Monitoring machine-independent variables ensures consistent part quality

It’s an OEM’s worst nightmare: a bad batch of parts brings the assembly line to a standstill, causing expensive downtime and delaying the delivery of finished products and sales. With the complexity of raw plastic materials and multiple variables in the molding process, there’s always a possibility that out-of-spec plastic parts can make it through a molder’s standard quality control methods and onto an OEM’s production floor.

Fortunately, it’s possible to significantly reduce the risk of bad part quality by monitoring machine-independent variables (MIVs) during part development and production. New Berlin Plastics implements this technology as a standard process for producing consistently high-quality parts – and assuring the peace of mind of its OEM customers.

Early detection

Measuring MIVs is part of a scientific process to proactively monitor product outputs as they are being made instead of waiting until the product is molded and cooled. This allows engineers to get ahead of problems and make adjustments before bad parts are produced.

“Relying on just machine settings can have surprisingly different results in part quality due to the large number of machine-independent variables,” explains Technical Operations Manager Eric Pipkin. “Even two molding machines of the same make, model and year with the same settings can produce parts with subtle differences.”

Traditional quality control methods rely on inspecting parts after a batch has been molded and cooled. That means thousands of parts may be produced over several days before they’re even identified as out-of-spec. While this means that initial production happens very fast, it can have a detrimental impact on quality and ultimately slow down the final product delivery.

Beyond machine settings

MIVs are related to the raw polymer’s characteristics and the production environment, such as the polymer’s molecular weight and moisture level, percentage of fillers (such as reground plastic and glass fiber) and the production facility’s ambient temperature and moisture levels. Differences in one or more of these variables can impact part quality.

To measure these variables, New Berlin Plastics engineers embed sensors into several key locations within the mold. They measure and analyze the plastic continually during production and monitor changes that threaten to impact quality. These variables include:

• Plastic viscosity and flow
• Mold cavity pressures on the polymer
• Moisture levels
• Fill times
• Part weight and dimensions (before and after cooling)

Data-driven development

During part development, New Berlin Plastics design engineers look for potential problem areas and determine the best locations for the sensors in the mold. They measure MIVs and establish ideal variable value ranges with tight tolerances for the best consistency. That data is put into a template specific to that part and stored in an eDART data acquisition system.

Once production begins, engineers continually monitor and analyze this data to ensure problems are addressed immediately. Historic data allows engineers to look at trends, which is valuable for making future production changes.

The New Berlin Plastics difference

While the technology to measure machine-independent variables is not new, New Berlin Plastics has evolved its use to a higher level to optimize risk avoidance for all its customers.

“In-mold sensing and data analysis is standard practice in production for all products, not just on select projects or development,” Pipkin emphasizes. “Plus, we have allocated internal resources to evaluate the data and make appropriate decisions to improve part quality. It’s a valuable troubleshooting tool so we can validate processes and solve problems quickly.”

The adoption of in-mold sensing is part of a larger scientific molding culture within New Berlin Plastics that relies on data to determine best practices and manufacturing processes. All employees involved in these processes are well educated on how to use the technology, which dramatically reduces the risk of a customer receiving bad parts.

“We give customers a high level of assurance by using a robust method of detecting problems as they happen, not after the fact,” Pipkin adds. “It gives them peace of mind to know we will contain and fix a problem before it leaves our facility.”

These processes allow New Berlin Plastics to maintain very low levels of scrap and keep rework costs down. By keeping these costs low, they don’t find their way back into a customer’s part price. This allows New Berlin Plastics to offer a high level of value at a competitive price while protecting our financial security by not absorbing unnecessary costs.

To anyone considering a new contract molding partner, Pipkin has this advice on how to evaluate whether the MIV measurement process is fully integrated into a molder’s culture:

“Visit their facility and ask to see a demonstration of production with in-mold sensing and data measurement in action,” he recommends. “Ask how the data is used once it’s gathered, and whether employees are trained to use it. Information that just sits in a database is not valuable to anyone.”