University of Twente Student Theses


Obtaining time reduction, in the movement of a clamp mechanism

Elshout, Tjeerd van den (2006) Obtaining time reduction, in the movement of a clamp mechanism.

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Abstract:The aim of this assignment was to check if time reduction of the movement of a clamp mechanism is possible. The clamp mechanism is the part of an injection molding machine, which keeps two mold halves together when the plastic is inserted. One of the mold halves is moved away with the clamp mechanism, to take the product out of the mold. Until the mold is closed, no new plastic is inserted. The faster the opening and closing movements of the mold are, the more products can be produced in the same time. A simulation model is made in 20-Sim, to analyze the dynamic behavior of the clamp mechanism. The model is made with standard 2-dimensional rigid-body models. The model is validated using measurements from the real clamp mechanism. By changing the friction coefficients the model is fitted to multiple measurements. The movement of the clamp mechanism depends mainly on the reference motion profile. If this profile is optimized, a faster cycle-time is achievable. With the knowledge about the clamp mechanism from the simulation model, a better controller can be realized. When feed forward is added in parallel to the PID-controller the reference profile is followed much better by the mechanism, since the required force to move the clamp mechanism can be estimated in advance. Because of that, the reference profile can be tuned for better results. During this assignment a simulation model is made, which is validated and fitted successfully with measurement data. The control system is expanded by implementing a feed forward controller, based on a reduced model. When the points where the deceleration is started are moved to a later position, the required safe velocities are still reached in time but the average velocity can be increased. Based on the simulation experiments, it can be assumed that the closing movement can be done 10% faster and the opening movement little more than 8%, if the feed forward controller and the cycle-tocycle method are implemented, and when the reference profile is optimized. It is recommended to do more tests using various mold weights, in order to validate the simulation model for more situations, which will make the model more reliable. It is suggested to implement the State Variable Filter for estimating the velocity, to obtain a more accurate derivative. It is recommended to model and analyze the hydraulic circuit, since this circuit has a large influence on the behavior. The clamp mechanism structure is rather common, but this transformation ratio has a large influence on the required force to move the mechanism. Further analysis is recommended to determine whether the lever mechanism can be improved.
Item Type:Essay (Master)
Faculty:EEMCS: Electrical Engineering, Mathematics and Computer Science
Subject:53 electrotechnology
Programme:Electrical Engineering MSc (60353)
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