Dimension-control and clamp reduction during injection molding of laminated products

A method of reducing the clamping force required to produce a plastic product having laminated walls injection molded within a cavity of a mold having a first mold section and a second mold section defining the cooling cavity therebetween, comprising providing in advance an early layer of the laminated plastic product encased in the mold cavity and further comprising the steps of:

• (a) injecting a first plastic material into the mold cavity which encases the early layer so that only a region of the early layer is coated by the injected first plastic material;
• (b) cooling the injected first plastic material in the mold cavity to solidify a portion of the first plastic material in a section of the mold cavity extending between the first mold section and the second mold section;
• (c) injecting a second plastic material under pressure into the mold cavity subsequent to solidifying said portion of the first plastic material, so that the cooled injected first plastic material in combination with the early layer of said region impedes transmission of injection pressure caused by injecting the second plastic material to thereby reduce during injection of the second plastic material the clamping force required to overcome forces that tend to separate the first and second mold sections as a result of injection pressure, whereby the injected second plastic material further fills the mold cavity, thereby further coating the early layer;
• and
• (d) cooling the injected plastic material in the mold cavity to thereby solidify the product;
• wherein step (a) comprises the step of:
• (e) continuing the injection of the first plastic material by the second plastic material without intermission.

A method of controlling the dimensions of a hollow plastic product having laminated walls injection molded in a cavity of a mold having a core section and a cavity section defining the mold cavity therebetween, comprising stabilizing the core section in relation to the cavity section and comprising the steps of:

• (a) injecting a first plastic material into the mold cavity;
• (b) cooling the injected first plastic material in the mold cavity;
• (c) injecting subsequent to injecting the first plastic material, a second plastic material into the mold cavity so that the cooled injected first plastic material extending between the core section and the cavity section is sufficiently solidified to stabilize the core section in relation to the cavity section by impeding movement of the core section in relation to the cavity section caused by injecting the second plastic material, whereby the injected second plastic material further fills the mold cavity;
• (d) cooling the injected plastic material in the mold cavity to thereby provide an early layer of the laminated plastic product;
• and
• (e) encasing the early layer in a second mold cavity and injecting additional plastic material into the second mold cavity thereby coating the early layer with the additional plastic material to mold the laminated plastic product;
• wherein step (a) comprises the step of:
• (f) continuing the injection of the first plastic material by the second plastic material without intermission.

A method of reducing the clamping force required to produce a plastic product having laminated walls injection molded in a cavity of a mold having a first mold section and a second mold section defining the cooling cavity therebetween, comprising

• (a) injecting a first plastic material into the mold cavity;
• (b) cooling the injected first plastic material in the mold cavity to solidify a portion of the first plastic material in a section of the mold cavity extending between the first mold section and the second mold section;
• (c) injecting a second plastic under pressure into the mold cavity subsequent to solidifying said portion of the first plastic material, so that the cooled injected first plastic material impedes transmission of injection pressure caused by injecting the second plastic material, to thereby reduce during injection of the second plastic material the clamping force required to overcome forces that tend to separate the first and second mold sections as a result of injection pressure, whereby the injected second plastic material further fills the mold cavity;
• (d) cooling the injected plastic material in the mold cavity to thereby provide an early layer of the laminated product;
• and
• (e) encasing the early layer in a second mold cavity and injecting additional plastic material into the second mold cavity thereby coating the early layer with the additional plastic material to mold the laminated plastic product;
• wherein step (a) comprises the step of:
• (f) continuing the injection of the first plastic material by the second plastic material without intermission.

A method of controlling the dimensions of a hollow plastic product injection molded within a cavity of a mold having a core section and a cavity section defining the mold cavity therebetween, comprising the steps of:

• (a) injecting a first plastic material into the mold cavity;
• (b) cooling the injected first plastic material in the mold cavity;
• (c) injecting subsequent to injecting the first plastic material, a second plastic material into the mold cavity so that the cooled injected first plastic material is sufficiently solidified to stabilize the core section in relation to the cavity section by impeding movement of the core section in relation to the cavity section caused by injecting the second plastic material, whereby the injected second plastic material further fills the mold cavity;
• and
• (d) cooling the injected plastic material in the mold cavity to thereby solidify the molded product;
• wherein step (a) comprises the step of:
• (e) continuing the injection of the first plastic material by the second plastic material without intermission.

A method of reducing the clamping force required to produce a plastic product injection molded within a cavity of a mold having a first mold section and a second mold section defining the cooling cavity therebetween, comprising the steps of:

• (a) injecting a first plastic material into the mold cavity;
• (b) cooling the injected first plastic material in the mold cavity to solidify a portion of the first plastic material in a section of the mold cavity extending between the first mold section and the second mold section;
• (c) injecting a second plastic material under pressure into the mold cavity subsequent to solidifying said portion of the first plastic material, so that the cooled injected first plastic material impedes transmission of injection pressure caused by injecting the second plastic material to thereby reduce during injection of the second plastic material the clamping force required to overcome forces that tend to separate the first and second mold sections as a result of injection pressure, whereby the injected second plastic material further fills the mold cavity;
• and
• (d) cooling the injected plastic material in the mold cavity to thereby solidify the product;
• wherein step (a) comprises the step of:
• (e) continuing the injection of the first plastic material by the second plastic material without intermission.