| 摘要 |
An electrical control system produces signals to control the movement of the mandrel in the centre of an extruder die so as to regulate the wall thickness of a thermoplastic parison for blow moulding. The system has an input fed with a number of target values for the wall thickness which are interrogated as the material is extruded and produce signals for a regulator which adjusts the position of the mandrel; another input adjusts the gap between mandrel and extruder head and produces a signal corresponding to the gap. An adding device adds the signal for a base gap to that fed to the regulator; a third input adjusts a factor and a computer multiplies the target values fed to the first input by the adjusted factor. The first input has a memory for the values fed in; its output leads to a first (basic gap) calculator which produces an entity for the basic gap from those values; the output is connected to a second factor calculator which provides an antity corresponding to the factor from the max. and min. values from the memory; the output is also connected to a third target value calculator, which itself is connected to the second input and output from the first calculator; when a basic gap is reset this third calculator adds the new value to the difference between the earlier target values and value for the basic gap. The output of the memory is connected to a fourth (target value) calculator; this is connected to the outputs of the first and second calculators and the third input; when a factor is reset this calculator multiplies the difference between the original target values and basic gap and the quotient of the new and old factors, and it adds the original basic gap value to the results and write the sums as new values into the memory.
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