Document Type and Number:
Japanese Patent JPS5311023
Kind Code:
B2
Abstract:
An injection molding control to promote uniformity in the mass of the injection charge from cycle to cycle. An injection ram is reciprocated between a fixed forward, or cushion, point coincident with the end of charge injection, and an adjustable rearward, or retraction, point correlated to size of the next charge. The retraction point is corrected at the conclusion of each injection cycle in response to comparing a reference pressure, which is correlated to the mold cavity pressure existing at the conclusion of injecting a charge of the desired mass into the molding cavity, with the pressure of the plasticized material upstream of the orifice through which the material is injected into the mold cavity. The material pressure upstream of the orifice is sampled for comparison against the reference pressure at a point in time following injection when the ram has a predetermined velocity, preferably when it has come to rest, and the injected material in the region of the orifice has not yet solidified, whereby the sampled melt pressure is correlated to the cavity pressure at the conclusion of injection and hence to the mass of the injection charge. Depending upon whether the sampled melt pressure upstream of the orifice is above or below the reference pressure, the retraction point is shifted closer to, or further from, the orifice, respectively, to shorten or extend, respectively, the distance over which plasticized material for the next charge is accumulated forward of the ram tip.
Application Number:
JP11672673A
Publication Date:
April 18, 1978
Filing Date:
October 17, 1973
Export Citation:
International Classes:
B29C37/00; B29C45/00; B29C45/76; B29C45/77