| 摘要 |
Automatic thickness profiling for use in blown film and other extrusion line s. The automatic system is integrated into an air cooling ring device either external (24) and/or internal (30) to the bubble or extrusion (22). It comprises one or more high resolution circumferentially variable annular air outlets (62) which act to cool the molten resin in a circumferentially variable way. Thin slide plates (72) remain fixed in place except when adjusted to open or close the local annular air outlet by the action of at least one scanning actuator (99). The actuator is positioned by control signals generated by a control computer (106) which calculates the appropria te local dimension of the variable air outlet in response to circumferential position correlated with thickness variations detected by a film thickness sensor (102). The film thickness above the frost line is mechanically scanne d around the extrusion. In the case of making blown products with internal cooling, counteracting adjustments are made as local flow areas of the internal cooling device are changed to maintain constant the entrapped air volume. The novel actuation system is also shown to be useful in locally adjusting a finely segmented air lip. A method of correlating thickness changes with respective cooling zones is also disclosed.
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