Intrapac Sees 20/20

April 1, 2004
Machine Vision System Ensures 100% Integrity of Teflon Coating Process
The operation is simple enough in concept: Coat the inside of a metered-dose inhalant (MDI) canister with Teflon so that the medicine won't adhere to or react with the canister's metal walls. Miss a can, though, and the intended dosage could be affected.

"If an uncoated can were to go out, it could potentially affect a person's health," explains Jim Bunyard, program manager for the Intrapac unit in Harrisonburg, Va., that performs this procedure on three different sized cans at a line speed of 182 per minute (200,00 per day) for a major pharmaceutical company. "A 100 percent inspection rate is critical," he says.

The coating procedure line is a high-production, continuous line that operates 24 hours/day from Monday through Friday. Uncoated cans arrive in a bulk package and are then put into a hopper that lays them down and feeds them into a chute. From there, they are fed into an oven where they are annealed to clean off moisture. The canisters then go into a coating unit where six coating guns coat every other can, so that each can is sprayed by three guns. The coated cans then go from the conveyer to a bake oven and from there to an accumulator which collects the cans and puts them on an inspection conveyer.

A video system had been used to perform inspections in the past, but the outdated system had recently begun to fail. So Bunyard and technician Rick Moyer were charged with finding a new system that could ensure the required 100% inspection rate. "The technology was very old," Bunyard says. "The software was no longer available, so we decided to do the research to find a replacement system. I knew machine vision existed but I knew nothing at all about it," he says.

They evaluated a number of machine vision system suppliers, but in the end settled on Duluth, Ga.-based DVT--- in part because of the company's product reputation, but primarily for its service and support. "We were impressed with the fact that DVT provided extensive training, software updates and online diagnostic support at no charge," he says.

Fresh from their DVT training, Bunyard and Moyer realized that successful resolution of this inspection challenge would hinge on lighting. Indeed, the presence or absence of the coating in question can scarcely be determined by the human eye. Working with Advanced Illumination (Rochester, Vt.), the company evaluated an alternative LED ring light with an optical lens, but, ultimately, was able to use the original light ring and optical lens for its lighting, Bunyard says.

To accomplish the inspection, the camera first must identify the position of the can by finding the outside rim, then peer into the half-inch diameter hole of the can. The camera looks down at the bottom of the can to detect the presence or absence of the coating. At the same time, the rim of the can is lighted so the camera can inspect roundness. The vision system also ensures that no slivers of raw material are on the can.

"We perform eight functions to carry out these inspections within milliseconds, because every can is considered to be rejected until camera functions tell the PLC that the can positively passes all inspection criteria," Bunyard says. "This is a fail-safe setup, to assure that all cans are acceptable, even if there could be a system failure."

To overcome glare in the center of the bottom of the can, the DVT Framework circle line intensity tool was the perfect answer for the inspection, Bunyard adds. Using the Framework emulator tool, the entire integration was much easier, he says. "It took only two days to install and validate because we had already performed the tough work offline using the emulator," he said. "The emulator helped us tremendously."

To meet stringent 21 CFR Part 11 compliance validation procedures, six uncoated cans were fed through the system every 30 minutes to see if the vision system would detect and reject the faulty cans. "We didn't miss a single can. It rejected them every time," Bunyard says.

They now do six faulty cans per shift and, according to Bunyard, the camera never misses. "We are very happy with the DVT system" he adds, "and are currently looking at taking it plant-wide."

Inside Intrapac

IntraPac manufactures of a full range of metal and laminate tubes along with complementary closures, including tamper-evident designs.

Six years ago, the company introduced metered-dose inhaler (MDI) coating technology to the global pharmaceutical market. MDI coatings are applied to metered-dose aerosol cans used with prescription grade medication for asthma. A special Teflon coating is sprayed and cured in heat-sterilized containers preventing the product from adhering to the inner wall of the dispenser, a necessity for inhalers using ozone-friendly propellants.

The 280,000 square-foot IntraPac plant in Harrisonburg, Va., (formerly CCL) is more than 40 years old and employs 400 people. The Harrisonburg facility is one of four IntraPac business units in the U.S. and Costa Rica.