More reasons why injection molders fail at scientific molding

Falling dominoes

Last April, I presented 10 scenarios illustrating how companies that seemingly espouse scientific molding principles fail in their implementation. I could have mentioned many more, but to prevent putting readers to sleep, I got off my soapbox when I reached 10 reasons. In revisiting the article here, I have included some additional insights to the first 10 and added another five failures, bringing the total to 15.

Too many “medicine men” and not enough processors claim they practice the scientific molding ideology that John Bozzelli created, while others at the top of the industry have capitalized upon the use of the term. I personally remember sitting in a classroom the summer of 1993 as John taught his program. It changed my entire view on molding, and developed my approach toward true standardization. It gave me a sense of what validation truly means when, as molders, we establish process and develop controls. Beyond that, it defined the next 25 years of my career. I learned the importance of process development and recording. John’s insights have always steered me away from false readings, as well as defined my analysis of process.

It is important to understand what scientific molding is. It is not bells and whistles, with fancy terminology, beautiful pictures and fancy equipment that most plastics controllers are outfitted with nowadays. Outlining all the steps behind establishing true process would be its own article. But at the end of the day, scientific molding is a series of steps that first establish a solid repeatable process, which is then validated. True process is never the first step of the engineering phase. Process is developed following the stages of part design, tool design/building, material choice and press validation. Without these fundamental functions having been proven, process is limited to the failures attributed to these key functions.

Garrett MacKenzie, the author of this article, will present a free webinar on the key principles of scientific molding methodology on Feb. 13, 2018. He will address such essential topics as process development, recording, monitoring and control; standardization; design optimization experiments; and process optimization. Register now for this webinar. Busy that day? No problem: You can listen to the webinar on demand, but you must register first.

The general rule I use in validation is that if a process is true, a press meets or exceeds production requirements for a period of 24 hours with minimal (1.5%) to no scrap. This process must be repeatable and include a fully standardized setup. True processes are generally easy to start over and over with a minimal amount of startup scrap. In more complex cases, strict startup procedures are clearly documented and enforced to ensure that the procedures are sound and deviation is minimal. This means that the new job is easily changed over without variation and start up is achieved without a major scrap and/or process adjustment phase.

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