For each of different resins R, a zero shear viscosity ?o of each resin R is obtained by using a conversion function expression whose parameters are a melt flow rate (MFR) and a set temperature of a heating cylinder and is registered. Also, a purge resin required amount Wu corresponding to a viscosity difference ?d between the zero shear viscosity ?of of a former resin Rf and the zero shear viscosity ?os of a succeeding resin Rs is registered. When resin switching is performed, the zero shear viscosity ?of of the former resin Rf and the zero shear viscosity ?os of the succeeding resin Rs are obtained by inputting the MFR of the former resin Rf and the MFR of the succeeding resin Rs to a molding machine controller, the viscosity difference ?d between the zero shear viscosity ?of of the former resin Rf and the zero shear viscosity ?os of the succeeding resin Rs is obtained, an amount of a purge resin required for resin switching is obtained as a purge resin required amount Wu, and at least the obtained purge resin required amount Wu is displayed.

A molding cycle stopping method includes: in a case of stopping an operation of a molding cycle in an injection device including a heating cylinder and a screw provided in the heating cylinder, performing a temperature lowering process including lowering a temperature of the heating cylinder from a molding cycle execution temperature to a standby temperature; and performing a continuous purge process including repeatedly purging a resin until a predetermined termination condition is satisfied.

An injection molding machine performs, during a period of a flushing process, a first acquisition process for acquiring a physical quantity for detecting an abnormality of a first drive apparatus.