Method for evenly distributing plastic melt in a hot runner system using strain gauges
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.
1. 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,
and amplifying the changes in strain sensed by at least one of the at least one strain gauge in each of the plurality of temperature zones using an alternative material insert filling an aperture in which the at least one of the at least one strain gauge in each of the plurality of temperature zones is located.
2. The method of claim 1 , wherein the target strain profile is based on a median or an average of the strain readings provided by the plurality of temperature zones.
3. The method of claim 1 , wherein the target strain profile is predetermined.
4. The method of claim 1 , 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.
5. 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; and
filling the aperture with an alternative material insert made from a material that amplifies the strain experienced by the strain gauge.
6. The method of claim 5 , wherein the aperture is located in an extension of a hot runner nozzle.
7. The method of claim 5 , and inserting the hollow strain gauge installation tube through a side of a mold.