Mold Temperature Regulators

WatchDog, Mold temperature regulator, Burger Engineering... 

The initial molding temperature regulates the interdiffusion of polystyrene molecules between pellets. Pellets molded at the lower temperatures simply have insufficient time to interdiffuse, and do not, therefore, lose pellet shape "memory" caused by chain entanglements. Tn has been ascribed to whole chain motion by Boyer and as such should be the temperature above... 

Heat effects on the film during impregnation with Cl are chiefly aimed at optimizing the temperature regimes of the film material molding, and regulating heat exchange and physical-chemical transformations in the hose-inhibitor contact. 

The mold for thermoplastics receives the molten plastic in its cavity and cools it to solidity to the point of ejection. The most is provided with cooling channels. The mold temperature is controlled by regulating the temperature of the cooling fluid and its rate of flow through the channels. Proper cooling or coolant circulation is essential for uniform repetitive mold cycling. 

Figure 5.23 Phases of operation of HR system temperature regulator with microprocessor a - soft start - heating c - operation d - break in operation Reproduced with permission from Mold-Masters)...

While the flow behavior of the melt is regulated by the temperature rise, the same sensor measures the cavity temperature before the arrival of the melt. This information can be used to adjust different mold temperatures by automatically controlling the different cooling circuits of a mold. Identical cavity temperatures are required for large molded parts for an optimal shrinkage behavior of the parts. 

The dynamics of the molding process are determined through control of different but related machine elements such as motors, heaters, servovalves, etc. These machine elements are typically controlled via a hierarchical closed loop control architecture as shown in Fig. At the innermost level, only the machine elements are regulated by real time comparison of the desired machine set points with the machine feedback, such that the difference (or error) is used to correct the process. At the second level, state variables such as melt temperature and melt pressure are controlled to track prespecified profiles and provide more precise control of the state of the melt. At the outermost level, the machine inputs are adjusted by the machine operator to improve the quality of the part through specification of better set points given feedback of part quality. 

Bonner, J.T., Clarke, W.W.J., Neely, C.L.J. and Shfkin, M.K. (1950). The orientation to light and the extremely sensitive orientation to temperature gradients in the sHme mold Dictyostelium discoideum. J. Cell. Comp. Physiol. 36, 149-158. Chang, C., Kwok, S.F., Bleecker, A.B. and Meyerowitz, E.M. (1993). Arabidopsis ethylene-response gene ETRl similarity of product to two-component regulators. Science 262, 539—544. 

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