As highlighted by Plastics Today in the article “The Troubleshooter: Preventing Flash in Injection Molded Parts,” the landscape of plastic injection processing has transformed from an art to a science over the last 30 years. Esteemed pioneers like John Bozzelli, Don Paulson, and RJG have equipped processors with tools to validate plastics processing and provided methodologies for utilizing historical data to identify changes within established process systems.
In the inaugural piece of “The Troubleshooter” series, the focus is on offering insights and solutions for various defect scenarios in plastic injection processing. Concentrating on flash, a prevalent defect in plastics, the goal is to achieve zero trimming by operators, reducing inspection time and minimizing the risk of poorly trimmed parts reaching customers. The longer a mold runs with a flash condition, the more costly the mold repair becomes during servicing.
The article emphasizes that different types of flash indicate specific issues, such as feather-like flash pointing to a high-heat condition, thick flash caused by overpacking, low tonnage, or mold damage. When flashing conditions persist across multiple molds, it’s crucial to verify platen parallelism to meet press manufacturer requirements.
It stresses the importance of identifying the root cause of a flash condition before making any process changes. This involves cleaning the mold thoroughly to eliminate the possibility of a dirty mold causing flash conditions. Simultaneously, operators must inspect the die for flash build-up and check for any flashed or damaged moving slides or components.
Verification of the process is the next step, checking for any recent changes in setpoints such as barrel/mold temperature, tonnage, shot size, cut-off, injection speed, pack/hold, and back pressure. Additionally, reviewing the material is crucial, ensuring the correct material is used, with consistency in material lots and regrind percentages within established limits.
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