Resin switching assist method and apparatus for molding machine

A resin switching assist method for a molding machine, the method assisting an operator in performing a resin switching process of discharging a former resin from a heating cylinder and then supplying a succeeding resin to the heating cylinder, the method comprising:

• in advance of the resin switching process, for each of different resins, estimating a zero shear viscosity of each resin by using a conversion function expression whose parameters are a melt flow rate and a set temperature of the heating cylinder, registering the estimated zero shear viscosity in a first database in a molding machine controller, and registering a purge resin required amount in a second database in the molding machine controller, the purge resin required amount corresponding to a viscosity difference between the zero shear viscosity of the former resin and the zero shear viscosity of the succeeding resin;
• and
• in the resin switching process, obtaining the zero shear viscosity of the former resin and the zero shear viscosity of the succeeding resin from the first database by inputting a melt flow rate of the former resin and a melt flow rate of the succeeding resin to the molding machine controller, obtaining a viscosity difference between the zero shear viscosity of the former resin and the zero shear viscosity of the succeeding resin, obtaining an amount of a purge resin required for resin switching, as a purge resin required amount, from the second database, and displaying at least the obtained purge resin required amount.