Tech Talk
What is “In-Process Gaging”?
Cylindrical grinding is a very precise and highly productive machining process. Large batch production of parts on a cylindrical grinding machine requires in-process gaging. Across a series of manual operations, there can be a great deal of movement of the part in and out of the machine for measurement. Each relocation of the part increases error, and as final size is approached, the grinding becomes ever more tedious as the operator attempts to achieve the required service finish and the exact diameter at the same time.
In-process gaging allows the part to be very accurately measured while it remains in the machine. Modern cylindrical grinding machines have the in-process gage tied into the CNC control system, so that the entire grinding cycle is automated. The machine effectively inspects itself and the parts are consistently ground to size.
The in-process gaging system operates by two styli touching the workpiece periphery. The position of the styli are fed back to the control system, which then positions the grinding wheel with respect to the diameter of the workpiece. Such systems can also very accurately measure interrupted diameters, like splined shafts, by an adjustment of the damping in the styli fingers. Further sophistication is the ability to measure to a shoulder, thus combining the measurement of the diameter with its position along the shaft. A CNC grinding machine, in combination with “Flag” gaging and in-process measurement, can locate a part’s position, perform a series of diameter and step grinds relative to that flag location, inspect all aspects of diameter and land widths within very close tolerances, consistently and fully automatically.
