Abstract: A process for controlling part density in molding machines in which a charge of material is injected by a ram into the mold cavity in approximatey 1.5 seconds or less as the ram moves between a variable retraction point and a fixed forward point whereat the ram bottoms, i.e., reaches its forwardmost point of travel beyond which further forward motion is precluded by mechanical limits or stops. Means are included to determine the pressure of the material injected into the mold cavity, using a pressure transducer communicating with the cavity, runner or barrel, at the point in time when the ram bottoms. The measured pressure is then compared against a predetermined pressure correlated to a desired part density, and in response thereto an error signal generated.

Abstract: Two embodiments of closed loop electro-fluidic controlled systems are disclosed for controlling the velocity, acceleration, torque, force of pressure applied to a member. The system includes a source of electrical command signals correlated to the desired magnitude of the parameter being controlled, a transducer responsive to the controlled member for providing an electrical feedback signal correlated to the actual value of the parameter, and a circuit for providing an error signal correlated in magnitude and polarity to the magnitude and sense of the difference between the actual and desired values of the controlled parameter. Also included is a transducer responsive to the error signal for applying a positioning force to a movable valve closure element, which is subjected to no other forces, to regulate the application of pressurized fluid through the valve to the controlled member in dependence upon the error signal.

Abstract: Two embodiments of closed loop electro-fluidic controlled systems are disclosed for controlling the velocity, acceleration, torque, force or pressure applied to the member. The system includes a source of electrical command signals correlated to the desired magnitude of the parameter being controlled, a transducer responsive to the controlled member for providing an electrical feedback signal correlated to the actual value of the parameter, and a circuit for providing an error signal correlated in magnitude and polarity to the magnitude and sense of the difference between the actual and desired values of the controlled parameter. Also included is a transducer responsive to the error signal for applying a positioning force to a movable valve closure element, which is subjected to no other forces, to regulate the application of pressurized fluid through the valve to the controlled member in dependence upon the error signal.

Abstract: An injection molding control provides for the programmable control of ram velocity as a function of the position of the ram through closed-loop feed-back of the measured actual velocity. Closed-loop feed-back of the actual mold cavity pressure overrides the velocity program in an analog fashion to stop the ram when a preset cavity pressure has been attained associated with a desired charge size. Programmable control of the ram screw speed and/or back pressure during injection as a function of ram position or time is used to impart a predetermined temperature profile to the charge along the length thereof while it is in the barrel prior to injection. This enables controlled variation in density of the molded article throughout its volume to achieve desired levels in preselected characteristics such as surface wear, gloss, resolution and the like.

Abstract: A circuit for analog adjustment of a machine including a programming means to generate a fixed number of discrete control voltages. Each programmed control voltage corresponds to the desired machine control voltage at a particular moment of time in the cycle of the controlled machine. A staircase voltage is generated during the time period between two successive moments in the machine cycle, i.e., a machine cycle interval at which the control voltage is defined. The staircase voltage starts during each machine interval at the programmed control voltage corresponding to one moment of time in the machine cycle at the beginning of a particular machine cycle interval and ending, at the beginning of the next machine cycle interval, at the programmed control voltage for the moment of time corresponding to the beginning of the next machine cycle interval.