Page 19 - MetalForming February 2013
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 press, 600 tons of steel and copper were removed and assigned for internal recy- cling. Only the press bolsters, drives and foundations were left alone.
In the retrofitted press line, the press rams attach to the shaft with a 30-deg. offset from each ram to the next. The CompactTransfer system is synchronized with the movements of the press rams in real time. It can thus work with a minimum amount of maneuvering space, and optimizing stroke rate.
One of the specifications for the VW modernization project was systematic standardization, to facilitate mainte- nance and troubleshooting. Presses from various manufacturers and the respective diverse control systems were to be visualized on a uniform surface. Accordingly, the higher-level control system and the safety controller were to be designed consistently and trans- parently.
A Space-Saving Transfer Solution
The comprehensive transfer-automa- tion concept combines a blank feeder with a fully automatic tool-change sys- tem, the CompactTransfer system, and standard robots at the end of the press line. Programming the motion curves, Strothmann used Siemens press-sim- ulation software to determine the most efficient and safe paths. The theoretical maximum acceleration is 25 m/sec.2 for the horizontal axis and 15 m/sec.2
A key enabler of VW’s new production system is highly dynamic press-automa- tion technology, including Strothmann CompactTransfer crossbar systems designed to increase throughput by 20 to 30 percent over previous technology.
for the vertical axis. In operation, the system accelerates by 20 m/sec.2 (hor- izontal axis) and 10 m/sec.2 (vertical axis). Retrofitting the CompactTransfer system proved to be a simple and fast process for VW. It was able to exchange a complete module within a few hours by using the existing drill pattern on the press frames. In keeping with the drive for standardization and uncomplicat- ed maintenance, only standard parts were used for the linear-motion bear- ings and drives. And, as specified by the customer, Strothmann installed Siemens drives for the particularly highly demanding tasks.
In comparison with articulated-arm systems, the solution therefore offers a range of advantages: the linear tech- nology used for carrying out the com- plex and long transfer paths is sim- pler and more transparent for the operator; orientation stations are not required; and the drives are positioned where they cannot be destroyed by the dies.
Setup time also has been signifi- cantly reduced through automation. Strothmann fitted the die-change tables with front holding frames. Now, whenever the press line needs to be set up for different parts, the Compact- Transfer can simply place the cross- bar in the bracket so that it is removed from the press line along with the dies. The operator can then loosen the quick-release skewers on the crossbar and exchange the tooling.
Blank loading and End of Line
The blanks are carted in front of the press line on Strothmann Round- Tracks—a floor-rail system designed for transporting heavy goods. The rails are recessed to sit nearly flush with the floor, and, due to their reportedly extremely low rolling resistance (0.01 friction coefficient), RoundTrack sys- tems require relatively little energy.
Two feeders (Strothmann SRLM- 2/120 models) unload the blank trol- leys at a combined 18 strokes/min. The trolleys feature lifting apparatus to mechanically adjust the stack height. Double blanks are automati- cally detected and discarded, and then the sheets are washed and lubri- cated. An indexed conveyor then transports blanks to the press as a set of four line cameras monitors their positions. A vision system analyzes the data and, based on the results, directs two centering robots to correct blank position.
At the end of the line, an out-feed conveyor carries parts away from the press line where awaiting parts- removal robots orient the parts for the operator. The operator then loads the parts into customized containers that locate them in the correct ergonomic position for unloading at VW assembly lines. MF
Article provided by Strothmann, with U.S. sales based in Marietta, GA: 770/424-4141; www.strothmann.com.
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