Hello Robert,
Does the error occur on a particular type of measurement; shoulder, circle. etc? If the error is feature dependent, it might be tip/tip comp related. If it is not feature dependent, it may be a counting problem. The reader signal conductors are of a very small gauge. Because these cables are constantly flexing when you move the axes, the conductors can open intermittently. Unlike a DCC machine, the closed loop systems of a manual machine are limited. In a DCC machine, if a reader cable was open, the system would know because it issued a command for motion and no count was forthcoming. In the case of a manual machine, if there was no count while the operator was moving the machine, the system would assume that the operator stopped moving the machine. Only under very narrow circumstances will a manual machine generate a counting error. If you are experiencing 8-88 or 8-89 or 8-90's then it is almost definitely a counting problem. If you are not experiencing these errors, it may still be a counting problem. You may be able to set up a test for loss of count signals in one or more of the axes. First, home your machine in -x,-y,+z. Try to make note of exactly where you homed the machine. Then move the ram to the extreme +x,+y,-z of the machine. Again make note of physical position. Jot these coordinates down (in MAC). When the feature problem occurs, return to MAC coordinates and reposition the ram to the physical extremes which you previously defined. If there is a significant difference, the problem is probably dropped counting signals.

Regards

Dave Fitch
Axis Metrology,Inc.