Injection molding control

Claim 1

An automatic control system for injection molding machines having a reciprocable ram for injecting plasticized materials from an extrusion barrel into a mold cavity, said system comprising a position transducer producing a position signal varying with the position of the ram, a position setpoint means establishing a position setpoint signal, a position sample timer producing a position sample signal at a predetermined time after initiation of an injection cycle, a position comparator supplying a position deviation signal in response to deviation of said position signal from the position setpont signal upon occurrence of said position sample signal, means for adjusting a fill pressure in compliance with the position deviation signal to compensate for said position deviation, a pressure transducer producing a pressure signal varying with the pressure in said mold cavity, a pressure setpoint means establishing a pressure setpoint signal, a pressure sample timer producing a pressure sample signal at a predetermined second time after initiation of the injection cycle, a pressure comparator supplying a pressure deviation signal in response to deviation of said pressure signal from the pressure setpoint signal upon occurrence of said pressure sample signal, and means for adjusting a compaction pressure in compliance with the pressure deviation signal to compensate for said pressure deviation, said position sample signal being produced prior to completion of filling of the mold cavity, and said pressure sample signal being produced after completion of filling of the mold cavity.