Automate The Handling Of Bent Wire Parts With Grippers

2023 Author : Hannah Pearcy | [email protected] . Last modified: 2023-05-24 11:12

Technical springs and bent parts are the focus of Bahner und Schäfer GmbH. The spring production is equipped with modern machines and systems, including a modern CNC-controlled bending center. Despite the high technological standard and degree of automation in the company, some final processes in the bending center were still carried out manually in the past. When finishing the bent wire parts, for example, a cutting edge separated the product from the raw wire after the bending process. Then it fell into a big box over a slide. In order to reduce the internal stresses of the bent parts that occurred during the process, a large part of the products had to be subjected to a subsequent heat treatment.

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Bent parts laboriously separated by hand

However, a homogeneous material structure could only be achieved after the heat treatment if the parts were individually positioned in the furnace. The separation and positioning were laborious by hand, required a great deal of time for the worker and represented a not inconsiderable cost factor.

The quality of the bent parts also suffered because the individual workpieces got caught and deformed when they were removed and separated from the box. Another production step was also carried out by hand: certain parts had to be chamfered on the edges, which had a negative impact on production costs.

In order to further develop the production of bent parts, Bahner und Schäfer GmbH had discussed together with the Chemnitzer Maschinen- und Anlagenbau eV (ICM) how an automation solution could help the company reduce costs, increase productivity and make its employees more efficient to use or to free from the dreary activity of manual separation.

With ICM as a project partner, Bahner and Schäfer had brought in a specialist. The ICM is a private, non-profit, application-oriented research facility (industrial research facility) whose primary goal is to open up new technical and technological opportunities for SMEs. They have many years of experience and a high level of expertise.

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The challenge for the ICM was to design a system or system that can be integrated into the existing processes, is easy to use and has an acceptable amortization. In addition to pure robotics, important issues such as flexible gripper systems, supply and discharge of material and energy, and machine safety had to be clarified in a successful introduction.

Now a robot separates the parts

In addition to a specially designed wire-end processing machine that automatically fastens the parts, the ICM relied on a flexible robot cell for the solution for an automated separation process of the bent components. An industrial robot is now used within a protective fence, which picks up the bent parts from the wire bending machine and hangs them in a device in a defined position or stores them in a controlled manner. The suspension register serves as an intermediate station before further processing in order to store all bent parts that can be hung without getting caught.

The handling of the application consists of an XY linear axis system (2000 mm x 3000 mm), which consists of a double tandem and a single axis with a follower and a six-axis Kawasaki robot RS010L. The axis portal enables the robot to move on a 7th and 8th axis.

Versatile gripper required

Various grippers are available to the robot for handling the various bent parts. The robot uses a large pool of available grippers, the so-called gripper station. Here he can select the right gripper for the respective task.

Gripper

Criteria for choosing the right gripper

Robot-based handling

Handle in the nest: Filling in the clean room with a safe grip

The ICM selected hybrid grippers from the gripper specialist Zimmer Group from Rheinau as gripping tools. "We needed a high gripping force because the parts have to be held securely while driving," explains Marcel Ott, one of the ICM project managers, about his decision. In addition to a large stroke, the current position of the gripper was important for the process, for example to recognize whether the wire was gripped exactly. The integrated measuring system does this. The supplied IO-Link technology transfers the measurement data, such as status data or positioning data. Ott: "We used Zimmer's tool changing system (WWR63F) to be able to handle larger workpieces in the future."

To the website of Zimmer Group

The result of the entire system can now be seen: The management of Bahner und Schäfer GmbH is enthusiastic and the project partner ICM is also satisfied with its own implementation. The fast automated handling significantly increases productivity. The system is designed so that the operator can set up the robot system for each new part within 15 minutes. Retrofitting is possible by using recipes in seconds. Alexander Reinhold, responsible for quality assurance at Bahner and Schäfer, was impressed by the significant increase in quality in the production of bent parts.

Due to the mechanical chamfering, it is now possible to work even more precisely and the deformations on the bent parts caused by the hooking during manual removal from the box are a thing of the past.

Additional information on the subject of success with axis alignment

The project managers at ICM had to face several challenges during the implementation of the project. In addition to the very complex assembly of the robot cell on site, there were also initial difficulties in the production itself. It turned out, for example, that the bent part or the raw wire changed its position slightly each time it was handled by the cutting process.

However, since the gripper remained rigidly unchanged at the moment it was cut, the workpiece had bent a bit with each cut. "In order to successfully counteract this process, we have mounted an axis compensation (model AR63P) on the last axis of the robot, which is softened at the moment of cutting (pneumatic pressure) and only after the complete cut by precisely timed pneumatic control of the locking piston returns to its usual rigidity”, Thomas Schröder, technical support & sales of the gripper manufacturer Zimmer Group, describes the quick and easy solution to this problem.

Further automation is to follow

In addition, the monotonous activity of separating by hand has been eliminated for the worker. With increased motivation, he can take on more valuable tasks in the company in the future. For Reinhold, however, the system is only the first step in automation. More are to follow. The next phase could be, for example, the expansion of the system so that in the future even more complex workpieces or bent parts can be processed.