High-level automation in sensor manufacturing - parts

A company that wants to economically and efficiently manufacture products in high-wage countries such as Switzerland must explore the possibilities of automating traditionally manual processes.

In the photo above (left to right): Robert Betschi, Martin Kluge (SCHUNK), Michael Rusch (SCHUNK), Florian Wernli, Bruno Tallmann, Ozel Kadir, Jonas Noller.

"We are perfectionists. Eighty percent is not enough for us," explains the philosophy of his team Robert Betschi, head of tooling at KELLER AG.

KELLER AG is known worldwide for its high-precision pressure sensors. The company applies the same high quality standards to its own production systems.

The project goal was clearly defined: To automate the process of cleaning, processing, and testing membrane housings for pressure sensors. Previously, all these stages were performed manually at manual workstations.

"This work is so monotonous that it is practically impossible to find employees to perform it," explains project manager Florian Wernli. The automated process had to ensure a verifiable and consistently high level of quality regardless of the experience and productivity of employees on any given day. In this project, the devil was in the details. Previously, all stages such as visual and technical inspection of parts, cleaning of parts, embossing, or checking embossing punches were performed by experienced employees. For each sub-stage, it was crucial to find or develop suitable systems that would ensure process stability and high-quality results. Four types of sensors were selected at the first stage, and in the medium term, up to 12 types are planned to be automated. The automated system combines advanced machine vision sensor technology and deep learning, demonstrating the high level at which the company operates. Ultimately, the company required a reliable method to detect and classify even the smallest deviations to ship only verified parts that meet quality standards to customers. This is important because much depends on the flawless operation of KELLER pressure sensors in the aerospace, oil and gas, water management, and automotive industries, including human lives: KELLER sensors monitor cabin pressure in airplanes, ensure smooth switching between natural gas and gasoline in bi-fuel vehicles, and serve as reference sensors in laboratory equipment.

The testing setup demonstrates high precision.

Project manager Florian Wernli immersed himself in the topic and thoroughly studied numerous aspects of the fully automated production and inspection module. "Before installation, the SCHUNK X-axes were tested for accuracy on a test rig with a measuring device. Now we know that the axes operate quickly and very precisely. We had no micrometer of play in the test application," he says, highly appreciating the interaction of the axes with Beckhoff motors ordered by KELLER AG. "Sometimes we work at speeds of 1000 mm/s, which requires high precision." Ultimately, the team chose a comprehensive partnership with SCHUNK not only because of proven high-quality standards but also due to the wide product range. "It was important for us that the number of suppliers did not become unmanageable. Therefore, we looked for a supplier who produces not only linear axes but also rotary modules, grippers, and rotary transfer devices at the quality level we strive for in the system as a whole," Wernli continues.

Axial system

Reliable and precise axis systems.

The automated system is equipped with a total of nine electric linear modules from the SCHUNK Beta and SCHUNK Delta series, which provide reliable, fast, and precise transport of up to 20 workpiece holders, each containing up to 380 parts. The spindle-driven linear modules used by KELLER AG deliver high drive forces up to 12,000 N in the maximum available size. They achieve travel speeds up to 2.5 m/s and high repeat accuracy of +/- 0.03 mm.

Transfer system

In accordance with the requirements of KELLER company, the modules are driven by a Beckhoff servo motor, which is connected to the axis via a flange and coupling or, in some cases, an angular gear. To increase the reliability and service life of the linear modules, specially attached plastic covers protect the guides and drive elements from contamination. Both series feature a robust design combined with high speed, ensuring short cycle times and high repeat accuracy. The double profiled guide gives the Delta series modules exceptional rigidity, so even heavy loads can be moved with maximum precision. Highly efficient Pick & Place units, cross carriages, rotary gripper modules, gantry systems, or complete functional modules can be created from the linear range of modules with minimal design and assembly effort. Even multi-axis systems can be implemented exclusively using standard components.

One striking example of application is the warehouse lift, which combines two Beta 40 linear modules 1400 mm long with synchronous drive as movement axes in the Y direction and a robust Beta 60 linear module in the Z direction. The axis system is used to move the pneumatic rotary device SCHUNK SRU-plus 40, to which a Beta 40 linear module is attached for movement in the X direction. Using the movement system, fully loaded pallets with part holders can be taken out of the warehouse, rotated 180°, and placed in the warehouse for assembly. From there, components are individually extracted by robots and directed to initial leak testing.

Storage lift

The second movement system is used for transporting parts after cleaning. It consists of a robust Delta 110 linear module 1115 mm long on the base (Y axis). This module is used to move a vertically mounted Beta 60 linear axis, which in turn moves the compact SCHUNK ELS rod axis. The rod axis is used for the actual processing of parts in the X direction and has the advantage that only the slider moves, like a telescope. Finally, the third axis system for part processing and punch stamping combines two synchronously driven Beta 40 on the floor with Delta 110 and three ELS rod axes.

Working with seals

Impressive technical support.

The KELLER AG team was impressed that the standard SCHUNK range includes all possible types of drives, from spindle drives to high-dynamic linear motor drives with fine gradation of various sizes. In addition, digital services facilitate the selection and design of components. However, by unanimous opinion of the team, the experience of SCHUNK gripping systems specialists is the most important factor. For example, Florian Wernli turned to SCHUNK for specific advice on the design of motors and linear modules.

"Martin Kluge and Michael Rusch, our contacts at SCHUNK in Switzerland, were able to tell us exactly what torque the motors should have or which spindle pitch is best suited to achieve a certain speed," says Wernli. "Since we plan to produce up to twelve types of sensors, there is never just one influencing factor, but a wide range of parameters to explore." It was very important for the team that the components are not always pushed to the limit, so they operate reliably and have a long service life.

"We want to use the automated system for ten years, so we also designed components with this requirement in mind," says Robert Betschi. In addition, the team wants to minimize manual adjustment.

Tray handling

Cleaning station

Combination of rotary/turning module.

In addition to linear systems, the sealed cleaning station deserves special attention when it comes to part processing: Two pneumatic rotary modules SCHUNK SRU-plus, which rotate the gripped parts by 90°/180°, were combined with a miniature SCHUNK ERD rotary module with electric drive for rotating parts. The rotary module has two integrated air channels and is also supplied with four electrical feedthrough channels and an SIL2-certified absolute travel measurement system. The electric rotary module is driven by a brushless synchronous motor with permanent magnet excitation. Its special geometry ensures high dynamics and acceleration. In addition, pneumatic drives connected to the module, such as pneumatic grippers used by KELLER AG, can be quickly actuated thanks to optimized air supply channels. These two factors together ensure short cycle times and high productivity. For moving parts on the Delta 110 linear axis, a combination of rotary/turning module can be used.

Cleaning cabin

Flexibility for custom solutions.

The KELLER AG team pays tribute to SCHUNK for making several individual solutions possible without unnecessary red tape. For example, the cleaning station is equipped with a SCHUNK servo drive, which was specially developed for Beckhoff controllers. "SCHUNK created a configuration file specifically for us and was able to guarantee in advance that the servo motor would work with Beckhoff controllers.

"We imported the file, and it worked immediately," recalls Kadir Ozel, responsible for programming in the project. "Overall, the axes were easy to control, and the inertia-to-drive ratio was very well thought out."

Martin Kluge, CEO of SCHUNK Intec AG in Switzerland, sees great benefits for users, especially when it comes to the compatibility of SCHUNK electrical components: "Beckhoff, Bosch, and Siemens are standard for SCHUNK. In Switzerland, in particular, we face a particularly high level of automation, as well as diverse types of automation. For such customers, SCHUNK often allows combinations with products from other drive manufacturers, including products that are used much less frequently. As a rule, we then develop and calculate the optimal motor parameters based on our experience and compare motor manufacturers," explains Kluge.

Weld seam inspection

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