An injection molding apparatus and method of fabricating a molded part are provided. The apparatus may include a barrel, a nozzle enclosing an end of the barrel and defining an opening in fluid communication with an inside of the barrel, and an extrusion screw positioned at least partially inside the barrel and rotatable relative to the barrel. The extrusion screw may include a screw tip. Relative axial movement between the barrel and the extrusion screw may open or close the opening of the nozzle to permit or prevent, respectively, material flow through the opening of the nozzle. The method may include clamping a mold, opening a nozzle, rotating the extrusion screw to pump a molten material into the mold until the mold is filled, closing the nozzle, and unclamping the mold to release a molded part.

A stepped flight is formed on a screw of an injection molding machine. The stepped flight is a flight in which a step-shaped step portion is formed on a top portion thereof. The top portion of the flight includes a large diameter portion on an upstream side and a land portion on a downstream side. When a gap ratio m of a gap H.sub.1 between the land portion and a bore of the heating cylinder to a gap H.sub.2 between the large diameter portion and the bore is defined as H.sub.1/H.sub.2, the gap ratio m is selected to be 2.3≤m≤6.4.

A stepped flight is formed on a screw of an injection molding machine. The stepped flight is a flight in which a step-shaped step portion is formed on a top portion thereof. The top portion of the flight includes a large diameter portion on an upstream side and a land portion on a downstream side. When a gap ratio m of a gap H.sub.1 between the land portion and a bore of the heating cylinder to a gap H.sub.2 between the large diameter portion and the bore is defined as H.sub.1/H.sub.2, the gap ratio m is selected to be 2.3≤m≤6.4.

A plasticizing device includes a plasticizing section that includes a feeding port for receiving a material and plasticizes the material to generate a melted material, a material feeding section that includes a depositing port communicating with the feeding port and feeds the material from the depositing port to the plasticizing section, and a blowing section that blows gas into a feeding path connecting the depositing port and the feeding port.

A plasticizing device includes a plasticizing section that includes a feeding port for receiving a material and plasticizes the material to generate a melted material, a material feeding section that includes a depositing port communicating with the feeding port and feeds the material from the depositing port to the plasticizing section, and a blowing section that blows gas into a feeding path connecting the depositing port and the feeding port.

A melt dispenser for plastic molding comprises a barrel unit removably mountable to a drive unit. A feed screw is received within a barrel of the barrel unit and is rotated by the drive unit to dispense molten molding material through an outlet of the barrel. A coupling mechanism can be engaged to hold the barrel unit against the drive unit and on to connect the screw to the drive. The coupling mechanism is operable by an actuator.

A melt dispenser for plastic molding comprises a barrel unit removably mountable to a drive unit. A feed screw is received within a barrel of the barrel unit and is rotated by the drive unit to dispense molten molding material through an outlet of the barrel. A coupling mechanism can be engaged to hold the barrel unit against the drive unit and on to connect the screw to the drive. The coupling mechanism is operable by an actuator.

A plasticizing device includes a drive motor, a screw that is rotated by the drive motor and that has a grooved face provided with a groove, a barrel that has an opposed face opposed to the grooved face and that is provided with a communication hole communicating with the groove at the opposed face, a first heating section that heats the material supplied to the groove, a temperature sensor that measures a temperature of the groove, and a control unit that controls the drive motor and the first heating section, wherein the control unit performs a first process for rotating the screw at a first rotation speed by controlling the drive motor, and a second process for rotating the screw at a second rotation speed higher than the first rotation speed by controlling the drive motor, and the control unit controls the first heating section so that a temperature measured by the temperature sensor falls within a predetermined range when performing the first process and the second process.

A plasticizing device includes a drive motor, a screw that is rotated by the drive motor and that has a grooved face provided with a groove, a barrel that has an opposed face opposed to the grooved face and that is provided with a communication hole communicating with the groove at the opposed face, a first heating section that heats the material supplied to the groove, a temperature sensor that measures a temperature of the groove, and a control unit that controls the drive motor and the first heating section, wherein the control unit performs a first process for rotating the screw at a first rotation speed by controlling the drive motor, and a second process for rotating the screw at a second rotation speed higher than the first rotation speed by controlling the drive motor, and the control unit controls the first heating section so that a temperature measured by the temperature sensor falls within a predetermined range when performing the first process and the second process.

A plasticizing device includes a screw that has a grooved face provided with a first groove, a barrel that has an opposed face and a communication hole communicating with the first groove at the opposed face, and a heating section that heats a material supplied to the first groove, wherein the first groove includes a central portion opposed to the communication hole, a material supply portion that is provided at an outer circumference of the grooved face , and a coupling portion that couples the central portion to the material supply portion, a second groove that is coupled to the communication hole is provided and when viewed from the rotational axis direction, an end at the outer circumferential side of the second groove is located inside a track drawn by a boundary line between the material supply portion and the coupling portion when the screw is rotated once.