Auto OEM Grinds 8,000 Parts Per Hour To +/-2 Microns

A new industrial controller that Royal Master Grinders, Inc. is integrating with its high-precision centerless grinders, is helping a Big 3 automaker turn out precision parts at 8,000 per hour. The custom-configured Series 832 industrial gaging controller, from Mahr Federal, Inc., (Providence, Rhode Island) interfaces with Allen Bradley PLCs to provide real-time control over the grinder's regulating wheel, and hold manufacturing tolerances to under 4 microns (0.0015").

This impressive capability is the result of a joint development project entered into between Royal Master and a Big 3 automaker, to design a new control system for Royal's well-known TG-12×4 high accuracy centerless grinder. The project's immediate objective was to allow the auto OEM to grind fuel injector bodies at a rate of 8,000 per hour, while maintaining total tolerances of ±2 microns, including a roundness tolerance under 0.25 microns, and a comparably demanding specification for straightness. Of course, fully automatic operation was required to attain the desired rate of throughput, including automatic parts loading and unloading. Royal Master has extensive experience in integrating material handling systems, but needed assistance on the control system.

Royal Master contacted Mahr Federal, Inc., which agreed to supply its Series 832 industrial gaging controller in the form of discrete, panel-mounted components. Royal integrated these components with Allen Bradley Panel View 550 control systems in a single enclosure. Mahr Federal had previously only supplied the Series 832 in the form of benchtop gaging systems, or pre-installed in NEMA enclosures. "Federal was very cooperative in changing the format of the production for our application," said Robert Reyes, Royal Master's electrical engineer on the project.

Federal's custom engineering work did not stop there. The application required that the gaging amplifier/controller be able to switch between two input channels on command from the A-B PLCs, via the amplifier/controller's RS-232 port. Within a month of learning of the requirement, Federal Products reprogrammed the Series 832 EPROMs to meet Royal Master's need. "Engineering assistance from Federal was excellent," said Mr. Reyes.

The Series 832 controller helps the TG-12×4 perform both infeed and throughfeed grinding. In infeed mode, an LVDT gage head acting against the ram bed, provides input to the 832 controller, which constantly monitors the position of the regulating wheel, in-process. Meanwhile, communication between the PLC and Royal Master's Compumotor indexer/driver tells the machine when to rapid grind, when to switch to creep feed, and when to stop.

In throughfeed mode, the Series 832 controller is used post-process to compensate the machine for wear on the grinding wheel. The operator takes a finished part and places it in an anvil-type gaging micrometer mounted next to the grinder. An electronic gage head opposite the micrometer head measures deviation from the part specification, and with the push of a button on the Panel View 550 keypad, the operator downloads the compensation value from the controller to the PLC. The Series 832 then confirms, via the ram bed gage head, that the appropriate compensation has taken place.

The Series 832 controller features six measurements ranges, digital resolution to 10 microinches or 0.00010 mm, and switchable inch/metric units. The system can be configured to accept one or two contact-type electronic gage heads from several manufacturers, air gaging, and non-contact capacitance probes. Noise and environmental immunity is provided by a pressurized NEMA enclosure. A panel-mount version is now available on a non-custom basis. The system is being used in pre-, in-, and post-process applications by manufacturers of bearings, print rolls, spool valves, and other automotive applications.

"We have worked with Federal for many years on various special projects," said John Memmelaar, Jr., Royal Master's director of marketing and MIS. "Their salespeople aren't just reps: they're technically very knowledgeable, and very helpful from an applications point of view." Mr Memmelaar says that the TG-12×4 project was a complete success. The automobile OEM for whom the product was developed is successfully meeting his production and quality goals, and Royal Master has sold several of the machines equipped with Federal Products' Series 832 industrial gaging controllers.