Cycle Speed in Thermoforming

How do we increase productivity via cycle speed while at the same time improving part quality? To know how this works, you must first understand the basics in thermoform ing.

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Film is cycled through the machine. With each cycle, the foil (sheet) is heated by the main heating tunnel with upper and lower heating zones to the desired sheet temperature.

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But with each cycle, the heated film stops in front of the cooled tool. The cooled tool has natural radiation and cools down the hot sheet. The slower the machine runs, the more the sheet cools down in front of the tool. This makes it more difficult to form the sheet because it is losing heat. This leads to poor material distribu tion: eventually you might find holes in the formed cup.

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With a higher cycle speed, the cold tool has less influence on the heated foil. This means that with a higher cycle speed, the sheet cools down less: the result is a warmer sheet. This is easier to deform. Better material distribution.

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When the foil temperature is 140°( (284°F) in front of the mold, you will form a good cup. lf the cycle speed is slow, the sheet temperature must be much higher because the cold tool cools down the sheet. lf the cycles speed is low, the foil is partially overheated in order to form the cup. Most cups are brittle when the cycles speed is low because the material has been destroyed.

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With a higher cycle speed, the sheet does not have tobe heated as much, so there is less stress on the films. And the cups are stable and tough.

With every increase in cycle speed, you will encounter new problems. These are so-called bottlenecks. Bottleneck_s have to be solved step by step in order to be able to in crease the cycle speed step by step.

15 cycles per minute 4 seconds lnfluence of the cold tool on the hot sheet 20 cycles per minute 3 seconds lnfluence of the cold tool on the hot sheet 30 cycles per minute 2 seconds lnfluence of the cold tool on the hot sheet 40 cycles per minute 1,5 seconds lnfluence of the cold tool on the hot sheet 50 cycles per minute 1,2 seconds lnfluence of the cold tool on the hot sheet