Patent ID: 9073255
Filing Date: 2015-07-07
Classification: B29C

Abstract:
1. A method for controlling a plasticizing capability in an electric-motor driven injection molding machine having a plasticizing mechanism which consists of a screw revolution drive system where rotation of a servomotor for plasticization is transferred to rotation of a screw through a reduction gear and resin pellets fed through a hopper are melted by the rotation of said screw and a given amount of melted polymer is stored at the end of a barrel and a screw injection drive system where rotation of a servomotor for injection is transferred to rotation of a ball screw through a reduction gear and rotation of said ball screw is converted to a linear motion of a nut of said ball screw and said screw is moved back and forth through a moving part drived by a movement of said nut and pressure application to the melted polymer stored at the end of said barrel is realized by the movement of said screw and the pressure applied to the melted polymer is referred to as a screw back pressure, comprising: deriving an estimate of screw back pressure {circumflex over (x)} where x where k: Discrete variable representing a discrete-time t where {circumflex over (x)} providing a high-precision detection means for said estimate of screw back pressure which makes the effects of the errors of said mathematical model of said plasticizing mechanism on the estimation error small enough and enables said estimation of screw back pressure to be high-precision wherein the equation (122) is used to show that the estimation error {tilde over (η)} caused by the model errors δ where {tilde over (η)} providing a detection means having very small time-lag for said estimate of screw back pressure which makes the estimation error tend to zero rapidly and enables said estimate of screw back pressure to be detected with very small time-lag wherein the equation (126) given as the time responses of the equation (125) is used to show that the estimation errors {tilde over (η)} where t: Time variable, C deriving a difference signal between a screw back pressure command signal from a screw back pressure setting device and said estimate of screw back pressure from said high-gain observer by using a subtracter; and deriving a motor current demand signal applied to said servomotor for injection by using a pressure controller to which said difference signal is fed from said subtracter so that said estimate of screw back pressure follows said screw back pressure command signal by generating a motor torque of said servomotor for injection corresponding to said motor current demand signal and by realizing a given screw back pressure.