Combination for innovation

Up to 200 complex wire-bending parts per minute, each featuring up to 20 bends, and production change at the press of a button. That’s the bar set by a new rotary transfer bending machine from Altena, Germany. For the first time, Schmale Maschinenbau GmbH has combined the benefits of two established bending processes and implemented around 90 servo drive axes in the tightest of spaces – using Siemens technology.
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Challenge

Highly dynamic, precise and flexible

Combination for innovation – at Schmale Maschinenbau in Altena, Germany, this was key in the new development of the highly productive and flexible bending machine, aptly named SPEEDMAX. A high-performance motion controller from Siemens coordinates the dynamic drive train dynamically, precisely and flexibly.

Every aspect is designed for maximum speed – from the programming to production and product changes. The new approach combines the benefits of freely programmable finger benders, known from flexible-use CNC-controlled wire-bending machines, with those of a fast transfer system for traditional, slider-based bending machines to achieve maximum output. The company has united both in a rotary transfer machine with 20 stations for the first time. The combination of finger benders and rotary positioning grippers also enables high degrees of freedom, such that the parts can be turned in almost any way and machined at various levels. The independent rotary transfer unit operates all the stations simultaneously in each cycle, enabling an output of up to 200 parts per minute.

With longer cycle times, several bends can be completed at each station, and parts can be stamped, joined or tray-loaded on the machine. The latter was one of the core objectives of the new development: Schmale Maschinenbau GmbH, a leading manufacturer of special wire-bending parts, wanted a flexible solution with a significantly higher output and, above all, the integration of the tray loading that was previously handled separately. In addition, the company wanted it to be possible to economically produce around 20 different part variants with varying batch sizes. Schmale Maschinenbau took on the challenge and, working with partners, developed a high-performance solution.

Solution

Servo drive train for flexibility and dynamics

The tough requirements could only be met with a high degree of automation. Electronic servo motors now power all moving machine components. The rotary transfer table, finger benders, and clamping grippers are all freely programmable. For flexible, fully automated operation of the ready-to-fit parts, some 90 servo axes are arranged and coordinated in the tightest of spaces.

Compact servo motors were (further) developed and designed for high speeds in order to achieve maximum dynamics in a minimum installation space during processing of wire up to four millimeters in diameter. In partnership with Siemens, they were connected to the scalable SINAMICS S120 drive/converter system. “This allows us to implement every drive solution cost-effectively,” says Sales Manager Andreas Goseberg.

SIMOTICS S-1FK servo motors are installed at all points that do not have these extreme requirements; two electronically interlinked servo motors, for example, ensure highly dynamic acceleration and braking of the rotary transfer unit. “To make sure there are no resonance issues, we implemented a special variant of the speed and torque coupling with the drive specialists from Siemens. At any speed, it ensures defined preloading of one axis relative to the others and thus smooth, well-balanced running,” says Johannes Graf, Head of Control Engineering at Schmale.

The digital DRIVE-CLiQ system bus for the Siemens drive components saves additional sensor modules in the control cabinet (SMC) and the motor parameters can be automatically read without errors via electronic name plates, thereby simplifying and speeding up commissioning and replacement.

Modular motion control – custom-scale drive performance
A SIMOTION D455-2 multi-axis controller expanded with 15 SINAMICS CU320-2 PN/DP control units acts as the primary controller, ensuring the perfect interplay of all the drive axes. In the electronic camming, all of the axes are coupled to a virtual main axis, which as the master specifies the machine speed. The individually adjustable coupling ensures the ideal coordination of all system components at any speed and enables fast, smooth movement and steady, well-balanced running.

The motion control system communicates with a fail-safe controller (F-CPU) in the form of the distributed SIMATIC ET200S I/O system via PROFINET using IRT (isochronous real time) communication and the PROFISAFE protocol. The F-CPU monitors elements such as the emergency-stop systems and access to the system’s secure area using light barriers. The control units of the drive line-up feature drive-related safety functions such as Safe Torque Off (STO) and Safe Stop (SS1), saving on additional safety hardware and wiring requirements.

Benefits

Convenient monitoring and control

At Schmale Maschinenbau, an essential requirement for such complex machines is having the simplest possible, most convenient graphic interface for operation using SIMATIC touch panels. The company modified and ported its established concept to the SPEEDMAX, maintaining its operation philosophy.

The HMI (human machine interface) system supports operators in creating and editing bending programs. They can focus on the workpiece and transfer dimensions and bending radii directly from the drawing to an image window – the SIMOTION system uses this information to calculate all the required motion data. In the process, it makes use of the tool data stored in a database. Existing programs can be loaded, duplicated, and easily modified. In addition, the option to show motion curves for related axes (clamping gripper/bending finger) simplifies programming. If a fault occurs, the operators can view the full operating instructions on the panel to quickly rectify the error.

Hugely increased productivity possible
At present, the system can produce an item with “just” twelve bends, but applies a mounting nail to each part. At the same time, output has been more than doubled compared to prior solutions. In addition, the integrated loading of finished parts in plastic trays saves a great deal of subsequent time, effort, and thus also costs.    

“Slider-based bending machines are in themselves considerably faster than CNC bending machines. The SPEEDMAX, however, is – depending on the task – two to three times as fast as a slider-based bending machine. The advantage of CNC machines compared to slider-based systems is fast tool changing. Thanks to its smart design, the SPEEDMAX offers just this advantage when changing products,” says Sales Manager Andreas Goseberg.


A principle that can be applied to other applications

Millions of manufactured bent parts prove that the principle works perfectly in practice. Word has spread to other industries: the German machine builder has already engineered a SPEEDMAX variant for wires and tubes eight to twelve millimeters in diameter, and is planning a further one for average diameters of four to eight millimeters. “Neither of them present extreme requirements with regard to moment of inertia and installation space, so we could consistently use the preferred standard versions of the SIMOTICS S motors from Siemens,” says Andreas Goseberg. Tape can also be processed on them, which will result in further new applications.

Output has been more than doubled compared to prior solutions.
References

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