Page 39 - MetalForming July/August 2009

Spring can
Pad spools (different size)
Pad
Pad
Nylon screw
Fig. 2—Spools of different lengths also should be a different size.
strip is not level, the parts may be pulled out of location.
10) Provide windows in the face of large stripper pads so that ball lock punches can be removed easily.
11) For material that is more than 0.045 in. thick, provide pad balancers to prevent damage to the die caused by pressure pads tipping during the start of a new coil of material into the die.
12) When a pressure pad will not balance on the stock in the work sta- tions, provide stock balancers to prevent tipping.
13) Do not locate springs over a stock balancer as they will provide no holddown force to the part being formed.
14) Remember that springs located half way between a pad balancer and the material only provide one-half the spring force on the stock material.
Next month we’ll examine the advantages and disadvantages of various stripper plate designs. MF
mounted improperly (Fig. 2). Advantages of using keepers:
• Increased rigidity and reduced tip-
ping due to more surface area,
which provides improved guiding; • A keeper that is correctly designed will not bend or deflect and cause jamming whereas stripper bolts
bend easily;
• Keepers provide more strength
under high stripping pressure whereas large strippers would require far too many stripper bolts; and
• Keepers are the best choice for long stripper plate travel due to better guiding.
Advantages of using spools:
• Reduced space required on the die
shoe as compared to keepers; and
• The round shape is readily machined reducing machining
costs.
4) Use spring cans around springs in
every pad that bottoms out.
5) Use spring retainers to hold
springs in the upper die if a pad is removed for service.
6) To get longer life from nitrogen cylinders, do not use the maximum pis- ton travel listed in the catalog—instead, use 85 percent of rated travel.
7) Do not preload nitrogen cylinders with the pad keepers. Provide extra travel (1⁄8 to 1⁄4 in. is common) on the keepers beyond full piston extension.
8) Make the pad travel slightly more
than the die work. This is required so the material does not move if there is pad bounce.
9) In progressive dies, all upper pres- sure pads that push stock lifters down as the die closes must have the same trav- el so that the strip and lifters are level as the parts locate in each station. If the
Not if you call Multipress, your one and only source for OEM parts supporting Denison and Multipress presses dating back to World War II.
We have a large inventory of hard-to-find repair parts for control valves, index tables and many other hydraulic components. We also have complete repair, rebuilding and testing facilities for valves, pumps, index tables, as well as entire presses.
Let us help keep your older equipment running like new. Call our parts specialist, Michael Schwartz at 614-228-0185, extension 238.
Replacement control valve, part no. C404,
in stock at Multipress
Columbus, Ohio sales@multipress.com www.multipress.com
Part no. C304, solenoid control valve, originally installed on a Denison bench press built in 1973.
www.metalformingmagazine.com
write no. 25
JULY/AUGUST 2009 37