A partial reflux injection function part 5 is provided according to which resin R at the front side of a screw head portion 4s is injected into the metal mold 2 to fill the metal mold 2 with the resin R in synchronization with the refluxing of a predetermined amount of the reflux resin Rm to be used as a part of the resin R to the screw body part 4m side at the rear side of the screw head portion 4s through the inner side of the screw head portion 4s and/or the outer periphery side of the screw head portion 4s. A control function is provided that sequentially performs a plasticization step Wi1 to rotate the screw 4 in the heating cylinder 3 to thereby subject the resin in the heating cylinder 3 to a plasticization processing; an injection step Wi2 to allow, after the completion of the plasticization step Wi1, the screw 4 to move forward to thereby inject, into the metal mold 2, a part of the plasticized resin R accumulated at the front side of the screw head portion 4s of the screw 4 to fill the metal mold 2 with the resin; and a plasticization promotion step Wi3 to allow, after the completion of the injection step Wi2, a part of the remaining part of the accumulated plasticized resin R to be refluxed as the reflux resin Rm to the rear side of the screw head portion 4s.

A plasticizing device includes a plasticizing cylinder and a plasticizing screw arranged in the plasticizing cylinder. The plasticizing screw is rotatable about, and linearly movable along, a longitudinal axis. The plasticizing screw comprises a functioning section. A sensor is arranged in or on the plasticizing cylinder, and a distance to the surface of the functioning section of the plasticizing screw can be measured by the sensor. A detecting device can detect a type of the functioning section and/or an operating state of the functioning section, can detect a distance signal progression by a movement of the functioning section relative to the sensor, can compare the detected distance signal progression with a stored distance signal progression, and can issue a signal representing the type of functioning section and/or the operating state of the functioning section depending on a matching of the detected distance signal progression with a stored distance signal progression.

A nonreturn valve includes two half-shells, arranged in a portion of the screw with a reduced screw diameter. One or more channels for the melt to flow through from the screw into the space in front of the screw is/are provided in each of the half-shells, the channels lie substantially parallel to the longitudinal axis of the nonreturn valve or of the screw. In each of the channels are a ball and, following the ball in the direction of flow of the melt, a pin arranged substantially transversely to the direction of flow of the melt. In the direction of flow of the melt, the channels have a first channel portion, with a channel diameter less than the diameter of the ball, and a second channel portion, with a channel diameter greater than the diameter of the ball, the ball and the pin are arranged in the second channel portion.

A nonreturn valve includes two half-shells, arranged in a portion of the screw with a reduced screw diameter. One or more channels for the melt to flow through from the screw into the space in front of the screw is/are provided in each of the half-shells, the channels lie substantially parallel to the longitudinal axis of the nonreturn valve or of the screw. In each of the channels are a ball and, following the ball in the direction of flow of the melt, a pin arranged substantially transversely to the direction of flow of the melt. In the direction of flow of the melt, the channels have a first channel portion, with a channel diameter less than the diameter of the ball, and a second channel portion, with a channel diameter greater than the diameter of the ball, the ball and the pin are arranged in the second channel portion.

A method of determining melt flow front travel in a molding apparatus includes setting a sensor threshold, receiving a sensor amount as an output from a sensor monitoring a nozzle of the molding apparatus, and determining that the sensor amount exceeds the sensor threshold. The method further includes receiving a screw location, calculating a travel distance of the screw from the screw location, and calculating melt flow front travel based on the travel distance of the screw. The method further includes receiving, via an interface, an operator generated value for the desired melt flow front travel to be reached, and sending, via an interface, an analog or digital output after the operator generated value has been reached. A method of detecting a leaking condition of a check valve is also included.

A method of determining melt flow front travel in a molding apparatus includes setting a sensor threshold, receiving a sensor amount as an output from a sensor monitoring a nozzle of the molding apparatus, and determining that the sensor amount exceeds the sensor threshold. The method further includes receiving a screw location, calculating a travel distance of the screw from the screw location, and calculating melt flow front travel based on the travel distance of the screw. The method further includes receiving, via an interface, an operator generated value for the desired melt flow front travel to be reached, and sending, via an interface, an analog or digital output after the operator generated value has been reached. A method of detecting a leaking condition of a check valve is also included.

A plasticizing screw for a molding machine, includes a base element which is stretched along a longitudinal axis and a screw tip which is connected to the base element, and the screw tip is located after the base element. A return flow shut-off device includes a first anterior limit stop, a second posterior limit stop, and a shut-off ring movable in a limited manner between the two limit stops along the longitudinal axis. The first, anterior limit stop comprises a first limit stop surface facing towards the base element and the shut-off ring. The shut-off ring comprises a ring-shaped screw tip abutting surface facing towards the first, anterior limit stop. The screw tip abutting surface is formed rotationally symmetric around the longitudinal axis, and the first limit stop surface comprises a convex curvature facing towards the shut-off ring.

An injection moulding machine for producing fibre-reinforced plastic mouldings, having a closing unit and an injection unit, wherein the injection unit has a cylinder and a screw that can be rotated and displaced in the longitudinal direction in the cylinder, the screw having a backflow stop. In the cylinder, filling openings are provided for feeding in a plastic material to be melted and fibre material. To reduce fibre breakage and ensure good mixing, according to the invention a mixing part is provided downstream and/or upstream of the backflow stop, the mixing part being connected to the screw in a rotationally fixed manner for conjoint rotation therewith and having a cylindrical main body with drop-shaped mixing elements arranged thereon.

An injection moulding machine for producing fibre-reinforced plastic mouldings, having a closing unit and an injection unit, wherein the injection unit has a cylinder and a screw that can be rotated and displaced in the longitudinal direction in the cylinder, the screw having a backflow stop. In the cylinder, filling openings are provided for feeding in a plastic material to be melted and fibre material. To reduce fibre breakage and ensure good mixing, according to the invention a mixing part is provided downstream and/or upstream of the backflow stop, the mixing part being connected to the screw in a rotationally fixed manner for conjoint rotation therewith and having a cylindrical main body with drop-shaped mixing elements arranged thereon.

A modular barrel and screw assembly for use in injection molding including a barrel having a barrel body, a separate barrel injection portion and a separate barrel end cap, with the barrel end cap being removably connected to the barrel injection portion and the barrel injection portion being removably connected to the barrel body, and a screw assembly having a screw tip assembly removably connected to a screw portion, wherein an injection chamber having a shot volume is defined by the barrel injection portion, the barrel end cap and the screw tip assembly. The modular barrel and screw assembly enables servicing of the barrel injection portion, barrel end cap and/or screw tip assembly without requiring removal of the barrel body, and enables use of a plurality of alternative corresponding separate barrel injection portions, separate barrel end caps and tip assemblies that provide a plurality of different shot volumes.