worse case. While it is possible to produce better accuracy in the CIM in a closed loop configuration and with higher reduction ratios, there is a diminishing return on investment. This example does not take into account the accuracy of angular position within a 100:1 transmission and assumes it to be infinitely accurate.