Anomaly monitoring method of an injection molding machine

An anomaly monitoring method of an injection molding machine which monitors anomaly in a measurement process, comprising:

• executing a main measurement process which performs a measurement by forward rotating a screw having a back-flow prevention valve installed on a tip of the screw;
• executing a post-measurement process which performs a post-measurement processing for closing said back-flow prevention valve after the main measurement process ends,
• executing an injection process wherein said screw is put in a freely-rotatable state and is moved forward after said post-measurement processing ends,
• detecting an amount of rotation of said screw since a start of the injection process, and
• if the detected amount of rotation exceeds at least a preset amount, executing an anomaly processing,
• wherein the back-flow prevention valve is mounted in a freely displaceable manner on a valve mounting axis unit which is located between a screw head and a flight side of the screw, an inner diameter of the back-flow prevention valve being larger than an outer diameter of the valve mounting axis unit,
• wherein during the injection process, the back-flow prevention valve is pressed against a flat, ring-shaped rear face of the screw head and
• wherein in said post-measurement process after said main measurement process ends, said screw is put in a freely-rotatable state and moved forward, a rotation state of said screw during the forward movement is monitored, and when the rotation of said screw stops, said screw is rotated in reverse by a specified amount of reverse rotation.