One of the biggest trends in manufacturing is automating inspection with robots, driven by falling robot costs, a tight labor market, and the push to inspect 100% of critical dimensions. Air gaging fits that world well.
More than a go/no-go check
Air gaging is no longer just a go/no-go gage. It's used in fully automated stations for 100% inspection, with feedback to the machine tool for offsets. The plugs and rings haven't changed much except for getting smaller; the big advances are in the readouts, often called comparators, columns or measuring computers. They offer digital and analog I/O, Ethernet, fieldbus, USB and RS232, so the gage can run semi- or fully automatically, including mastering.
A typical automated cycle
Mastering
Mastering can be manual or automatic. In an automated cell, the MIN and MAX masters are usually made in the form of the workpiece, so the robot can load them the same way it loads parts. The MIN master is loaded and mastering is started by a button or by the PLC through digital I/O; it ends on a stop signal or a timed countdown. Then the MAX master is loaded and the cycle repeats. Mastering can be triggered by a timer, a part count or manually. Once per shift is typical, though some customers master more or less often.
Measuring
The robot loads the part and signals the start. The measurement ends on a countdown or a signal from the PLC, and the readout reports good or bad so the robot can sort the part. The readout can also send offsets to the machine, usually based on at least a three-piece average, so adjustments happen without anyone touching the machine. Full SPC runs in the background and can be exported.
Scaling up
A cell can check one diameter or run several stations for many features. The most we've measured on a single station is just over 200 features, and the capability is much higher. We've also integrated serial-number tracking from data matrix codes on the part, so each part's measurements are stored and can be recalled at any time. Air gaging in these cells measures far more than diameters: perpendicularity, taper, parallelism, runout and flatness, among others.
What it costs
With robots and measuring systems both coming down in cost, a simple automated air gaging cell costs less than many people expect. It runs around the clock, so payback can be short. For examples, see our automated station with a Fanuc robot and crankshaft gaging projects, or read about the air-to-electronic modules that connect air gages to PLCs.