Technical milestone: Schuler Group produces world¡¯s largest counterblow hammer

June 3, 2008. M¨¹ller Weingarten, a subsidiary of the Schuler Group, produces the world¡¯s largest counterblow hammer. The customer will use the line mainly for the production of crankshafts and flanges, for commercial vehicles for example.
    
Whether for container ships, locomotives, commercial vehicles or planes ¨C almost all transport vehicles operating in global logistic networks rely heavily on large forged parts. There has therefore been a corresponding rise in demand for large forging machines with high press forces and forming energy. Especially when it comes to large forged parts, the counterblow hammer represents an economic and technically extremely attractive alternative to forging presses. In combination with modern technology, it is possible to assemble modern and cost-efficient forging lines with a counterblow hammer. The flexibility of such lines also guarantees maximum investment safety.
   

The principle of the counterblow hammer is that two forging hammers ¨C known as ram hammers ¨C with similar masses are moved in opposing directions, reaching their optimum speed at the exact moment of forming. As the opposing directions of the hammers almost balance out the impact forces, little of the force is led into the hammer foundation. Consequently, this can be made smaller than for drop hammers. The benefits of the principle are its high forming speed and high forming energy, guaranteeing high precision for the production of large and complex forged parts. Further benefits include high availability and low maintenance needs.

There are two basic types of counterblow hammers. In the case of hydraulically driven counterblow hammers, a hydraulic system moves the two hammers against each other. The hydraulic hammer works independently of a compressed air system and can be regulated more precisely than pneumatically driven hammers. However, the maximum forming energy is limited to 400 kJ due to the load limitations of the hydraulic system. The available hydraulic components also limit the construction size. Pneumatically driven counterblow hammers on the other hand, such as the world¡¯s largest counterblow hammer currently being built by the Schuler Group, provide a maximum forming energy of up to 1,400 kJ. This corresponds approximately to the performance of a forming press with a force of 54,000 tons.
   In both processes, the drive is delivered via the upper hammer. In pneumatic drive systems, the upper hammer and drive piston are formed from a single piece, so that the compressed air from the control cylinder acts directly on the upper hammer. The expansion principle and the use of dry-running compressors, which avoid the need to cool the heated compressed air, improve the economic efficiency of hammer operation. The servo-hydraulically operated valves used to regulate pressure guarantee high operating reliability.

A hydraulic clutch system transfers the movement of the upper hammer to the lower hammer, so that both hammers have synchronized opposing movements. The clutch consists of two pistons acting on the upper hammer, which pressurize the piston acting on the lower hammer via an oil column during the blow stroke. The pistons are hinged directly on the hammers without any elastic interlinks. The clutch cylinder under the lower hammer is equipped with a hydraulic brake. This brakes the lower hammer during the return stroke before reaching its final position, where it is gently cushioned by buffers. This simple and robust design requires little maintenance and guarantees high hammer availability. With regard to total cost, therefore, it offers clear advantages over more complex forging presses.

 

 Broad part spectrum and high flexibility

In contrast to other hammer designs, the greatest external dimension of the hammers in seam direction can be used as die support for the upper and lower hammers. This enables the use of very long and overlaying dies, offering benefits especially for the production of long forged parts ¨C such as truck front axles and crankshafts. Due to its favorable design with almost equal masses, the die-to-die blow force of the hammer is extremely high. This allows economic production of large forging pieces with thin walls requiring high forming forces, e.g. turbine paddles. The eccentric arrangement of the clutch pistons on the hammers also enables a well-defined positioning of the hammers on the guidance holder. In contrast to other hammer designs, over-high and heavy dies can also be mounted.

The uprights are generally welded assemblies and can be supplied as 2-upright or 4-upright solutions. The outside mounted guidance of the ram hammers guarantees exact hammer movement and thus high-quality forging results.

 Modern control technology

The MW-FCS (MW Forge Control System) enables users to utilize all the line¡¯s operating modes: such as set-up, die positioning, manual or automatic operation. Users can select complete blow programs ¨C with individual settings for the number of blows, energy per blow and pauses between blows ¨C and then store them separately for each die.

 

The Schuler Group offers pneumatically driven counterblow hammers in the range from 160 kJ to 1,400 kJ. A wide selection of available sizes ensures that customers find the size exactly suited to their particular needs. However, it is also possible to order complete modern forging lines, including partial automation, based on counterblow hammer technology.