Injection molding machine, additive manufacturing apparatus, and pressure control method

An injection molding machine comprising:

• a cylinder that accommodates a molten resin;
• a discharging nozzle that is communicated with the cylinder;
• a piston configured to discharge the molten resin from the discharging nozzle by sliding in the cylinder and pressurizing the molten resin in the cylinder;
• and
• one or more processors configured to
• calculate a target pressure that is a target value used for pressurizing the molten resin in the cylinder and at which a flow rate of the molten resin discharged from the discharging nozzle becomes an indicated flow rate;
• acquire a temperature of the molten resin in the cylinder;
• acquire a pseudo-plastic viscosity corresponding to the temperature of the molten resin;
• control a pressure of the molten resin in the cylinder such that the pressure becomes the target pressure, the target pressure is calculated based on the indicated flow rate, the temperature of the molten resin, the pseudo-plastic viscosity, and a size of the discharging nozzle, the pressure of the molten resin is controlled by controlling a movement speed of the piston, and the controlling the movement speed of the piston is based on a bulk modulus of the molten resin;
• and
• modify the bulk modulus only when a difference between a pressure change amount and the target pressure is equal to or higher than a predetermined value, the pressure change amount calculated from an actually measured pressure and a substantially pressurized volume,
• wherein the substantially pressurized volume is calculated by subtracting an outflow rate multiplied by a predetermined interval of time from a volume that shrinks as the piston moves during the predetermined interval of time.