A mold assembly (1) for injection molding of a plastic pipe fitting (2, 3). The pipe fitting comprises an elbow-shaped or a tee-shaped internal flow channel (4). At least one of the first core member (14) and the second core member (15) of the core package (12, 13) comprises a built-in cooling arrangement (20) for cooling of the core package (12, 13), the cooling arrangement (20) extending longitudinally inside said core member over a substantial length of said core member. The pipe fitting (2, 3) comprises an elbow-shaped or tee-shaped internal flow channel (4) comprising at least two channel parts (5, 6, 7) arranged at a first angle (α) in relation to each other, the channel parts (5, 6, 7) each having a circular cross-section and a smoothly radiused inner corner face (8) between each two channel parts being at said first angle in relation to each other, the at least one of the channel parts having an inner diameter D, a length L from central corner point to the end of the channel part, the inner corner face having a rounding radius R. The ratio (D/R) of the inner diameter D and the rounding radius R is in the range 2 to 5, and the ratio (L/D) of the length L and inner diameter D is in the range 8 to 3.

A mold assembly (1) for injection molding of a plastic pipe fitting (2, 3). The pipe fitting comprises an elbow-shaped or a tee-shaped internal flow channel (4). At least one of the first core member (14) and the second core member (15) of the core package (12, 13) comprises a built-in cooling arrangement (20) for cooling of the core package (12, 13), the cooling arrangement (20) extending longitudinally inside said core member over a substantial length of said core member. The pipe fitting (2, 3) comprises an elbow-shaped or tee-shaped internal flow channel (4) comprising at least two channel parts (5, 6, 7) arranged at a first angle (α) in relation to each other, the channel parts (5, 6, 7) each having a circular cross-section and a smoothly radiused inner corner face (8) between each two channel parts being at said first angle in relation to each other, the at least one of the channel parts having an inner diameter D, a length L from central corner point to the end of the channel part, the inner corner face having a rounding radius R. The ratio (D/R) of the inner diameter D and the rounding radius R is in the range 2 to 5, and the ratio (L/D) of the length L and inner diameter D is in the range 8 to 3.

A mould tool comprising: a first tool part defining a first mould cavity portion; a second tool part defining a second mould cavity portion; and, a cavity alignment system comprising: a temperature control system configured to control the temperature of a first zone of the first tool part to thereby effect thermal expansion and/or contraction in the first zone of the first tool part; a sensor configured to measure movement of a part of the first tool part in response to the said thermal expansion and/or contraction; and, a controller configured to control the temperature control system in response to feedback from the sensor to thereby control the position of the first mould cavity portion relative to the second mould cavity portion.

A mould tool comprising: a first tool part defining a first mould cavity portion; a second tool part defining a second mould cavity portion; and, a cavity alignment system comprising: a temperature control system configured to control the temperature of a first zone of the first tool part to thereby effect thermal expansion and/or contraction in the first zone of the first tool part; a sensor configured to measure movement of a part of the first tool part in response to the said thermal expansion and/or contraction; and, a controller configured to control the temperature control system in response to feedback from the sensor to thereby control the position of the first mould cavity portion relative to the second mould cavity portion.

Heating device for locally heating of an injection mold cavity wall, comprising: a base plate, an actuator located on the base plate, to perform a linear movement; a heated stamp connected to the actuator and driven by the actuator, to perform a linear movement in direction to and from the injection mold cavity wall; wherein the heated stamp is located below the base plate and the actuator is located on top of the base plate, and wherein the base plate comprises an opening through which a pin extends for transferring the linear movement from the actuator to the heated stamp.

Heating device for locally heating of an injection mold cavity wall, comprising: a base plate, an actuator located on the base plate, to perform a linear movement; a heated stamp connected to the actuator and driven by the actuator, to perform a linear movement in direction to and from the injection mold cavity wall; wherein the heated stamp is located below the base plate and the actuator is located on top of the base plate, and wherein the base plate comprises an opening through which a pin extends for transferring the linear movement from the actuator to the heated stamp.

An optical element is configured to transmit a light flux emitted from a light source having a single light source wavelength, and is formed from a material in which resin and glass fillers are mixed. A difference between respective refractive index change rates (dn/dT) of the resin and the glass fillers relative to a temperature change at least in a vicinity of the light source wavelength becomes 10.5×10.sup.5 or less.

An optical element is configured to transmit a light flux emitted from a light source having a single light source wavelength, and is formed from a material in which resin and glass fillers are mixed. A difference between respective refractive index change rates (dn/dT) of the resin and the glass fillers relative to a temperature change at least in a vicinity of the light source wavelength becomes 10.5×10.sup.5 or less.

Injection molding utilizing targeted heating of mold cavities when in a non-molding position, thereby facilitating enhancement of the appearance and strength of injection molding parts in a manner that does not significantly increase cycle times or energy consumption.

Injection molding utilizing targeted heating of mold cavities when in a non-molding position, thereby facilitating enhancement of the appearance and strength of injection molding parts in a manner that does not significantly increase cycle times or energy consumption.