Originally Published MPMN
Originally Published MPMN September 2003
PROFILEContract Manufacturer Helps OEM Meet Surging Demand for Trocar Sleeves
High-speed molding machines and automation put a company back on track
Acombination of low-speed injection molding machines and manually operated pad printers was slowing down a company's production of trocar sleeves and affecting product quality. Unable to meet market demands, the Fortune 100 company contacted
Classic Industries Inc. (Latrobe, PA; www.classicplastics.com). The job came with two demands: the full-service contract manufacturer would have to enhance productivity and increase product quality. Process improvements and innovative engineering enabled the firm to not only boost production twofold and improve quality, but to help the OEM reduce costs. In addition, the
customer did not need to invest in new molds.
Trocars are complex surgical tools that form a tunnel through which instruments such as laparoscopes can be inserted. The thin-walled trocar sleeve relies on a series of external, circumferential barbs for stability. Classic's team examined the trocar mold and resin selection, and conducted a mold-flow analysis of the part. The main obstacle the team had to overcome was injecting polycarbonate into a multicavity mold to make a 5-in.-long part with a wall thickness of 0.020 to 0.030 in. without flash.
"Standard molding machines do not have enough pump volume to fill the parts in a consistent fashion from shot to shot," says Spencer Siegel, vice president for market development for Classic Industries. The solution was to rework the existing molds and use high-pressure molding machines. According to Bill Larrimer, Classic's vice president of engineering, "the injection time to fill a sleeve with these machines is less than 1¼10 second, and the process is consistent and stable."
The key objective involved increasing production of quality parts using the existing molds. "We looked at the project with our customer to determine not only the immediate goals, but what was anticipated in the future," says Siegel. "To achieve this goal, we automated the process in a variety of ways."
The use of process monitors was one element. These devices continually monitor the molding process to ensure that all parameters remain within set control limits. If one of the parameters such as the heater band, injection speed, or hold pressure goes out of the limits, the part is automatically diverted to a separate bin.
Automating the pad printing line also improved process efficiency. Prior to Classic's involvement, the customer was using manual pad printers. "We converted that to an automated operation," says Siegel. "A vibratory bowl feeds parts into the pad printer automatically, loads them onto the spindle, and at the end of the process removes them," he adds. Automating the printing sped up the process and also reduced rejects.
"Classic has been successful because we work with the customer to find solutions and make them successful," claims Larrimer. "We continually look for ways to increase performance and reduce total manufacturing costs for all our customers." By reworking the molds and automating the molding and printing processes, the OEM can produce nearly 7 million trocar sleeves a year. "Now our customer is in an [excess] inventory situation," says Siegel.
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