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Calibrating hot formed workpieces

Calibration press automatically brings vehicle components into the final contour 

In order to maintain its competitive position, a globally active supplier to the automobile industry commissioned a press line for the middle of this year. The hot formed workpieces are brought into their installation ready final shape by means of cold state calibration. The planning and delivery of the calibration line was awarded to S. Dunkes. S. Dunkes, located in Kirchheim/Teck, not only enjoys an outstanding reputation as an innovative press manufacturer and competent forming specialist, but is also able to convince an increasing number of users worldwide with its specific engineering capabilities for the conceptual design and delivery of automated press plants.


Dunkes recommended the hydraulic  double column press, type HD 400, with a nominal force of 4000 kN for this calibration task. With table and ram dimensions of 850 x 750 mm, and an installation height of 1000 mm, the workspace provides sufficient room for the customers tools. These are brought into the workspace with roller tracks, positioned with stop rails, secured with four independently operating hydraulic clamp elements,  followed by securing and clamping the upper tool clamp plate with mobile clamping rails. The various tools are selected by the CNC control in accordance with the production programme. It also controls the spraying facility installed into the press frame. Spraying volume, spraying time and spraying interval are stored  for each part, and prevent surface damage by means of their controlled use.


The hold-down, which is configured for 200 kN, is arranged underneath the table bed. The ram can be retrofitted with an additional hydraulic ejector. At a ram speed of approximately 500 mm/s and a working speed of approximately 30 mm/s at max. press force, and a drive output of approximately 160 kW, sufficient reserves are available to economically adjust the press to the various tools. Off-centre loads are reliably transferred by the 8-unit ram guide across the entire stroke length. The adjustable flat ways ensure a guide accuracy of less than 0.03 mm – an extremely advantageous impact on the service life of the tools and the accuracy of the components.


The workpieces to be calibrated are fed into the press in the correct orientation on a multi-track steel slat conveyor. Using this linear feed track, a separator facility rotates the workpieces into the proper orientation and brings them into the correct retrieval position for component handling It consists of a transfer facility with three gripper pairs, which are designed for a workpiece weight of 10 kg. The grippers are quickly adjusted to the various workpiece sizes with quick-change adapters. With horizontal travel of 1000 mm and vertical travel of 160 mm, the workpieces are deposited in the calibration tool with a positioning accuracy of +/- 0.1 mm. After the calibration is completed, the transfer mechanism retrieves the parts from the tool and deposits them for downstream transportation on a slat conveyor installed on the opposite press side. In order to ensure collision-free operating sequences in the frequently confined and poor visibility conditions in the workspace, the transfer facility is programmed during set up with the help of a portable control panel.


All press motions, including those of the transfer facility, are programmable on a MP 370 Siemens display control with touch-screen. It also visualizes and monitors axis travel. Workpiece or tooling related defects are automatically indicated and stored. The individually configurable control can be used to implement add-on functions, such as tool and quality monitoring, as well as the integration of automation components. the resulting high requirements on safety and reliability are fulfilled by the Siemens S 7 control. The previously separately installed controls for automation tasks and for safety relevant functions are combined into a common system using " Safety Integrated". This significantly reduces the project planning effort and the installation of safety relevant facilities – a decisive time and cost advantage for the user. The associated press programmes are designed and programmed by Dukes, and subsequently supported at the customer with our in-house service staff.


The entire plant is secured by a safety fence with electrically monitored access doors. The compact design of the press facilitates unrestricted access to the supply lines and service locations in the safety zone. An automatically operated safety door installed on the front side provides an additional safety margin for the press space. Since spraying fluids are used in the press, the plant is protected by an oil collection pan as specified by the water management act.


The calibration line has been working to the customer's full satisfaction since the middle of this year. The total cycle time of 12 to 20 workpieces / minute, which depends on the component size, was attained after only a short period. The short implementation time was yet another aspect that positively impacted the user plans. The plant was taken into service after only 8 months from planning to delivery. Should the plant, which is employed in 3-shift operation, experience malfunctions, support can be requested from the manufacturer via the remote service function. But this communications device is also recommended to discuss on-site optimisation tasks with the Dunkes specialists.

Both pictures show the HD 400 hydraulic calibration press during final assembly. The slat conveyor for component feeding is shown on the right, the belt for component retrieval can be seen on the left.