CMT Field Notes: 2014 Thin Gauge Thermoforming Workshop

Penn College of Technology, Williamsport, PA

As we mentioned in our previous post, the 5th Annual Hands-On Thin Gauge Thermoforming Seminar was a sold out event. With participants from all over the country, the classroom and labs were packed for all three days. CMT was involved again this year by supplying HYTAC FLXT and XTL for the 12-cavity mold that is used on the single-station MAAC machine in the thermoforming lab.

The workshop offered a balance between theory and practice, classroom learning and laboratory testing. In addition to running plastic sheet in the MAAC, participants also ran a small extruder and then analyzed data in the testing labs. Testing procedures included Gardner Impact, Flexural Modulus and cutting force studies.

Mark Strachan of uVu Technologies and Dr. James Throne were the primary instructors. Professors Kirk Cantor and Joseph LeBlanc from Penn College also presented. The topics ranged from the molecular structure of polymers to the physics of heating plastic sheet to the calculations required for trim force in steel rule die cutting. Dr. Throne in particular provided extremely granular analysis on the science of thermoforming, including some mind-bending equations to explain the rate of recrystallization in polypropylene. The important takeaway was that PP contines to recrystallize long after the part has been formed, trimmed, stacked, packed and shipped to the final customer. The use of nucleants (such as Millad 8000) serves to increase the rate of crystallization while adding clarity to the extruded sheet.

In the thermoforming lab, participants were challenged to improve the wall thickness of parts formed from 0.040″ (1.01mm) white HIPS sheet. With a limited number of levers to use, the group changed the temperature settings and the vacuum delay and compared results. Temperatures ranged from 285F (140C) to 315F (157C) and vacuum delay changed from 2.9 to 4 seconds. Even though plug speed and forming pressure were fixed, there were very clear changes in material distribution from one sample to the next. The 12-up tool contained 9 XTL plug asists with the same geometry and 3 FLXT plugs with different radii. While wall thickness measurements were not completed for every cavity, visual inspection suggested distinctly different types of material flow as evidenced by thick corners and thin walls across the mold.

Penn_College_tests

The PIRC put together an excellent program that included a river cruise on the Susquehanna River and a catered lunch at the school’s own culinary institute, Le Jeune Chef. Participants had ample networking time as people from resin suppliers, sheet extruders, thermoformers and tooling materials companies all contributed to a rich discussion throughout the workshop.  In the near future, a thin-gauge thermoforming machine will be brought into the program to allow for improved training.

Given that this year was a complete sell-out, it is advisable to book your spot early next year!

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