Machining in-process gage calibration from reference master

A system for grinding workpieces to preselected size comprising

• grinding means including a wheelslide having a grinding wheel mounted thereon and means coupled to said wheelslide for advancing said wheel into grinding engagement with a workpiece,
• gage means including a gage having a pair of caliper arms and an output which varies with position of said arms, and means for positioning said gage with said arms in engagement with a workpiece so as to provide a said output indicative of workpiece size,
• a gage master having a predetermined fixed size relative to said preselected size, said positioning and advancing means being operable during a first mode of operation to position said gage arm in engagement with said gage master, and during said second mode of operation to position said gage arm in engagement with a workpiece and to advance said wheel into grinding engagement with the workpiece,
• compensation circuit means coupled to said gage means and comprising first reference means for establishing a reference signal indicative of said predetermined fixed size of said gage master, and means coupled to said gage means and to said first reference circuit means and operable during said first mode of operation to provide a compensation signal which varies as a function of a difference between said gage output and said reference signal, and
• means coupled to said gage means, to said compensation circuit means and to said advancing means to control operation of said advancing means during said second mode of operation as a combined function of said gage output and said compensation signal.

In a machining operation wherein engagement of a machine tool with a workpiece is controlled in real time by a workpiece measurement signal from a gage likewise engaged with the workpiece, a method of calibrating said workpiece measurement signal for variations due to gage wear, temperature and the like comprising the steps of:

• (a) providing a gage master having predetermined master dimensions relative to desired machined size of said workpiece,
• (b) periodically bringing said gage into measuring engagement with said gage master to provide a gage master measurement signal,
• (c) providing a compensation signal as a function of a difference between said gage master measurement signal and said predetermined master dimensions, and
• (d) thereafter controlling operation of said machine tool as a combined function of said workpiece measurement signal and said compensation signal.