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can be programmed for when the tool contacts the part material–‘kissing’ the material instead of slamming into it,” he says. “This reduces the shock load at impact. Thirdly, especially when punching and forming higher-strength steels and special aluminum alloys, metalformers can program a silent- blanking type of profile at the critical point in the stroke where the actual blanking occurs.”
A silent blanking-motion profile, which refers to decreased noise levels as the tooling blanks part material, fur- ther reduces shock and vibration. Besides decreased shock and vibration, lowering punch velocity at key points in the press stroke significantly reduces
heat generation, which also helps improve die life.
“Over the past 15 years, we have worked with many metalformers that use complex progressive dies,” explains Southwell, “Some of them, running the same tools on a repetitive basis, were well aware of tool life and time between sharpening. Through these metalform- ers we have seen tool-life increases of 200, 400 and even 800 percent between sharpening when carrying over dies to properly programmed servo-mechan- ical presses. Some metalformers have been able to justify the purchases of servo presses on tool-life improvement alone.”
Snapthrough Addressed
As with other types of tooling, com- plex progressive dies can be negatively impacted by snapthrough forces. As hinted at above, servo-mechanical presses bring much to the table in com- bating these forces and their detrimen- tal effects.
“When a tool engages part material, snapthrough directly relates to the speed at which the tooling cuts through the materials,” Southwell says. “If, in programming a servo-mechanical press, you can reduce velocity just for that very short impact distance, say from 100 to 20 percent, you typically can reduce the shock load by about the same percentage. So, shock load decreases by 80 to 90 percent.
“This decrease not only lessens the noise of impact,” he continues, “but also reduces vibration as the punch and die come together.”
Interference between the punch and die via vibration causes tools to chip and wear, and can, long-term, harm press components. Thus, eliminating vibration pays dividends.
“In the short term, tool life and part quality improve,” says Southwell. “Longer term, metalformers experience significant improvement related to press wear and maintenance.”
Proper Programming Needed
As Southwell explains, manipulating
stroke length and speed along the stroke length pays big dividends. The key is to properly program a servo- mechanical press to optimize these settings.
“Even though metalformers want to minimize shock and vibration at the point of contact, they don’t want to slow down the entire process,” says Southwell.
Here is where productivity gains are accomplished, and where press and control providers can greatly assist metalformers.
“For example, we work with our customers to apply programming to their particular applications,” South- well says. “Our servo-application engineers work with metalformers to optimize their tooling. Typically, we’ll take a die and determine the needed working stroke, and work through snapthrough challenges based on tool complexity, punching and forming requirements, and the material to be worked.”
From there, engineers program the stroke length to best achieve good part quality and ideal tool life. Then, speed and force intervals are tackled to improve productivity. In the case of many progressive-die applications, according to Southwell, that means shortening the stroke length. The result?
“While the press might only be run- ning, in old-school terms, at 40 strokes/min. in a full revolution, in actual parts produced/min. it now runs at 90 or 100,” he explains. “Though tool- ing seems to be running at a low veloc- ity, the metalformer is obtaining a mas- sive improvement in throughput.”
Thus Southwell has pinpointed where a servo-mechanical press, prop- erly tuned to the tooling and the appli- cation, in a sense becomes the elite athlete, performing seemingly effort- lessly, yet quite effectively.
“Servo presses require a larger initial investment, due to the motors and con- trols,” summarizes Southwell. “But metalformers have realized rapid ROIs due to improved productivity and tool life.” MF
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