| 摘要 |
PURPOSE:To improve dimensional and weight precision of a molded article as well as molding yield by so controlling the pressure holding time for each shot that the time integral of cavity pressure may be constant. CONSTITUTION:Cavity pressure is detected by a pressure sensor 9 fitted in a cavity 7, and the detection signal is fed to a microcomputer 11 through an analog-to-digital converter 10. A cavity pressure profile ABCD (A: start of resin injection; B: completion of injection; C to D: a step where a holding pressure is loaded for preventing a molded article from shrinking; D: gate seal point) is so controlled that the time integral Q(t) of cavity pressure may be constant irrespective of changes in resin temperature, mold temperature, resin lot number, and the like. That is, the integral Q(t) is compared with a setpoint in a pressure integrated-value setter 12, and a holding pressure cut-off device 15 releases the holding pressure in an injector to control the pressure holding time when the two compared values are equal. |
