How traditional injection molding processes create uncontrolled risk

Traditional methods of plastic injection molding rely on process development based on machine inputs. This means that an injection molder must trust that the settings they are entering on the machine are being reflected accurately in the actual process.

The problem with this informal method is that it often introduces uncontrolled risk in terms of the quality, timing and cost of plastic parts. To avoid these pitfalls, New Berlin Plastics uses a scientific injection molding process that monitors actuals (using sensors in the tool) rather than machine settings during production. This greatly reduces the risk that parts being produced don’t meet a customer’s specifications.

“Injection molding should be treated as a science, not an art,” explains Karl Held, Business Development Manager. “If a setup technician makes adjustments to the molding machine in-process to correct what he or she believes is an issue, it becomes an educated guess instead of a data-driven decision. This creates a situation where the setup technician may be treating a symptom rather than fixing the root cause that’s driving the issue. That increases the risk of inconsistent quality (and can result in creating new issues), which impacts the timing and cost of producing those parts. The waste created through these activities will eventually find its way to the customer.”

Here’s how a traditional injection molding process can have a negative impact on parts:

Quality issues

Parts developed using traditional injection molding practices are at higher risk of quality issues, especially non-dimensional problems that aren’t apparent during a visual inspection.

All molding machines and resins are inherently unique. That makes it almost impossible to get perfectly consistent parts every time without some variability. Sometimes these variables are slight and can be absorbed during the process. Other times, the variability has enough of an impact that it negatively affects part quality.

The best-case scenario is that the injection molder catches these problems during or after production and the issue never reaches the customer. But on occasion, bad parts make it to the OEM and can make it into their finished product. Once this happens, they may cause failures in the field, which can damage a company’s image and brand and can even lead to product liability exposure.

Cost issues

If a poorly-developed process is creating unnecessary scrap, that additional cost may find its way to the customer as a price increase. If high scrap and re-work costs are the norms, these tend to find their way back into a piece price to offset these conditions.

On the other hand, if an injection molder absorbs those costs internally, they’re creating a situation where their financial stability is being eroded. That may cause them to reduce critical activities such as reinvestment, which affects their performance long-term – or, in a worst-case scenario, the business may shut down or be sold. These events can cause major problems for customers’ supply chains.

Timing issues

Production problems can cause delays in part delivery, which can lead to unplanned downtime of an OEM’s manufacturing line. When bad parts are discovered by quality control, they require a time-consuming sorting process and/or another production run by the molder. These delays can be very costly to an OEM.

Driven by data

New Berlin Plastics eliminates these risks by using scientific injection molding processes, which give the company an average on-time delivery rate of 98%+. Along the entire production process, New Berlin Plastics monitors and prevents problems in multiple ways:

• Our systematic process development methodology uses data/information from experimentation, studies and calculations to drive the process of building a robust molding window that can absorb reasonable and inevitable movement in viscosity throughout the production run.
• Sensors in the molds are used to monitor actuals for things like temperature and pressure rather than relying on machine settings. In essence, this enables the process to be viewed from the perspective of the plastic resin, not the machine.
• The injection molding press and automation use this sensor data to identify when a suspected bad part is produced, automatically sorting it into a containment bin.
• Vision systems perform dimensional checks and automatically reject bad parts.
• Robotic de-gating systems automatically remove runners from parts for speed and consistency.
• A material characteristic library provides insights into optimal resin processing conditions.
• Comprehensive data records ensure the same process is followed for future production runs.

New Berlin Plastics is fully dedicated to the scientific injection molding process, so it provides customers with high-quality parts, on time and on budget. The company has found that data-driven decision-making is the way to guarantee happy OEMs.

“We want our customers to have peace of mind that we’re using many layers of quality monitoring to prevent bad parts from getting to them,” Held concludes. “Our goal is to be the supplier that our customers measure our competition against.”