Metal Cutting Corporation (Cedar Grove, NJ) is the largest independent source for burr-free abrasive wheel cut-off metal parts. Their principal business is the cutting, grinding, lapping and polishing of small diameter metal tubes, wires, and rods to extremely precise dimensions and with surface finishes as smooth as one microinch. Their products are used in the medical device, automotive, electronic, electrical, computer, and semiconductor industries.

About six years ago, a major automotive manufacturer approached Metal Cutting Corp. with a problem that no one else had been able to solve. Metal Cutting Corp. had already done some work for this company, which recognized MCC as a unique organization able to create parts that no other company could. However, the problem presented by the customer was challenging even for MCC: To attain the performance the customer needed from the fuel injectors, MCC had to demonstrate the ability to check tolerances for fuel injector components down to one micron and sort them at a rate of up to 70,000 per day. Since MCC was the sole source for this part, it was essential to meet the customer's additional requirements.

MCC took the problem to their metrologist, an expert on measurement. The metrologist was not optimistic about measuring the parts to such a low tolerance by automated methods. But measuring 70,000 parts per day by manual methods was out of the question. The Engineering Manager at Metal Cutting Corp. consulted Control Technology Corp., and together they came up with a solution: a Height Sorter machine that not only measures, sorts, and bags up to 70,000 parts per day to the customer's tolerances, but also sends the information to a database on a PC. This enables the customer to review the data at any time and has helped MCC to attain ISO 9002 and QS-9000 certification. A CTC rack style automation controller that has two stepper modules, an I/O module, and a serial communications module controls the Height Sorter. Five Height Sorters are linked to a PC via a small network.

The Height Sorter receives the fuel injectors in the top of the machine, and a vibratory hopper feeds each ring-shaped injector component down a tube into a measuring area. A laser-based measuring device measures the deviation of each part from the nominal one millimeter thickness, and relays the information to the CTC controller, which then calculates the part's size. The CTC controller moves a chute to one of seven positions based on the part's size. Five positions are for parts of various dimensional categories that are graduated in five-micron increments, one is for oversized parts, and one is for undersized parts. After measurement, each part is pushed down the chute and drops into the appropriate bag for parts of that size. After 1200 parts have gone into a given bag, the CTC controller stops the machine and sends a message to the PC, which tells the operator the bag is full and needs to be replaced. A printer attached to the PC prints out a barcoded label that gives the customer information on lot number, part size, and a date/time stamp for the parts. The operator removes the bag, affixes the label, and prepares it for shipment to the customer. CTC keeps track of the counts and measurements of each piece for all bags, ensuring that exactly 1200 parts go into each bag. This system ensures that the customer receives the expected number of parts, without any of the "giveaway" associated with conventional package-by-weight techniques.

In the six years that the machines have been running, the MCC engineer reports that two of the chutes on the machine have always remained empty: the ones for parts that are out of spec, and would therefore have to be rejected. In fact, Metal Cutting Corp. has run an estimated 75 million parts through the five machines, working 8-16 hours per day, five days a week, with no downtime, no rejected parts, and no trouble. "Reliability, not cost, was the driving concern for this project," says the MCC engineer. After consulting with a colleague who was already using CTC controllers, the MCC engineercited CTC equipment's dependability as the primary reason for designing it into the Height Sorter. CTC has lived up to the MCC engineer's expectations: "The CTC is the heart of this system, and we've never had any trouble with it," he says. All five machines are connected to one personal computer running a Visual Basic application, which prints the barcode labels, tracks sizes and converts alarms from the CTC controller into operator advisories.

Metal Cutting Corp. is so pleased with the performance of the machine powered by the Control Technology Corp. controller that it is looking to provide consulting services to other companies that require equipment that sorts parts to low tolerances. As MCC builds its consulting business, CTC will be at the top of its list of suppliers.