Concepts of In-Process Measurement and Control
The concept of in-process measurement and control has to do with measuring a process variable while that variable can be influenced and applying a corrective feedback to the machine that affects the process so as to encompass the sources of error that normally occur during the process and thus eliminate error from the variable on the resultant workpiece. However, changes in American manufacturing are allowing many of the in-process measurement goals to be attained. The measurement of the actual dimension can then be compared with the size mandated by the part blueprint and, finally, the machine can be adjusted accordingly to bring the dimension into the proper range. The solution depends on the type of process being controlled, the type of measurement being made, and the rate of change of the process variables. Although this text deals primarily with measurement and control applied directly to a measurement on machine, the measurement sensor need not be mounted on the machine.