Forming technology: Flywheel out – servo motor in

Hatebur Cold forming machine
The wire – on the right in the picture – is fed into the cold forming machine and formed. Hatebur is now relying on a direct drive from Siemens.

Hatebur now also offers its cold forming machine with a direct drive – instead of a conventional drive with flywheel. For this purpose, the company relies on a servo motor from Siemens and achieves a completely new flexibility in the forming process.

How are complex metal moulded parts, screw nuts or hose nozzles actually produced? For large quantities, they are usually not manufactured or cast by machining, but pressed into the desired shape. Steel – cold or heated – is formed in several stages with progressive tools and by using high pressing forces. For example, spark plug bodies and connecting parts for the automotive industry, or chain rollers for conveyor belts are also produced – almost without material loss.

When forming steel, enormous forces are engaged. So it is not surprising that the horizontal cold forming machine developed by the machine manufacturer Hatebur weighs impressive 60 tons. The machine body alone weighs 30 tons. This gives the machine the necessary stability and stiffness when the press carriage moves forward during the forming process with a maximum pressing force of 250 tons and rattles up to 180 workpieces per minute out of the machine. In the case of the raw material for the press called COLDmatic CM725, the experts speak of a "wire"; however, this can reach a stately diameter of two centimeters. The wire is pulled from a reel through a straightener into the forming machine. The sections cold sheared in the machine are grabbed by pliers and formed one after the other in the multi-stage tool of the machine.

Hatebur Umformmaschinen AG

Hatebur is a global developer and solution provider of machines, tools and processes for hot and cold forming. The company, based in Reinach, was founded in 1930 and is 100 percent family-owned. Around 300 employees at locations in Switzerland, Italy, China, Japan and Germany secure the Group's leading market position and technological leadership.

Significantly more flexible forming

Until now, Hatebur equipped its forming machine with a conventional drive. A rather small asynchronous motor set a large flywheel with a diameter of almost one meter and a weight of over 1000 kg in motion. This transmitted the power via a gearbox to gears and cam discs, which ensured the feed movement of the press carriage and the auxiliary drives such as ejectors and scissors. The speed of the engine was constant.
With the latest version of the horizontal press, the company, which has been family-owned since its foundation in 1930, has succeeded in an innovative further development: the traditional mechanical drive of the press carriage has been replaced by a servo motor. With a servo motor, acceleration, speed and the angular position of the motor shaft can be flexibly controlled. Andreas Maritz, Innovation Manager at Hatebur, sees clear advantages in the new technology: "We can now program the main drive as well as the existing servo drives of the wire feeder, the transverse transport and the pliers and flexibly coordinate all movements of the machine. This allows us to choose the optimal settings for each workpiece. For example, long parts can be transported slowly so that the machine grips them safely and no piece is lost or slips. Or, if necessary, we reshape a little slower in favor of tool life, but transport faster. This means that by adapting the kinematics as required, the process is improved with at least the same productivity."
Where previously the large flywheel provided the power for the forming, an impressive SIMOTICS T-1FW3 torque motor with an output of 500 kW and a torque of 8150 Nm is now enthroned. "Fortunately, the motor fit almost perfectly into the machine," says Maritz, "which allows us to offer our machines both with the previous drive and with a so-called direct drive without flywheel." The performance of the direct drive is comparable to that of a flywheel drive, but part of the kinetic energy must be used in the entire drive train. The resulting relatively small engine makes it possible to vary the speed in a targeted manner via a crankshaft revolution.

Easy to maintain thanks to less wear

We had been flirting with equipping our machines with a direct drive for some time and were also in contact with Siemens for this," recalls Maritz. When a long-standing customer from the surrounding area ordered another machine about two years ago, he was convinced by the new technology.

The customer, a supplier to the automotive industry, will also be pleased with the maintenance of the system: Numerous wear parts such as clutch, brakes or V-belts are eliminated, which makes the machine significantly less maintenance intensive. Maritz explains: "If we reshape more slowly, the tools have to be replaced less often. Stable, quiet transport prevents a workpiece from entering the cavity at an angle." The fact that the flywheel no longer has to be set in motion and braked saves time in daily operation, for example when changing tools.

Global success with Siemens

The thick cables make it clear that large currents – up to 1430 A – flow here to operate the enormous machine with a forming work of up to 18 kJ. The energy for the forming process, which used to be stored in the flywheel, must now be provided differently. Air-cooled capacitors ensure that no excessive power fluctuations burden the grid. They are charged with mains power, store the energy until it is formed again and thus smooth the power curve. Thanks to this almost constant connected load, the operator does not incur high costs for large power peaks.

It is no coincidence that Hatebur, which employs around 300 people worldwide, chose Siemens for this project. "We use Siemens controllers as standard," explains electrical engineer Pascal Schwarz, who co-developed the direct drive control system based on a SIMATIC S7-1500TF. "Since we sell our machines around the globe, we also appreciate the worldwide service provided by Siemens." The fact that Siemens supplied all drive components – control cabinet, motor and press control – ex works was another plus and, last but not least, the price was right.

Efficient automation with the Simatic SimaPress Servo Standard

For efficient automation, Siemens has developed the SIMATIC SimaPress Servo Standard with prefabricated software modules especially for servo presses with a SIMATIC controller. "We use our own software for our presses, which has been developed over the years, and use parts of the SimaPress Servo standard to control the direct drive," explains Schwarz. Schwarz was able to contact the Siemens Application Center APC at any time with his questions.

Soon the machine will be delivered to the customer, connected to the power grid and start production – plug & play. Maritz and his team are pleased that the new development is being used under real production conditions and see great potential for direct drive in forming technology.

Technology in brief

With the technology objects in the SIMATIC controller, servo technology makes it possible to precisely control the SIMOTICS T-1FW3 motor torque motor and thus dynamically adapt the pressing movement to the workpiece. Not as in the past the king shaft, to which all movements in the machine were coupled, but a virtual guide axis sets the clock to which all servo motors in the machine synchronize.