Safety Safely and Unmannedly Load and Unload Machine Tools

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K.A. Schmersal GmbH & Co. KG

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Updating machine safety was the goal of Wassermann Technologie. The company has revised its storage and loading system for clamping pallets, which allows for automated loading and unloading of machine tools. The safety technology can now be installed via plug-and-play.

Wassermann Technologie, based in Eichenzell near Fulda/Germany, offers a solution for retrofitting older machine tools with automated loading and unloading capabilities. Their Work-S series provides advanced storage and loading systems designed for clamping pallets, which seamlessly dock with the machine tool, enhancing efficiency and productivity.

Modular system automation of machine tools

About 25 years ago, Wassermann, then known as HPI, started developing tool changers and has since been supplying reputable OEMs such as DMG Mori, Index-Werke, and many more with tool magazines and entire tool change systems. The automation of machine tools has since become a distinct business area. Leading manufacturers of machine tools have included the terminals—as they are called at Wassermann—in their range, offering factory automation. Wassermann designs each terminal based on a modular system.

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Unmanned shift even with batch size one

The user of a Work-S-Terminal can clamp the workpiece, weighing up to 800 kilograms, or several smaller workpieces, onto a clamping pallet at an integrated setup station. From there, the pallet is transported to the machining center, and all required job data (pallet, tools, clamping devices, NC program, etc.) are transferred via a data bus, and the pallet is processed accordingly. The connection of the terminal to common control systems such as Procam or Soflex ensures a continuous flow of information.

Once the processing is complete, the pallet can be automatically unloaded or temporarily stored in a one or up to six-level pallet storage. This enables the machine operator to run complete unmanned and weekend shifts. This applies not only to batch production but also to batch size one per workpiece.

Designers revise safety interlock

In the latest generation of Work-S stations, Wassermann's designers have revised the machine safety, starting with the level of safety switching devices. Michael Jestädt, Deputy Head of Design and Electrical at Wassermann Technologie, says, "The setup station is secured with a swiveling double door because a wide opening angle is needed for loading. Due to design and space constraints, the safety interlock was mounted at the bottom of the protective door, some distance from the door handles. This strains the structure, can lead to warping, and is also not ideal visually. Therefore, we looked for a better solution."

The safety interlock of the AZM40 series from Schmersal can be installed at the height of the door handles and in close proximity to them, without the handling of the pallets or the centering of the workpieces being affected by interference contours. Jestädt explains, "Now, the force when opening the protective door is applied exactly where the lock with the interlock is located."

Plug-and-play for safety bus technology

On this occasion, Wassermann also opted for an optimization at the level of safety-oriented signals. The Work-S systems are controlled via a Beckhoff Twincat3, and Schmersal offers an up-to-date version of the Safety Fieldbox for this purpose—with interfaces for Ethernet/IP and Ethercat. This opened the door for Wassermann to safety bus technology and to the flexible installation of safety switching devices according to the plug-and-play concept.

The Safety Fieldbox allows the on-site connection of up to eight safety switching devices. In addition to safety interlocks, sensors, and light curtains, operating panels and emergency stop buttons, for example, can also be easily integrated into the safety circuit simply by connecting the eight-pin M12 connector. An integrated digital input allows for the evaluation of diagnostic signals. Thus, non-safety-oriented signals are also collected and transmitted.

Quickly installed for flexible use

This type of connection brings practical benefits: The user saves costs because not every single device needs to be equipped with a bus interface. They gain flexibility because they can integrate various types of safety switching devices, and they also save time because the installation is simple. "The first time you might still have questions, but by the third time, all the safety components are installed very quickly," describes Jestädt. Additionally, with the Ethercat variant for the Beckhoff control, there is the advantage that remote maintenance can be easily implemented.

Safety Fieldbox for two machine tools

In a current project, Wassermann built a Work-S-300-4 terminal that allows the automated loading and unloading of two side-by-side machine tools. The same Safety Fieldbox is used as in the terminals for a single machine.

As part of the revision of the Work-S series, Wassermann also made a change at the safety level. Contrary sliding vertical doors are installed at the physical interface of the terminal to the machine or machines. They are usually open and are only closed during maintenance work on the terminal or the machine. Three safety sensors from the RSS36 series by Schmersal monitor the position of the protective doors and are also connected to the Safety Fieldbox.

Currently, Wassermann Technologie GmbH is working on additional terminal variants. A linear, rather than carousel-type, loading and unloading system has already been implemented, which can supply up to six machines via a robot. In addition to the workpiece change terminals, Wassermann also plans automated change systems for up to about 700 tools, which are also suitable for retrofitting on existing machines.