Injection molding machine using servo motor and having mold protecting function

Claim 1

A mold injecting machine using a servo motor and having a mold protecting function, comprising: a clamp mechanism for operating a mold to perform mold clamping; a servo motor, coupled to said clamp mechanism, for driving said clamp mechanism; a position detector, coupled to said servo motor, for detecting a positon of the mold and producing a detection output; and an NC control unit, coupled to said servo motor and said position detector, for controlling said servo motor, said NC control unit having a torque limit function for suppressing a torque output from said servo motor below a predetermined value, said NC control unit including: means for inputting a preset mold protection start position, a preset mold contact position and a preset predetermined time period, the preset predetermined time period being set to a value sufficient for allowing the mold to move from the preset mold protection start position to the preset mold contact position when no foreign matter exists in the mold; mold position discriminating means for discriminating whether the preset mold protection start position and the preset mold contact position have been reached based on the detection output from said position detector; elapsed time discrminating means for discriminating whether the preset predetermined time period has elapsed after a point in time at which the mold reaches the preset mold protection start position; and alarm means for generating an alarm when the predetermined period of time has elapsed before the mold reaches the preset mold contact position.