Press automation for the forging industry

A German company named Automatic-Systeme Dreher GmbH is specialized in meeting these new requirements. This owner-operated company is working in the field of press automation for more than 45 years. The Hidden Champion for press automation employs about 200 people at their location near Stuttgart.

The field of forging represents the most challenging field of activity within the entire product range of Dreher. This area differentiates fundamentally from others like sheet metal forming for instance. There are high requirements for the automation due to environmental factors as the technical equipment is extremely stressed by external factors such as extreme heat, aggressive oil, greasing lubrication and other negative emissions.

Dreher developed solutions to solve these problems in order to respond to resulting demands.

The main purpose is to attain an ideal cycle time for the requested product. Simultaneously a safe production including a high availability of the system has to be ensured. Beside the handling task in the press also other processes such as parts feeding and tool cooling have an important role. After the consideration of all influencing factors a process-optimized solution can be developed in common with the customer.

The scope of Dreher is divided into three core interests:

1. Feeding of the parts

2. Handling the parts in the press

3. Greasing and cooling of the tools

Feeding of the parts

Different press designs and the diversity of preliminary processes require a variety of the part feeding.

Moreover, the design depends strongly on the requirement concerning flexibility and high stroke rates. In this case, feeding with a robot is the most flexible alternative. Additional processes such as roughing-down and channeling off parts being “too hot” or “too cold” can easily be integrated.

By achieving a high stroke frequency a robot attains its limits. Meeting this problem Dreher has developed a special feeding system. Depending on the design this equipment is able to channel off “too hot” or “too cold” parts and to feed horizontal as well as vertical parts.

Parts handling across the press

The main task of part handling is not only the feeding of the parts on the right time in the correct position but also the right transport position across the tool. The more sophisticated the design of a tool is the more demanding is the challenge for the automation company.

Fundamentally, two alternatives concerning the transport of the pieces across the press exist:

1. Robot technology

2. Forging transfer system (walking beam system)

Robot technology

Robots guarantee the most flexible manner to handle forged parts, smooth rotating and turning of the parts. The application is found mainly in case of small and medium quantities, as there is a quick retooling and high flexibility required.

Forging transfer system (walking beam system)

If production rate increase due to multi-stage forging processes the robot technology quickly reaches its limits. To meet this problem Dreher developed a walking beam transfer unit which has been designed especially for the application in forging.

In homogenous conditions the walking beam transfer guarantees a steady quality of the work pieces. The MAB-technology (Modular-Automation-Kit, consisting of 8 basic frame-sizes) allows to cover the complete range of application concerning cycle time, parts weight and part size.

In this context Dreher rely on linear motion and separated drive technology enabling asynchrony motion sequences in closing and lifting motion at any time. The high-dynamic servo drives are designed for the application needs and therefore guarantee an optimal output as well as a high availability.

In the forging area the drive units of the walking beam transfer are principally attached on the outside of the press columns in order to ensure the maximum distance to negative emissions (e.g. dirt, heat, aggressive greasing lubrication) inside the press. Despite this fact the drive units are manufactured to be completely closed and sealed to avoid an infiltration of remaining emissions.

According to the application the transfer can be manufactured either in a one-sided or a two-sided version.

Greasing and cooling of the tool

Especially in forging greasing and cooling of the tools have an important role. Not only to protect the tools from wear and tear but also to ensure a constant quality of the finished parts. It is a matter of fact that the permanent action of heat of the work pieces can easily have a negative impact on the tools.

As a general rule it is important to observe a reasonable spraying dose – a lot helps a lot does not apply in this case.

For this reason Dreher collaborates with notable specialists in this field. Spray systems are designed according to the application to be finally integrated into the whole system. For example, Dreher developed a possibility to realize spraying by an additional axis via spray arm, running in from the backside into the open press room. A further possibility is the integration of the spray unit into the transfer rails. Generally, the choice for an optimal spraying depends strongly on the work pieces and the available space.

Example of a forging transfer unit

Automatic-Systeme Dreher GmbH is not only a well-known manufacturer for press automation in the forging area in Europe but Dreher also delivers automation equipment across the globe. By means of the following example of a forging transfer (size 5) Dreher shows the technical layout of such an automation equipment. The automation has been designed for an existing 20.000kN Manzoni press. During transfer retrofit the control system of the press was also modernized by Dreher.

Scale of project

1. Parts feed via feeder

2. Forging transfer size 5

3. Protection device

4. Control system transfer

5. Control system press

Sequence description

The displayed forging transfer is used for a 3-axes transport of work pieces (closing/gripping, lifting, feeding, lowering, opening, return) across a sequence of processing stations in the press. The transfer takes over unmachined forged parts being fed from the oven via slide and pick up station (parts feed via feeder). With the help of grippers mounted on the walking beams the forged parts are transported across the different tool stages until the end of line conveyor (deposition station). Therefore, the press and transfer motion have to be synchronized.

The automation is designed as a modular system of four closing-lifting drives being mounted at the press columns. Due to a closed housing the mechanical system is completely protected from harmful emissions. At the in-feeding side two feed drives assembled in protective housing are integrated into the gripper rails (walking beams with grippers).

The construction as described here guarantees an easy assembly as well as good accessibility for service and maintenance purposes. As it is effectively independent of the press configuration, furthermore, it has no effect on the space in the tool room. Besides, this design enables an easy retrofit at existing mechanical or hydraulic presses. The basic requirement is a sufficient size of the presses'' side window in order to guide the gripper rails through the window without tool collision during closed press.

In addition, the described layout makes an easy back-out of the gripper rails out of the tool room possible. This results in better accessibility for tool change and maintenance work in the presses'' tool room. Therefore, the couplings of the gripper rails have to be opened and closed manually. An automatic rail coupling can also be considered. For the possibility of an easy and safe gripper rail handling outside, the rail can be stored on a slide table.

The transfer motion is regulated by the principle of rack and pinion. The ball-bearing of all mobile components guarantee low friction value and high dynamics. The movements are guided via low-maintenance, high accuracy via pre-tended linear guidance and lifetime.

The transfer movements are controlled by CNC-axes. The drive takes place via low- maintenance digital rotary current servo drives. In the field of control systems Dreher collaborate closely with Siemens and therefore use Simotion D for their transfer systems. The control of the motion sequences takes place via programmable geometric function according to a higher polynomial calculation. The PLC control system is realized with the Simatic S7 317F (integrated safety functions).

Part of the Dreher standard control package is also the safe reduction of the drive speed in case of an open protection circle. In manual mode the movements of the press and the transfer system can be run in tipping mode via mobile panel. This function simplifies the set-up of the tools. Thus, it can be tested directly at the tool while the protection device is open before changing to automatic mode.

The visualization of the system occurs via Comfort Panel TP 1500 made by Siemens including WINCC flexible and data administration for 200 tool sets. The panel is integrated in a fixed operation desk on the operation side of the press.