Patent ID: 7144531

Claim:
A resin evaluation method using an injection molding machine comprising: performing a first predetermined number of air shot injections of molten resin with constant injection velocity and different values of resin temperature automatically altered successively for the respective air shot injections, and with resin pressure and injection screw position, or resin pressure and injection time elapsed from start of the injection as the injection screw is advanced, being measured for the respective air shot injections; performing a second predetermined number of air shot injections of molten resin with constant resin temperature and different values of injection velocity automatically altered successively for the respective air shot injections, and with resin pressure and injection screw position, or resin pressure and injection time elapsed from start of the injection as the injection screw is advanced, being measured for the respective air shot injections; and evaluating characteristics of the molten resin by automatically obtaining at least one of a degree of resin-temperature dependency of variation of the resin pressure in the air shot injections, and a degree of velocity or flow-rate dependency of variation of the resin pressure in the air shot injections, based on either a relationship between the resin pressure and the screw position or a relationship between the resin pressure and the injection time, measured in the air shot injections.