Case Studies: The Flexible SPC Advantage
Thermoformed packaging components roll off the production lines by the thousands at Portage Plastics Corp. (PPC, Portage, WI). From instant cereal bowls to clamshell packaging for windshield wiper blades to containers for baby wipes, the variety in sizes and shapes of containers the company can produce is mind-boggling. For its largest customers, the production volume can total millions of units per year.
Flange width, part depth and thickness are the most critical dimensions affecting finished parts at PPC, so the company relies on Synergy 2000 statistical process control (SPC) software developed by Zontec Inc. (Cincinnati). The software allows PPC to collect part measurement data and monitor process variation, signaling when process adjustments or corrective actions are needed on its production lines.
The software is used within the quality assurance lab at PPC headquarters in Portage, WI, and networked to a satellite manufacturing facility in Brownsville, TX. It provides feedback that helps PPC improve machine use, eliminate wasted materials and meet customer requirements. Measurements are automatically entered into the software using calipers and digital indicators, eliminating manual data entry and improving input accuracy.
Industry-Independent AnalyticsCustomers across the food, automotive, electronics, medical, personal care, agriculture, hardware and consumer industries expect PPC to consistently meet their packaging applications and performance criteria. “Because every customer’s job is unique, I needed a program that would help me analyze the data in numerous ways regardless of the differences in our customers’ processes,” says Heidi Beaver, PPC’s certified quality technician.
The thermoforming process begins as plastic rollstock is fed into a series of ovens. The material is then conveyed to the forming area where vacuum is applied. The PPC in-line operation allows for much shorter cycle times than other thermoforming processes. Female molds are typically used on in-line machines because spacing between mold cavities can be minimized to reduce the amount of trim scrap and recyclable material that is generated. The “plug assist” technique optimizes wall thickness and provides greater detail for intricate parts. After parts are formed, vacuum and air release them from the molds and initiate the cooling process. Steel rule or matched metal die options are available for trimming depending on the shape of the finished package.
A comprehensive selection of SPC charts allows PPC to see drifts in the process that might otherwise be missed by merely looking at spreadsheet data. “If we see trends we don’t like, I can take data from several different production runs and overlay them onto one control chart or run chart to make quick visual comparisons,” notes Beaver.
Better Process AnalysisThe software has enhanced the company’s ability to pinpoint and react to adverse events that occur during production, such as oven or heating issues, ambient temperature changes, material issues, trim press vibration, equipment maintenance issues and over-adjustments to machines.
“The versatility in the query function gives me the exact data I need at any given time,” says Beaver. “Previously, I just looked at a 48- cavity tool as the entire process: six rows across and eight deep. Now I look at the process by individual rows because we can get more performance differences with the outside rows than we do from the inside rows. Therefore, I can immediately determine that my biggest shrink factor is affecting the outside rows, or know we have heating issues if we get thin sidewalls.”
PPC also uses the software to help with production part approval process (PPAP) recordkeeping, product traceability and change management logs for their automotive customers.
“Our engineers are absolutely sold on the system. Understanding how our processes work is definitely leading to better problem solving and higher parts-per-million quality,” says Beaver.
“The biggest advantage from our SPC program is the ability to assess process capability,” says Quality Manager Paul Bauer. “It provides us with the data to make process improvements one product at a time.” As an example, PPC saved $21,000 by monitoring just one key quality characteristic on a high-volume product during the course of a year.
Integrating Quality and ProductionFifteen hundred miles away at the Brownsville plant, PPC has trained operators to take their own part measurements and enter the data directly into the software during second and third shifts. That location is staffed with a quality technician on duty for the day shift only, so real-time, networked SPC has moved the quality function closer to the point of production and helps hold the line on headcount.
At the same time, the Wisconsin facility gets immediate access to the data and notification of what is occurring remotely. Beaver says the benefits of integrating data collection into the production function has such merit that the company’s strategic direction is to train not only quality technicians and operators on the system, but supervisors as well, and expand the concept across both locations.