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Who’s to blame when you can’t get conforming parts?

A group of us have had a long-running conversation on one of the social media sites about who's to blame when processors can't get conforming parts. Is it the part design? Is it the mold design? It is the molding process? And obviously there's always a lot of finger pointing in this game.

Jose Avellaneda, manufacturing manager at Plastics Plus Technology Inc., a custom injection molding company in Redlands, CA, commented, "I have witnessed the blame game in all areas of the molding process for the failure of a product. There are always difficulties when developing a process and the success of the product weighs heavily on the processor. In most cases, molds are not properly debugged or analyzed which cause unnecessary work or modifications. The processor must possess an expert knowledge of the injection molding machine and material being used in order to put together a process which combines temperature, pressure and time. The processor must also understand tooling to suggest where additional venting is needed or minor modifications required to remove the part from the mold. The craft of processing is rapidly disappearing in my opinion in this industry, and is greatly unappreciated. The molder can make or break a project if these tools do not exist. "

One member of the site commented that the question I posed on the PlasticsToday blog poll that appeared last month included several options but that there had been "limited response" to the question. "Is the lack of response an indication that we are all in denial? Perhaps," said this commenter. He added that he's going to stand by his opinion that a lot of problems come back to mold design, and in fact in many cases there's not enough forethought in the design stage in planning for the "inevitable - either those things that one will encounter in tool development or once the tool is released to production."

He then goes on to list several areas of consideration: proper splitting of the tool, inserting where it makes sense, lack of detailed drawings to name a few. "The detail drawings need to control not only the initial build but also the fabrication of future spares by anyone anywhere," he noted. "The drawings can leave no question about the tool's design intent. Our mutual success will always be in the details."

Randy Kerkstra, tooling manager at Royal Technologies responded, "The plastics industry is very interesting in the fact that you are learning something new almost every day. We all occasionally run across issues that are new and challenge us when trying to resolve them."

Kerkstra then went on to compare mold design vs. part design: "Part designs can be frustrating and create challenges. But assuming the bases have been covered - draft, nominal wall stock, rib-to-wall stock ratio, etc. - the mold design should be optimal. Mold design is very critical to success. The problem is not all mold designers understand this in depth."

Kerkstra told me in a phone interview that he spent the first half of his career as a moldmaker. Twelve years ago, he went over to the manufacturing side at Royal Technologies. "Before I went over to the manufacturing side I thought I knew how to build a good tool," he commented.  "Being on the manufacturing side now for 12 years has showed me I had no idea what a good tool was." 

"Processing is a very important tool to resolve issues, but every time you process around tooling issues your overall window becomes smaller," Kerkstra said. "I personally have been very successful with resolving issues by making the mold the focus. Venting, venting, venting. Good cooling and proper ejection. Those are the big issues. If you can modify the mold to resolve the issue your processing window stays large and better yet, focus on the tool design up front around the plastic being used. A robust tool equals a robust process."      

Craig Porter, president and owner of PlastiCert Inc., is so convinced of the importance of moldmakers understanding molding that he sends his moldmakers to "spend time in processing so they can see molds running and get a better appreciation for the challenges, and take real world issues into account."

PlastiCert provides mold design and build, and offers injection molding services as well.  "In the mold shop it's all about building the mold," Porter said in a phone interview. "Their goal is to make that mold and they don't often look at it from a molding standpoint or an operator situation. Working on the molding production side puts them in the shoes of the operators and the end user. The goal isn't just to make a good mold but making a good part as well, and keeping an eye on the end game. We have to provide quality parts to our customers and meet their pricing needs, which gets down to cycle time."

PlastiCert has four moldmakers and one mold designer in the tool shop. On the molding side, the company operates 10 presses from 30-440 tons, both horizontal and vertical machines, and specializes in two-shot and overmolding technologies.

Porter noted that having both operations under one roof puts Plasticert at a strategic advantage. "The moldmakers typically have a lot of communication with the molding side - but actually being on the production floor gives them a better appreciation for molding than just being there five or 10 minutes looking at a mold."

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