METHOD FOR EVENLY DISTRIBUTING PLASTIC MELT IN A HOT RUNNER SYSTEM USING STRAIN GAUGES

• US 20180001531A1
• Filed: 06/07/2017
• Published: 01/04/2018
• Est. Priority Date: 06/30/2016
• Status: Active Grant

• Current Assignee: Imflux Inc. (The Procter & Gamble Company)
• Original Assignee: Imflux Inc. (The Procter & Gamble Company)
• Inventors: Lawless, III, William Francis, Pollard, Rick Alan, Altonen, Gene Michael, Burns, Brian Matthew
• Granted Patent: US 10,538,023 B2
• Time in Patent Office: Days
• CPC Class Codes: B29C 2945/76103 shrinkage, dilation, dimensional change, warpage
• CPC Class Codes: B29C 2945/76274 runners, nozzles
• CPC Class Codes: B29C 2945/76481 Strain gauges
• CPC Class Codes: B29C 2945/76531 Temperature
• CPC Class Codes: B29C 2945/76745 non-cavity forming parts
• CPC Class Codes: B29C 2945/76752 runners, nozzles
• CPC Class Codes: B29C 2945/76759 manifolds
• CPC Class Codes: B29C 45/1782 Mounting or clamping means for heating elements or thermocouples
• CPC Class Codes: B29C 45/2737 Heating or cooling means therefor B29C45/7331 takes precedence
• CPC Class Codes: B29C 45/2738 specially adapted for manifolds
• CPC Class Codes: B29C 45/77 of velocity or pressure of moulding material
• CPC Class Codes: B29C 45/78 of temperature

Abstract

A hot runner injection molding apparatus, and method of use, is disclosed in which strain gauges are provided in the temperature zones of the hot runner injection molding apparatus and a hot runner controller creates a target strain profile, detects deviations from the target strain profile in any temperature zone based on the strain readings provided by the strain gauges in each temperature zone, and instructs correction of deviations from the target strain profile in any deviating temperature zone by adjusting the heat produced by a heater or heaters in the deviating temperature zone. The target strain profile may be based on a median or average of strain readings provided over time by the strain gauges in each temperature zone. A hollow installation tube for placing the strain gauges in the hot runner injection molding apparatus is also disclosed.

Claims

1. An injection molding apparatus, comprising:

a mold comprising one or more mold cavities;

a ram arranged to form a shot of molten thermoplastic material;

a system nozzle arranged to inject a shot of molten thermoplastic material through a hot runner manifold;

a plurality of hot runner nozzles adapted to receive molten thermoplastic material from the hot runner manifold and inject the molten thermoplastic material into a plurality of mold cavities, each mold cavity connected to one hot runner nozzle;

a plurality of temperature zones, each temperature zone associated with one of the plurality of mold cavities and including at least a portion of the hot runner manifold, the associated mold cavity, and the hot runner nozzle connected to the associated mold cavity;

a plurality of heaters, each heater connected to a hot runner controller, each temperature zone including at least one heater;

and a plurality of strain gauges, each strain gauge in communication with the hot runner controller and each temperature zone provided with at least one strain gauge,

wherein the hot runner control comprises a set of a set of instructions that are stored on a non-transitory machine-readable medium to create a target strain profile, to detect deviations from the target strain profile in any temperature zone based on the strain readings provided by the strain gauges in each temperature zone, and to instruct correction of deviations from the target strain profile in the deviating temperature zone by adjusting the heat produced by the at least one heater in the deviating temperature zone.

2. The injection molding apparatus of claim 1, wherein the target strain profile is based on a median or average of strain readings provided over time by the strain gauges in each temperature zone.

3. The injection molding apparatus of claim 1, wherein the target strain profile is predetermined.

4. The injection molding apparatus of claim 1, wherein the at least one strain gauge provided for each temperature zone is located at least one of:

in the portion of the hot runner manifold associated with the temperature zone, on an outer surface of a mold cavity associated with the temperature zone, and in the hot runner nozzle connected to the mold cavity associated with the temperature zone.

5. The injection molding apparatus of claim 1, further comprising a plurality of thermocouples, each heater associated with a thermocouple connected to the hot runner controller.

6. The injection molding apparatus of claim 4, wherein at least one of the at least one strain gauge provided for each temperature zone is located in an aperture provided in the portion of the hot runner manifold associated with the temperature zone or in the hot runner nozzle connected to the mold cavity associated with the temperature zone, and wherein an alternative material insert made from a material that amplifies the strain experienced by the strain gauge surrounds the aperture.

7. The injection molding apparatus of claim 6, wherein the alternative material insert has a lower flex modulus than the surrounding hot runner manifold.

8. The injection molding apparatus of claim 6, wherein the alternative material insert is one of aluminum, brass, titanium, thermoset plastic, composite, and steel with a lower flex modulus than base steel or a combination of two or more of these materials.

9. The injection molding apparatus of claim 6, wherein a minimum distance must be maintained between a bottom or a side of the aperture and an internal melt flow conduit wall to avoid cracking or leaking through the internal melt flow conduit wall.

10. The injection molding apparatus of claim 9, wherein the minimum distance is at least 0.5 mm.

11. The injection molding apparatus of claim 1, further comprising;

a hollow strain gauge installation tube connected to one of the plurality of strain gauges;

a removable insulator fitted around the top of the hollow strain gauge installation tube;

a wire channel connected to a hollow interior of the hollow strain gauge installation tube.

12. The injection molding apparatus of claim 11, wherein the hollow strain gauge installation tube is connected to an extension of one of the plurality of hot runner nozzles.

13. A method of evenly distributing molten thermoplastic material to multiple cavities using a hot runner system in a molding apparatus comprising:

creating, by one or more processors, a target strain profile for a molding process of a molding apparatus;

receiving, by the one or more processors, strain readings reflecting changes in strain during a molding process as an output from at least one strain gauge in each of a plurality of temperature zones of the molding apparatus,

monitoring, by the one or more processors, the strain readings for each temperature zone in order to detect a deviation from the target strain profile by a temperature zone;

if a deviation is detected, determining, by the one or more processors, whether the deviation exceeds a deviation limit;

if the deviation exceeds a deviation limit, adjusting heat produced by one or more heaters in the deviating temperature zone in order to correct the deviation.

14. The method of claim 13, wherein the target strain profile is based on a median or an average of the strain readings provided by the plurality of temperature zones.

15. The method of claim 13, wherein the target strain profile is predetermined.

16. The method of claim 13, wherein at least one of the at least one strain gauge in each of the plurality of temperature zones is located at least one of:

in a portion of a hot runner manifold, on an outer surface of a mold, and in a hot runner nozzle.

17. The method of claim 13, and amplifying the changes in strain sensed by the at least one strain gauge in at least one of the plurality of temperature zones using an alternative material insert.

18. A method of installing a strain gauge in an injection molding system comprising:

connecting a hollow strain gauge installation tube to a strain gauge that has been placed in an aperture;

feeding a wire of the strain gauge through the hollow interior of the hollow strain gauge installation tube and into a wire channel;

turning the hollow strain gauge installation tube until the strain gauge is tightly secured within the aperture;

fitting a removable insulator around the top of the strain gauge installation tube.

19. The method of claim 18, wherein the aperture is located in an extension of a hot runner nozzle.

20. The method of claim 18, and inserting the hollow strain gauge installation tube through a side of a mold.