Plastics Technology

OCT 2018

Plastics Technology - Dedicated to improving Plastics Processing.

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coolant flow by installing flow meters within the cooling circuits. Another option is to monitor mold surface temperature. Ideally, we monitor both coolant flow and mold temperature. Molders and their customers are becoming increasingly data oriented. This business strategy aligns well with utilizing Systematic Molding principles. When you complete studies on machines and molds, you'll be equipped with the information needed to build robust decoupled processes. The data drives our processing, thus creating greater transparency between companies, customers, and co-workers. As you make changes, you can defend them with data. Letting data drive your processing decisions also makes troubleshooting so much easier. This is how we systemati- cally tackled our burn issue in the disc mold mentioned earlier. Using decoupled processing, the first thing we did was look at "fill-only parts" by removing second-stage time and pressure. The fill-only parts had no indication of burn. The burn was observed at the end of fill only when we packed the parts. We then decided to remove second stage (pack and hold) again and adjust our short shot so that the part was fuller before tran- sitioning to second stage. As we progressively filled the part out further, we noticed the burn was returning. With this information, we decided to put a sticky note at the top of the mold at the parting line. Putting the sticky note between the mold halves at the parting line allows the air to properly vent from the cavities (effective, but not recommended). When we did that, the burn went away. This was the final piece of information we needed to isolate the cause of the burn issue. The vents in the mold were not at the proper depth to let air escape from the cavity during fill. To eliminate the burn, we added a second fill speed that was significantly slower than the first speed. This allowed the air to escape before transitioning into pack and hold. After just 20 min of gathering and examining data, we accom- plished two things: 1) We were able to determine the cause of the burn; and 2) We found a way to mold the part without burn. Some might call it witchcraft, and others claim we were plain lucky. But neither is true. Though there are many causes for part defects, decoupling a process makes it faster and easier to systematically diagnose their root causes and identify possible solutions. By decoupling your processes, you can separate defects by whether they are related to fill or to pressure. Some part defects that commonly relate back to the fill stage would be splay, jetting and burn. On the other hand, warp, sinks, voids and bubbles are more commonly related to pack and hold stages. Establishing machine and process baselines as well as learning to interpret data do not happen overnight. These things take time, and what works for one molder is not necessarily going to work for another. What you can do is continue to learn from each other's experiences and trust what your data tells you. Ultimately, continue to apply systematic molding principles because they work to improve processes and, ultimately, profits. ABOUT THE AUTHOR: Logan Teut is a qualified Train the Trainer and Master Molder I, specializing in machine maintenance, grinding/ blending, mold maintenance, scientific molding, and Decoupled Molding. As a consultant/trainer for RJG Inc., Traverse City, Mich., his responsibilities include teaching Injection Molding Essentials, Systematic Molding, Decoupled Molding Workshops, Successful Strategies for Tool Launches, and Master Molder I in the Midwest. Contact: 231-947-3111;; Underwater Pelletizers Production rate up to 79,000 lbs/hr Strand Pelletizers Production rate up to 44,000 lbs/hr NEW to the Maag family — Continuous Melt Filtration Throughputs to 12,000 lbs/hr Piston & Side Plate Screen Changers Throughputs up to 100,000 lbs/hr x 6 class extrex ® Gear Pump Throughputs up to 33,000 lbs/hr PUMPS, FILTRATION & PELLETIZING SYSTEMS for extrusion, compounding & recycling | +1 800.622.4872 reduction pulverizing systems gala automatik underwater pelletizers automatik scheer strand pelletizers maag pump & filtration systems Letting data drive your processing decisions makes troubleshooting so much easier. 50 OCTOBER 2018 Plastics Technology FE ATURE

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