Plug Material vs. Plug Geometry: A Thermofoming Test
It’s one of our favorite thermoforming questions: “Which is more important – the plug material or the plug geometry?” It’s really a trick question, though, because the answer is usually, “It depends!” So let’s take a look at a recent test we did with 2 types of HYTAC plug assist where multiple variables were involved.
Motivation for the test:
The cups in question have a plug mark at 20mm from the bottom of the cup. After changing the plug geometry and plug material (from XTL to FLX) there was a better result. It was not clear if that was because of the different type of material or because of the different shape of the plug.
General details:
Machine: tilt-mold, cut-in-place
Part: Ø70,5mm (2.77″)
Material: White PP 1,05mm (0.041″)
Machine oven temperature: 408°C / (766°F) (top and bottom)
Sheet temperature: ± 150°C (302°F)
Test procedure:
The test was run with 4 different types of plugs in the same row of the tool.
- Hytac XTL: Small Radius (R 4.0) Angle 4.0° (Cavity 5)
- Hytac FLX: Small Radius (R 4.0) Angle 4.0° (Cavity 3)
- Hytac XTL: Large Radius (R 8.0) Angle 5.0° (Cavity 2)
- Hytac FLX: Large Radius (R 8.0) Angle 5.0° (Cavity 4)
Results:
The machine was cycled for about 3 minutes with cups measured from the same shot.
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Hytac XTL: Small Radius (R 4.0) Angle 4.0° (Cavity 5)
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There is a plug mark at 20mm from the bottom of the cup.
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Enough material in the bottom; bottom thickness is good.
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Hytac FLX: Small Radius (R 4.0) Angle 4.0° (Cavity 3)
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There is a plug mark at 20mm from the bottom of the cup.
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Less material in the bottom; bottom thickness is acceptable.
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Hytac XTL: Large Radius (R 8.0) Angle 5.0° (Cavity 2)
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There is no line at the bottom of the product.
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Enough material in the bottom; bottom thickness is good.
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Hytac FLX: Large Radius (R 8.0) Angle 5.0° (Cavity 4)
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There is no line at the bottom of the product.
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Less material in the bottom; bottom thickness is acceptable.
Conclusion & Discussion:
- The plug with the small radius (R 4.0) creates a plug mark at ±20mm from the bottom of the product.
- Hytac XTL carries more material to the bottom compared to Hytac FLX.
- Plug No. 3, Hytac XTL with Radius= R 8.0, gives the best result in this test.