The injection Cycle

Continuous production is achieved in elution chromatography by repetitive batch injection or cyclic batch elution. The injection cycle is timed so that the emergence of the last-eluted component of one batch at the column exit is immediately followed by the emergence of the first-eluted component to be collected from the next batch as shown, for example, in Figure 19.2b. At any one time there is more than one batch moving through the column. 

Cross-linking or vulcanizing a polymer to improve such properties as modulus, strength, thermal stability, etc. The 5-10 mm of resin in front of the screw tip that remains at the end of the injection cycle. It is used to maintain packing pressure on the melt until the cavity gate freezes. 

The mold then closes and the injection cycle starts again. 

Times for each of the cycle portions in Fig. 9-9 are relative. Optimum drying cycle time for the injection cycle is about 1.5 s. This drying cycle time includes opening of the molds, movement of the mold unit, and close time. Basically, plasticated polymer (after an injection delay) is injected into the mold (injection), where it is brought to holding pressure and conditioned. After the injection... 

One drawback, though, would be a little lengthening of the injection cycle. 

The molding process itself can have a large influence on the final properties of the part. The polymer chains undergo orientation in the flow direction during the mold-filling phase of the injection cycle as shown in Fig. 1.62. The amount of orientation in the final part depends on how much orientation was induced during filling minus the amount that was re-... 

Relatively slow since the injection cycle controls the machine s output. 

Fig. 19.35. Schematic of injection molding operation. A. When the mold starts to close, the screw has just finished charging the front end of the cylinder. B. With the mold closed, the heating cylinder then moves toward the sprue bushing and is ready to commence the injection cycle. C. The hydraulic cylinder then forces the screw forward under the injection head and fills the cavity. D. Cooling and charging cycle the mold is filled and, after the holding time, the screw starts to rotate and charge the front end of the cylinder. E. The screw is still charging the front end of the cylinder, and the cylinder starts to move away from the sprue bushing. F. The finished cycle the mold opens and the molded part is ejected with the sprue bushing. Du Bois, J. H., and John, F. W., Plastics, Reinhold, 1967 by permission of Van Nostrand Reinhoid Co.)...

An adaptive online predictive control technique was developed for controlling the non-linear dynamic behavior of the average part surface cavity temperature of a plastic part during the injection cycle using the coolant flow rate through the mold as the manipulated variable. 

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