How Sensors Monitor Tool Respiration In Die Casting Machines

Video: How Sensors Monitor Tool Respiration In Die Casting Machines

Aluminum die-cast parts combine strength with low weight. They are also extremely conductive and highly corrosion-resistant. Precision is required when processing the material, especially when it comes to monitoring tool respiration in die-cast aluminum. This is a quality-determining factor that also affects the durability of the tool.

If aluminum die-cast parts are manufactured, a high pressure of approximately 600 bar to 1000 bar is necessary in order to press the liquid material, which is around 700 ° to 900 ° hot, into a preheated steel mold. The shot time is only about 50 ms to 100 ms. The shape in which the aluminum is pressed consists of two mold halves that are held together with enormous force of over 1000 tons of pressure. When injecting, the high pressure creates a small gap between the mold halves. This process is called tool breathing. If this gap becomes too large, this has a negative impact on the manufacturing process, because fraying of the component occurs, which are referred to as tinsel.

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Loss of time due to incorrect tool breathing

The manufacturers place high quality requirements on the production process, which is why tinsel has to be reworked and inevitably leads to loss of time and high follow-up costs. Another negative aspect is aluminum residues that remain on the tool. They lead to increased wear and thus reduce the service life of the tool.

Simple, quick and reliable monitoring of mold respiration is achieved by inductive sensors based on eddy current from Micro-Epsilon. The sensors of the Eddy NCDT 3005 series are ideally suited for such applications because of their robust construction, the good price-performance ratio and their compactness. Thanks to their advanced sensor technology, they ensure continuous and high-precision gap monitoring and thus a more efficient manufacturing process.

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Precise measurement of tool breathing

As a rule, three to four eddy current systems are attached to the monitoring of the tool respiration, which determine the expansion or the gap opening of the tool with micrometer accuracy. A measuring system consists of a compact and robust controller that forms a fixed unit together with the cable and the sensor. This integrated system structure increases robustness and resistance to external factors. The system is thus protected against the harsh industrial environment with high temperatures of up to 100 ° at the sensor, dust, dirt, vibrations and pressure and delivers precise measurement results regardless of the environment. The compact design of the systems enables simple integration even in existing systems.

Sensors matched to the manufacturing process

Eddy current-based sensors from Micro-Epsilon are matched to the high requirements in the manufacturing process of die-cast aluminum parts due to their design and technology. In contrast to conventional inductive sensors, they are characterized by their high accuracy, cut-off frequency and temperature stability. Depending on the model, the systems can withstand temperatures of up to 200 ° C. Thanks to the active temperature compensation, they deliver highly accurate results even when the temperature fluctuates.

In addition, movements are recorded very quickly with a measuring frequency of up to 5 kHz. Another positive aspect is the user-friendliness and the good price-performance ratio, which predestines the sensors for OEM and series applications. With higher quantities, adjustments to customer requirements are also possible.

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Eddy current based measurement method

The eddy current measuring principle occupies a special position among the inductive measuring methods. The effect for measurement via eddy current is based on the withdrawal of energy from an oscillating circuit. This energy is required to induce eddy currents in electrically conductive materials. Here, a coil is fed with alternating current, whereupon a magnetic field is formed around the coil. If there is an electrically conductive object in this magnetic field, eddy currents, which form a field, arise in it, according to Faraday's law of induction. This field counteracts the field of the coil, which results in a change in the coil impedance. This impedance can be tapped as a measurable variable on the controller as a change in the amplitude and phase of the sensor coil.