Short Shot Detection in an Injection Molding Using Heat Flux Sensors

Principle

A heat flux sensor is highly sensitive and can measure the quantity of heat transfer between the the mould and the injection molding material, without any direct contact. The amount of heat transferred is proportional to the processing parameters and quality of the produced part.

Sensor Location

Heat flux sensors are placed 1 mm beneath the tool cavity, at a 1 mm distance from the material.

The signals transmitted by the sensor are processed in real time by electronic devices which can compare the quantity of heat contributed by every injection. A lower level of heat can be due to absence of material or presence of a colder material caused by problems with mold filling.

Measured Parameter - Local Heat Flux

Local heat flux (W/m²) of injected parts was measured. In the following graph, good parts are indicated by blue crosses. Green vertical lines indicate insufficient heat values.

All parts were checked manually during the tests and bad parts were identified. On the graph, a red line along the picture of defect represents the detection time. Bad parts are detected by the sensor with a green bar before the red ones.

In the manual control, one part may have been missed and is indicated by the red circle at 14:30, and two parts might be considered fragile, the ones at 15:30 and 15:45; but they are not visually detectable.

Heat flux signal during continuous injection cycles. Each peak is associated to the heat transferred during one shot. The red signal corresponds to the output of the electronic device attached to the sensor.

Applications

This system can be applied to large and medium technical parts with high quality expectations and can be easily deployed in production environments for prompt detection. It can find applications in domains such as electro-technical, automotive, packaging, aeronautics, and medical. As the system is highly sensitive to the processing parameters, a default procedure for calibration is available every time the production settings are modified.

About TFX-SA

TFX-SA design and implement in-line material control solutions.

Tfx-Technology® products, also known as Thermoflux are :

• Thermal sensors (Heat Flux sensors or Heat Flow sensors) : there is no mastership over the quality of your products without thermal control. Heat spreads and vehicle information! It is therefore possible to control a product without direct contact.
• Monitoring and control systems
• Industrial acquisition and post processing software
• Traceability of technical operations performed everyday

This information has been sourced, reviewed and adapted from materials provided by TFX-SA.

For more information on this source, please visit TFX-SA.