Malfunction-detecting method in injection molding machines

A malfunction-detecting method in electric injection molding machines, in which a molded product is removed from a mold by using an ejector pin in an ejecting step, said method comprising the steps of:

• storing in advance a relationship between the position of ejector pin or the rotational angle of an ejector pin driving motor and torque of the ejector pin driving motor as a reference pattern, said relationship having been obtained from good results in the removal of the molded product;
• presetting a tolerance limit of the torque with respect to said reference pattern;
• and
• monitoring a pattern of said torque, relative to said position or said rotational angle during the ejecting step, and generating an alarm at the time when the value of said torque falls outside said tolerance limit.

A malfunction-detecting method in hydraulic injection molding machines, in which a molded product is removed from a mold by using of an ejector pin in an ejecting step, said method comprising the steps of:

• storing in advance a relationship between the position of ejector pin and hydraulic pressure of an ejector pin-driving hydraulic pump as a reference pattern, said relationship having been obtained from good results in the removal of the molded product;
• presetting a tolerance limit of the hydraulic pressure with respect to said reference pattern;
• and
• monitoring a pattern of said hydraulic pressure, relative to said position, during the ejecting step, and generating an alarm at the time when the value of said hydraulic pressure falls outside said tolerance limit.