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Advanced Engineering 2021

NEC Birmingham(B40 1NT)

03/11/2021 - 04/11/2021

Join us in our 12th and most important edition to date, as we invite engineers and management from all (more)

Miniature sensors open up a host of new applications

Miniature sensors open up a host of new applications

Miniaturisation makes it possible to accommodate high-performance sensors, including evaluation, inside compact housings with practically the same installation space. This saves installation time and simplifies setup, while IO-Link simplifies parameterisation during operation. As a result, it is often possible to implement new applications.

The devil is in the detail, as the saying goes, and with small sensors it is the detail that make the important difference. Miniature sensors have been on the market for quite some time, the latest designs are opening up many new applications that previously could only be solved using fibre optics or workarounds. Today, these tiny devices only differ from their larger siblings in size and not in performance.

New focusing optics made of PBT/PMMA enable a higher resolution to be achieves, while integrated data evaluation and an IO-Link connection for data transmission and remote configuration make installation, setup and commissioning much easier than before. In addition, with these latest breeds of sensors being mass-produced, they are also an economical alternative to previous fibre optic sensors with their complex technology. The new features open up a whole new range of applications for miniature photoelectric sensors in a wide variety of applications.

Maintaining precise detection even in cramped conditions is a challenge. Small devices such as mini grippers, complex systems or robot arms in particular require extremely tight switching tolerances and offer hardly any space for sensors. Sensors with a diameter of only 4mm can be integrated into even the smallest grippers and fit into narrow gaps. The previous alternative with fibre optic cables is therefore obsolete with a few exceptions. In addition, everything is combined in one compact housing; the time-consuming selection of laser optics, application-specific fibres and matching optics as well as a separate evaluation module is no longer necessary. In contrast to optical fibres, just one extremely flexible electrical cable is installed, which allows even the narrowest bending radii. This increases reliability and saves considerable installation and maintenance costs.

How do miniature sensors prove themselves in practice? A common problem is the optimal positioning of the sensor. A given function must be checked, but the sensor itself must not impair the function. Often, modifications to an existing system are necessary in order to accommodate the sensor. Naturally, the small sensors offer clear advantages here. In one application, for example, standard sensors were being used to detect semi-transparent plastic packaging. Originally, a slot of about 5mm in width had to be widened to about 12mm in places to accommodate the standard sensor, at considerable cost and time. By using a photoelectric miniature sensor with a 4mm diameter, this widening work is no longer necessary, the tiny unit can easily ‘look’ through an existing opening.

The problem cannot always be solved by a simple modification. In many cases, space is simply too limited for conventional sensors. In addition, for example, when using dynamic movements in robot arms or transport systems, there is a requirement for the smallest possible mass combined with flexible connecting cables that permit the tightest bending radii over the long term. The smaller the sensor, the simpler the task of finding an optimum location. In a system for transporting electronic components, for example, these photoelectric miniature sensors have been integrated into each individual gripper element, where they reliably detect the presence and correct position of inserted parts.

Automation saves valuable time and therefore costs in everyday medical practice, especially during standard laboratory operations. However, the devices used are subject to the highest quality requirements, as the health and lives of the patients depend on them. The miniature sensors can also play to their strengths here. In a transport system for clinical laboratory automation, the sensors have to monitor the proper function from below, ie the respective position of carrier platforms, similar to the location display for wagons in the freight station. The small sensor dimensions make it possible to adapt the conveyor path to the function, regardless of the possible installation of the sensor.

In another application example from the assembly industry, small plastic parts must be detected in an automatic transport device. At the end of each cycle, it is necessary to ensure that all pockets of the holder are empty to avoid production issues. The parts, which are only a few millimetres in size, are optically detected and removed if necessary. The challenge here: little space for sensors due to many small holders in a confined space and the simplest possible bundling of the connecting cables on the movable base carrier. Here, the optical mini-sensors offer the advantage of reliably detecting small areas in the smallest of spaces. They are still smaller than the objects to be measured and thus fit into the functional system design without compromise.

The examples shown only give a small insight into the application possibilities of these mini-sensors. They are also in demand in many other areas, solving problem in existing systems due to their performance features. Take, for example, the range of miniature sensors from Contrinex. Despite an external diameter of only 4mm or M5 in threaded versions, the photoelectric sensors offer large, pre-calibrated detection ranges of 12, 24, 60 or 120mm in the diffuse sensing version. As through-beam sensors, up to 600 mm can even be achieved. The robust stainless steel housing with specially sealed connection offers IP67 protection as standard. And since the sensors now work with visible red light, setup is child’s play compared to the earlier infrared light.

Further, the switching frequency has been increased and can now be set from 500 to 2,500Hz. This allows the evaluation electronics, for example, to reliably detect fine wires at high throughputs. Depending on the sensor version, the focus of the light spot is, for example, only 5mm in diameter at a distance of 10mm, ideal for detecting even small parts. All miniature sensors are equipped with robust, environmentally friendly PUR cables, can be assembled with different connections and operate in the range of -25 to +65°C.

Inductive sensors are now also available as miniature types with diameters of 3 and 4mm and housing lengths of only 12mm. These devices with a switching distance of 1mm offer particularly high repeat accuracy and precision in the smallest space. Sophisticated machine tools are the main area of application, since small sensors require fewer compromises in machine design. Even in miniature grippers, the small size of these sensors means that they will almost always fit in the right place to monitor the presence and position of small metallic parts, with counting and quality control, but without additional design costs.

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