Method and apparatus for injection molding

A method for injection molding articles comprising the sequential steps of:

• a) providing an injection molding machine with a plurality of mold cavities;
• b) injecting a molten material into a first mold cavity at a first fill rate until the first mold cavity is substantially filled with molten material or until the molten material inside said first mold cavity reaches a set-point holding pressure;
• c) reducing or eliminating an injection pressure applied to said molten material;
• d) injecting said molten material into a second mold cavity at a second fill rate until the second mold cavity is substantially filled with molten material or until the molten material inside said second mold cavity reaches a set-point holding pressure;
• e) holding said molten material at said set-point pressure inside said plurality of mold cavities until said molten material cools and solidifies into molded articles;
• and
• f) ejecting said molded articles from said injection molding machine.

A method for injection molding articles comprising:

• a) providing an injection molding machine with a plurality of mold cavities and a resin feeding screw;
• b) injecting a molten material into a first mold cavity at a first fill rate until said first mold cavity approaches a velocity to pressure switchover point, said molten material being injected by a first injection pressure that is applied to the molten material by the resin feeding screw;
• c) reducing the first injection pressure that is applied to the molten material by the resin feeding screw;
• d) injecting said molten material into a second mold cavity at a fill rate until the second mold cavity approaches a velocity to pressure switchover point, said molten material being injected by a second injection pressure that is applied to the molten material by the resin feeding screw;
• e) holding said molten material inside said plurality of mold cavities until said molten material cools and solidifies into molded articles;
• and
• f) ejecting said molded articles from said injection molding machine.

A method for injection molding articles comprising:

• a) providing an injection molding machine with a plurality of mold cavities and a resin feeding screw;
• b) injecting a molten material into a first mold cavity at a first fill rate until said first mold cavity is substantially filled and said molten material is held at a holding pressure for a period of time, said molten material being injected by a first injection pressure that is applied to the molten material by the resin feeding screw;
• c) closing said first mold cavity;
• d) reducing the first injection pressure that is applied to the molten material by the resin feeding screw;
• e) opening a second mold cavity;
• f) injecting said molten material into said second mold cavity at a second fill rate until the second mold cavity is substantially filled and said molten material is held at a holding pressure for a period of time, said molten material being injected by a second injection pressure that is applied to the molten material by the resin feeding screw;
• g) closing said second mold cavity;
• h) holding said molten material inside said plurality of mold cavities until said molten material cools and solidifies into molded articles;
• and
• i) ejecting said molded articles from said injection molding machine.

A method for injection molding articles comprising:

• a) providing an injection molding machine with a plurality of mold cavities, a resin feeding screw, and a stroke sensor for monitoring the position of the resin feeding screw, the stroke sensor transmitting screw position data to a controller, wherein said resin feeding screw is at a screw starting position, further wherein the controller indicates a first cavity starting position;
• b) injecting a molten material into a first mold cavity at a first fill rate until said first mold cavity approaches a first velocity to pressure switchover point, wherein said resin feeding screw is at a first cavity ending position at said switchover point, further wherein said controller indicates a first cavity filled position;
• c) re-setting said controller from the first cavity filled position to a second cavity starting position;
• d) injecting said molten material into a second mold cavity at a second fill rate until the second mold cavity approaches a second velocity to pressure switchover point, wherein said resin feeding screw is at a second cavity ending position at said switchover point, further wherein said controller indicates a second cavity filled position;
• e) moving said resin feeding screw back to said screw starting position;
• f) holding said molten material inside said plurality of mold cavities until said molten material cools and solidifies into molded articles;
• and
• g) ejecting said molded articles from said injection molding machine.

An injection molding apparatus comprising:

• a mold having at least two mold cavities;
• a molten material inlet system in communication with said at least two mold cavities;
• at least two valves in said molten material inlet, wherein each of said at least two valves are associated with one of said mold cavities;
• and
• a controller adapted to sequentially inject molten material into said mold cavities,
• wherein said controller is further adapted to regulate an injection pressure that is applied to the molten material, said injection pressure being substantially eliminated prior to the injection of molten material into each of said mold cavities.

A controller for use with an injection molding device having a mold with at least two cavities, the controller comprising:

• means for initiating a flow of molten material into a first mold cavity;
• means for reducing the flow of molten material into said first cavity when said first mold cavity is substantially filled with molten material;
• means for initiating a flow of molten material into a second mold cavity;
• and
• means for reducing the flow of molten material into said second cavity when said second mold cavity is substantially filled with molten material,
• means for substantially eliminating an injection pressure applied to said molten material when said first mold cavity is substantially filled and prior to initiating the flow of molten material into said second cavity.