Measuring Clamping Force and Mold Protection
Modern injection molding machines are equipped both with mold protection and clamping force measurement. Mold protection is activated while the mold is being moved, and actively protects the mold against damage. In this phase the forces must be measured using a high-resolution, fast sensor to enable the machine to respond sufficiently quickly to any foreign body (for example a part that is not ejected) that is on the separation plane.
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Clamping force is measured after the two halves of the mold make contact during the closing movement; this data is used to control clamping force.
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The forces that occur as the mold is being moved are typically smaller than the clamping forces by a factor of between 20 and 40. The simplest way of measuring the force is to measure the surface strain. The surface strains that occur when subject to specific forces depend on the rigidity of the structure.
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The measurement itself can be made at different places on the clamping unit, for example on the toggle or on the end-plate of the clamping unit. The strains that occur on the toggle are usually greater than those on the end-plate. The new strain transmitter Type 9238AQ... enables all the various ways of measuring clamping force/mold protection to be covered using just a single transmitter.
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This transmitter contains the sensor and associated electronic components in an extremely robust case. A serial interface allows the transmitter to be configured for different measuring ranges, and can therefore be installed either on the toggle or the end-plate, using two measuring ranges to measure both the small forces during mold movement and the high clamping forces. Both signals are available in parallel on the two outputs. Additional options such as Live-Zero and Signal-Offset can be set as required. Kistler supplies the sensors pre-configured to customer specification.
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Quality Molding is the 100% quality seal for injection molding processes.
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Quality Monitoring and Process Control for Injection Molding Processes Download PDF
Kistler and STASA develop an automatic method for the prognosis of injection molded part quality
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