Page 39 - MetalForming September 2010

Number of Cycles vs. Punch Design
180,000 150,000 120,000
90,000 60,000 30,000
0
148,031 pcs. (8-12-09)
x x x x x x x xx x x x
Standard punch Current baseline
removed after
31,000 cycles
due to burr Dual head punch
Standard punch x Target baseline
Dual Head punch installed (3-16-09)
Fig. 2
the elastic behavior of the punched hole. The company (www.mom- tools.com) refers to this as a dual-head punch.
The key to its design is the patented annular groove (Fig. 1). Unlike most
single-stroke punch designs, this is not a step punch.
Each punch and die matrix is designed for a spe- cific application and they work together as a sys- tem; you cannot simply purchase a punch. The annu- lar groove is designed to take advantage of the elastic behavior of the stamping mate- rial after the slug breaks free, and it
also acts to facilitate efficient scrap- ring removal.
Again, this punch design should not be confused with a conventional step punch. There have been instances where the company designed the first cutting
edge on the punch larger than the sec- ond cutting-edge diameter, due to the elastic behavior of the hole being punched. This is contrary to a typical step punch design where the first cutting diameter is always smaller than the sec- ond cutting (or shaving) diameter.
The dual-head punch technology is being tested by several Tier 1 automo- tive suppliers and by an OEM automak- er. The results of one test, shown in Fig. 2, show some interesting promise.
Personally, I have no experience with this company or their product—other than being introduced to them recent- ly through another reader of this col- umn—nor is it my desire or intent to endorse companies or products in this forum. However, the engineering prin- ciples underlying this particular punch design makes sense to me and I offer it as a potential solution to your problem and as a technology that others may want to investigate further on their own. MF
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METALFORMING / SEPTEMBER 2010 35
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Number of Cycles