Time control during injection molding

Distances can be controlled during injection molding. Control of distances is critical to producing high quality products at alow cost because longer distances result in longer cycle times. The most common distances are used for mold close, dosage or shot size, cushion or pad, screw return, mold open, and ejection. 

Control of the mold temperature is a key component for plastics quality. Table A.3 lists the typical mold temperatures for common plastics during injection molding (http //www.matweb.com/). The mold temperature can influence the quality of the plastic part. Warmer mold temperatures can help relieve stresses imposed on the plastic part during injection molding process and aid material flow of thin wall sections. The stresses imposed on the plastic part can cause warpage in the plastic part after it is removed from the mold. Cooler mold temperatures can help cool the plastic part faster and cause a reduction in cycle time. 

Fig. 13.36 The fractional coverage during nonisothermal gas-penetration experiments in PB-300, where the gas was injected after different F0 = at/R, that is, dimensionless delay times, following the step bath temperature switchover from 60° to 0°C. [Reprinted by permission from K. W. Koelling, V. Gauri, M. Tendulkar, R. Kaminski, and O. Becker, Understanding the Controlling Mechanisms of Gas-assisted Injection Molding through Visualization, SPE ANTEC Tech Papers, 43, 3697 (1997).]...

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