Method for controlling back pressure in electrically-operated injection apparatus

摘要

A method for controlling back pressure in an electrically-operated injection apparatus wherein rotation and forward movement of an injection plunger within an injection heating tube are carried out by a first electric motor which provides a driving force, wherein backward motion of the injection plunger during the charging of material presses against a screw threaded rotatable part and is thereby converted into rotational motion of the threaded rotatable part, and wherein the rotational motion is controlled to control back pressure of the injection plunger. A second electric motor is used for controlling the back pressure on the injection plunger by controlling rotation of the threaded rotatable part. The backward force exerted on the injection plunger or the direct pressure of the molten material within the injection heating tube are electrically measured. By driving and controlling the second motor through feedback control, the back pressure is made to coincide with a set, preselected back pressure value.