Quality Magazine

Bottle Closure Capacity Increases With CMM

May 19, 2003
A full-inspection cycle that used to require an entire day now takes about 40 minutes to complete. Crown Cork and Seal Co. Inc. (Sandston, VA), a plastic bottle closure manufacturer, required a higher inspection speed to keep up with a doubling in demand for bottle caps from a major soft drink maker.

The company had been using a manual coordinate measuring machine (CMM) that was 15 years old and had a slow computer. "The need for a more productive CMM was clear," says Kelley Parkes, systems administrator at the Crown Cork and Seal plant. "Once we started getting faster production, we had to update the quality assurance as well."

The company chose Mitutoyo America Corp.'s (Aurora, IL) Bright Apex 916 computer numeric control CMM because of past experience with the company. The CMM has much greater speed, accuracy and degree of automation than the older system.

"It has tripled our inspection capacity and we will be able to deal with major future increases in the workload," says Parkes.

Linear motion on the Bright Apex 916 is four times faster than on the old CMM used by Crown Cork and Seal, while accuracy is also improved. The new CMM is capable of taking measurements down to 0.000001 inch. It runs virtually "hands off," which cuts inspection labor costs, Parkes says, and more closures can be checked. Before, samples were taken from only four injection molding machines at a time and tested every hour. Now samples are taken hourly from all the machines for testing.

Testing of a batch used to take 45 minutes, but now takes 10 minutes, while allowing inspectors to measure multiple parameters on each closure instead of one dimension per closure. Also, several closures can be measured at the same time, while before, only one type could be measured at a time.

The new CMM was fully operational within 2 weeks, and because the previous CMM was working in tandem, there wasn't a loss in production. "Because the new CMM is automated, we had zero downtime during the transition," Parkes observes.

According to Parkes, the new CMM is Windows NT-based with an interface similar to his home computer. An inspector chooses the three, four or five measurements that will check the inside and outside of the closures, and using a stationary aluminum fixture plate, the CMM then checks 196 closures at a time.

A full inspection cycle takes about 40 minutes. An operator requires about 10 minutes to obtain a full-shot sample from all 22 molding machines. Then 196 closures are placed on the measurement plate and indexed, which is a 20-minute procedure. The start button is pushed and the automatic cycle begins. "Manually it would take a worker an entire day just to do the same lot," says Parkes. "One worker can work on the new CMM, whereas the old CMM required the work of three operators," he adds.

The CMM, which was installed in 1998, "paid for itself within a year," says Parkes.

Mitutoyo America Corp.
(630) 820-9666
www.mitutoyo.com