Customized solution for doubling of production rate

Various components for exhaust systems used in cars and trucks are manufactured on the servo-transfer press. It produces not only complex, voluminous components with a large drawing depth, but also simple, smaller parts requiring high pressing force.

Tenneco already manufactures similar components today on mechanical and hydraulic transfer presses, but the aim of this new machine was to combine the advantages of the hydraulic press with those of a mechanical press – as far as technically possible – as an optimum for Tenneco’s range of parts.  This new press was developed based on the lessons learned from problems in the past.

The result is a pressing plant customized to meet Tenneco’s demands. Automation, press, and drawing cushion are designed for high yield, with a maximum available stroke of 500 mm. A smaller stroke can be achieved with a pendulum. The advantage of the servo-press is the enormous flexibility it has as a result of the freely programmable ram kinematics with which the ram speed can be set precisely according to the forming (drawing) process. After forming, the press accelerates to its maximum speed, taking appropriate account of a time frame for transport of the parts. As a result, the press can achieve optimum productivity, even with complex components.

It is also important to consider performance of the drawing cushion as counterpart of the press ram. With its freely programmable, hydraulic movement guide, this high-tech drawing cushion from Bosch Rexroth can be programmed for all necessary program characteristics, be it uncontrolled mode, degressive or progressive force progression, with or without pre-acceleration, or only as ejector. This drawing cushion is the optimum solution for the performance of the servo-transfer press from ANDRITZ Kaiser.

The complex, asymmetrical structure of the components that generate heavy eccentric loads on the press structure has already been mentioned. This particular challenge was resolved by the extraordinary stability and rigidity of the press frame.

In addition to the large-volume deep drawing parts, the press is also suitable for smaller, thick-walled components. With the pendulum, the stroke height can be set to the optimum for the respective die. Another highlight of this plant is the use of sandwich sheets. The coiling line from DREHER Automation has 2 coilers so that both metals strips can be conveyed to the press in parallel to one another. This process is state of the art nowadays in the exhaust systems sector in order to reduce noise emissions.

Highest precision, doubling of production, and reduced reject rate.

The machine’s high precision has proven to be a particularly positive aspect for the customer, Tenneco. As a result of the ram linear guides free from play and the related guiding accuracy, very small cutting gaps can be achieved, in the region of 2µ. Compared to the old hydraulic press, the yield could be almost doubled and the reject rate reduced by up to 25%, depending on the component.

The servo-curves are programmed in the proven ANDRITZ Kaiser curve generator integrated into the press control. Tenneco can use this to generate a suitable curve for each die and store it in the die data. The press is driven by 3 servo-torque motors and has an efficient energy management system. A combination of a rotatory energy storage device and a condenser buffer absorbs the energy generated when braking and passes it on to the intermediate circuit again during the working stroke. The advantage of this solution is that the transfer is also integrated into the intermediate circuit in terms of drive technology so that the energy stored can be used to return the press to a secure position in the event of a sudden power loss.

As the press plant had to be integrated into an existing machine hall, there were many obstacles to overcome. The roof had to be raised specially due to the size of the machine. And there were considerable challenges lower down as well because the pit is five meters deep. The press, stripped down to its component parts, could only be positioned safely at its new destination from above. One of the largest mobile cranes available in Germany was needed for this purpose.

In order to reduce the tooling times, the press has a semi-automatic die changing system with a tandem-type changing carriage; the dies weigh up to 25 tons.

A particular highlight is the very fast start-up curve for the overall plant, which was only achieved thanks to the collaboration of all concerned, such as the plant operating company, stamping plant engineering, press supplier, automation manufacturer, architect, logistics planner, and so on. Precision and productivity was always the main consideration throughout the entire concept.

Advantages of the new plant for customers

• Productivity almost doubled
• Reduction of scrap by up to 25%
• Batch sizes of 2,000 to 6000 parts, depending on the components concerned
• Stroke of 500 mm max.
• High flexibility due to freely programmable ram kinematics
• Use of sandwich sheets due to parallel transport
• Smallest cutting gap in the region of 2µ
• Efficient energy management system