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The choice of sensor is dictated by the size and shape of the part. Furthermore, the type of process has to be taken into account, with the properties of the material affecting the mold cavity pressure. This necessitates a special sensor design for plastics. The size of direct sensors chosen is determined by the front diameter. To simplify sensor installation and to allow measurement with higher sensitivity, the largest possible sensor front must be chosen. Direct measurement is very reliable and preferred to other installations. Molds with a complex design or whose cavity wall may not be machined can be equipped with indirect sensors. These are also chosen according to size in order to suit the ejector plate. When using indirect sensors it is also important to take into account the force acting onto the sensor through the ejector pin. Contactless sensors measure the strain of the mold steel; therefore the cavity wall need not be changed. The corresponding mold cavity pressure can be derived from the measured strain and used for monitoring. Contact temperature measurement uses temperature sensors or combined pressure and temperature sensors. The latter ensure an easier insatllation and allow pressure and temperature monitoring at one and the same point in the cavity. The following table gives an overview of the sensor types supplied by Kistler.
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