External sensor kit for injection molding apparatus and methods of use

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 nozzle arranged to inject the shot of molten thermoplastic material into the mold cavities;
• a strain gauge sensor on a coupon secured against the mold cavity;
• a hammer configured to impart a force to the coupon when the mold cavity is closed;
• a controller communicatively connected to the ram and nozzle and the strain gauge sensor;
• a virtual cavity sensor, implemented as a set of instructions that are stored on a non-transitory machine-readable medium, to determine at least one of an approximate pressure or melt flow front location using an output of the strain gauge sensor, wherein the injection molding apparatus adjusts an operation of the ram in view of the determined approximate pressure or melt flow front location.

A method of retrofitting an injection molding apparatus with an external sensor kit comprising:

• drilling at least one hole in a first mold side;
• securing a bracket to the first mold side;
• securing a coupon between the bracket and the first mold side;
• drilling at least one hole in a second mold side;
• securing a hammer to the second mold side.

A method of injection molding, comprising:

• amplifying a change in strain in a coupon secured to a mold side of a mold cavity;
• measuring, using a strain gauge sensor, the change in strain in the coupon;
• approximating at least one of a pressure or a melt flow front location within the mold cavity based on the change in strain;
• comparing the approximated pressure or melt flow front location to a trigger point;
• and,
• if the approximated pressure or melt flow front location equals or exceeds the trigger point, activating a virtual cavity sensor, wherein upon activation, the virtual cavity sensor causes a controller to perform an action.