Page 21 - MetalForming June 2009

typically restricted to the hydraulic overload safeguard, raising the moving bolster and hydraulic die-clamping sys- tems. All of these functions generally are supplied from a central hydraulic unit.
With transfer presses, additional hydraulic functions include engage- ment of the clutch between the press and transfer-drive systems, and the comprehensive system of scrap-ejec- tion flaps. In addition, hydraulics may drive various clamping and locking devices around the press. The most important function in mechanical presses—engaging and braking the slide drive system—is increasingly being accomplished via hydraulics. The use of hydraulics permits higher switching fre- quencies in single presses, and is more environmentally friendly in terms of noise and air pollution. The clutch and brake are supplied by a central hydraulic unit equipped with a cooling system. Also required: A dual-channel safety control with regulated damping facili- ty and pressure filtration to 10 μm.
The increased use of deep drawing with single-acting presses places strin- gent demands on the blankholding function and, therefore, the draw cush- ion in the press bed, particularly with large panel presses. Multiple-point bed cushions with pressure control capabil- ity then are only possible using a complex servo hydraulic system. This requires separate supply units with oil tank, pump outputs of approximately 150 kW and oil-flow rates of approximate- ly 1000 l/min. for the draw cushion.
Keeping PressesWell Lubricated
The complex lubrication systems used to supply the lubrication points of mechanical presses can be simplified by using valve blocks. The typical lubri- cation system comprises parallel-switch- ing progressive distributors. To allocate the required quantity of lubricant, the system includes volume controllers, dividers and similar elements. The flow of oil is monitored at the distributor blocks and, to ensure optimum operat- ing conditions, a control system regu- lates lubricant temperature within a narrow bandwidth, by using auxiliary
heating and cooling functions.
To maximize operating safety, com- plex production installations for met- alforming always include twin supply- unit elements, such as pumps and filters, so that if one element fails there is no need to interrupt production, as the second system cuts in automatically. Also, maintaining or exchanging the defective system does not interrupt production. In smaller presses, and in particular
bottom-drive knuckle-joint presses, central lubrication systems with multi- ple-circuit geared pumps find use. These systems continuously supply lubricant to as many as 20 main lubrication points. During the short swivel move- ments executed by the thrust elements and joints, a constant flow of lubricant is available even under varying resist- ance levels in the individual user and supply lines. MF
®
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Machining Components
F.E.A. Analysis
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(800) 558-6040 • superiordieset.com
• Full sheets 96” x 240”
• Stocked in A36, 4130 & 4340 • Grinding to 164” diagonal
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write no. 21 METALFORMING / JUNE 2009 19