Detroit — Extrusion and polymer processing expert Mark Spalding won the Research/Engineering Technology Award at Antec 2019, but instead of talking polymer molecules, he stressed the importance of knowing the fundamentals.
And that was the title of his speech at the Society of Plastics Engineers' conference in Detroit: "Process Design and Troubleshooting Using a Fundamental Approach." Spalding, a veteran of Dow Chemical Co., is a fellow in packaging and specialty plastics research.
"A key to successful projects, as I see it, you need to have great mentors. You need to have great team members. And I've been blessed with both," Spalding said. "My management has also allowed me to understand the fundamentals of the process, along with trying to diagnose, trying to fix something."
Spalding, a chemical engineer, worked on the early 3D simulation of single-screw extrusion at Dow in the late 1980s.
"Since its development, there have been more than 1,000 designs and troubleshooting projects that have been performed for Dow customers," he said.
He discussed issues with film extrusion as the keynote speech on a session on single-screw extrusion of sheet.
"A defect-free product, especially for polyethylene film, needs to be gel-free, especially if you're going to sell this into a premium-grade market," Spalding said.
Gel formation is a problem.
"Gels are common in most extruded film products for polyethylene, and it's really due to either an improper shutdown or it's also poor screw designs. But these can mitigated or eliminated by getting rid of the stagnant regions within the screw channel," Spalding said. "And it's not hard to do if you know what to look for or you appreciate what's happening."
The extrusion expert outlined how to calculate flow issues and do troubleshooting. One problem, called flow surging, is a rapid change in the pressure and output of the extruder even while it runs constant setpoint conditions. Spalding said that can be caused by a screw that gets too hot.
In other words, understand the fundamentals.