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Advanced Engineering 2021

NEC Birmingham(B40 1NT)

03/11/2021 - 04/11/2021

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Inductive proximity sensors designed to go the distance

Inductive proximity sensors designed to go the distance

When Turck presented the first Uprox Factor 1 sensor back in 1994, conventional inductive proximity switches had already been in use for around 40 years. Customers quickly realised the many advantages of the first Uprox devices, as they considerably reduced the inventory of different sensor types required to reliably sense ferrous and non-ferrous metals. With Uprox, one proximity switch offered the same switching distance for all metals.

At that time, the new air coil system, used in Uprox, was superior to the conventional ferrite core in virtually every situation. Besides the Factor 1 features, it also provided extremely high magnetic field immunity that allowed the sensors to be operated, without the problems of false switching, in the proximity of electric welding plants, induction ovens or linear drives. The classical Uprox principle consists of a transmitter coil and two receiver coils, and is considered as the forefather of all differential transformer sensor systems.

The developers of the Uprox+, which Turck presented in 2004, furthered this idea and used two pairs of transmitter and receiver coils directly on the chip in order to increase the effective signal. This second generation offered the benefits of larger switching distances together with designs and mounting options that were previously unheard of. 

Uprox3 sensors are the third generation of Turck’s Uprox Factor 1 sensors. Although the existing Uprox sensors offered large switching distances for all metals, these distances are now increased by as much as 50% in the new sensors. It was previously unattainable to sense 3mm in the M8 design, 6mm in M12, and 10mm in M18. However, thanks to the continuous development of its Uprox technology, Turck has been able to achieve these larger switching distances without any compromises in performance. Because of their inherent immunity 

to magnetic fields, Uprox3 series sensors are suitable for use in many demanding industrial sectors, such as welding for the automotive and metal forming markets as well as the rail industry. The new Uprox3 series is available with robust PTFE coated sensors in M8, M12 and M18 designs (Weldguard coated versions are also be available). Like their predecessors, all Uprox3 sensors offer high EMC stability and flexible mounting, including full flush mounting, as well as precise switching points. 

A further enhancement of the Uprox3 series is the inclusion of IO-Link enabled sensors in M12 and M18 barrel sizes, giving variable switching options, temperature monitoring and identification capabilities.

In field tests at various car manufacturing plants, where the previous 8mm switching distance of the M18 Uprox+ was reaching its limits, the new Factor 1 sensor proved to be a perfect enhancement.

In the automotive industry vacuum grippers are frequently used for picking up and moving sheet metal. Suction cups are applied to the sheets and a negative pressure is generated. An inductive sensor close to one of the suction cups detects whether the gripper was able to grip the metal or not. 

However, the sensor cannot be mounted too close to the target otherwise it may be damaged when a sheet is picked up. 

A safety distance of 1 to 2mm must be ensured. When the gripper then moves with the held sheet, the rubber suction cups are expanded by the weight and the inertia of the sheet. Depending on the acceleration and weight of the sheet, the suction cups may be extended so much that the proximity switches, previously used, could no longer detect the target, resulting in a switching error.

To reduce the speed of the process is not an option, and so the larger switching distance of the Uprox3 solves a critical problem here. The larger switching distance of the Uprox3 makes a significant contribution to more reliable and efficient production processes.

The welding spark resistant M8, M12 and M18 variants with PTFE-coated housings are ideal for welding applications, particularly in the automotive sector. As with previous generations, the design of all Uprox3 sensors provides them with an extremely good EMC performance and immunity to magnetic fields. The coating reliably prevents welding spatter from sticking and building up on the sensor face.

It was the Greek philosopher, Heraclitus, who proclaimed: “The only constant is change.” This certainly applies to Turck with the company’s dedication to continually build on its success across all of its product ranges. The opinion, expressed by some, that inductive proximity sensors are now ‘mature technology’ has been proved wrong by Turck as it constantly strives to develop innovative products. 

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