Page 25 - MetalForming September 2009

Increased Productivity
Before: 12 parts/min After: 18 parts/min 50% more
Before: 25 parts/min After: 40 parts/min 60% more
Does it make you wonder how much faster your parts could run?
Are you running parts on presses in the range of 300 tons and up?
Schuler’s unique ServoDirect Technology could take your output performance to a whole new level as well. Our calculation program can predict your potential with high accuracy.
Curious? Make an appointment with us at Fabtech, booth#16054, and we’ll be happy to assist you in obtaining a free assessment of any part your company would like to investigate.
To schedule a Fabtech appointment, e-mail us at info@schulerinc.com.
Call us: 734-207-7200
Ask for ServoDrive Sales
Read more: www.schulerinc.com/SDT
Schuler.
Get more. Do more.
today feature a keystoned crosssection produced from pretempered/pretrapped wire or from pretrapped annealed wire, to maximize available material. These springs optimize energy-storage capac- ity, as more material can be allocated into the available space in the die.
Warding off Corrosion
General corrosion, galvanic corro- sion, stress corrosion and corrosion fatigue threaten to reduce spring life and load-carrying capacity. To ward off corrosion and optimize spring life, man- ufacturers offer powder-coated or plat- ed springs whose coatings typically meet or exceed 100-hr. salt-spray testing. These coated springs suffice in most applications.
In more challenging environments, to combat corrosion metalformers can opt for springs with sacrificial coatings —primarily water-based coatings that contain metal oxides and aluminum flakes. Zinc and aluminum platelets align in multiple layers, providing sev- eral advantages including barrier pro- tection, passivation, positive galvanic action and self-repairing (sacrificial) qualities. These coatings, with the addi- tion of advanced sealers, allow die springs to sustain as many as 1000 hr. of salt-spray resistance. The result is a more corrosion-resistant die spring, the reduced likelihood of a spring failure due to surface defects, and a lower coef- ficient of friction.
Standards for Design and Quality
Basic die-design parameters that dra- matically affect spring performance and life include clearance between the spring, pocket and rod. The recommended clearances are based on how the diam- eter of the spring increases during com- pression, and are calculated using a for- mula based on initial spring pitch.
Die designers often find creative ways to optimize the use of space in the die. For example, they can stack springs or nest them—both practices often can reduce cost compared to either increas- ing the size of the die or moving to
nitrogen gas springs. To make it easier for designers to specify and select a die spring for a given application, spring manufacturers have adopted standard designs—originally to the NAAMS (North American Automotive Metric Standards) global standard that emanated in the mid-1990s from the automotive metal- forming industry in an attempt to reduce the cost of stamping-die components, and then to European (ISO) and Asian (JIS) standards. The NAAMS line (defined by the Raymond spring standards and still incorporating the original Ray- mond colors of blue, red, gold and green) continues to lead the way in the United States, followed by ISO and JIS.
All of these standards attempt to increase spring quality while making them worldwide commodities. Quality initiatives such as TS 16949, ISO 9000 and ISO 14000 demand that spring manufacturers continue to implement more reliable and capable in-process SPC controls and advanced CNC coil- ing equipment, to supply consistent- quality-level springs to metalformers, with zero defects.
The Case for Gas Springs
Growing demand from metalformers to develop complex, large tools to form increasingly complex parts requires springs capable of delivering consistent and repeatable forces. This trend has helped lead a transition in some cases to the use of nitrogen gas springs. As the ability to control spring force becomes more critical in these complex applica- tions—typically to prevent wrinkles and tears—tool and die designers find that gas springs provide more consistent loading than do coil springs, but at increased cost. Die designers, therefore, should follow these guidelines when specifying die springs:
• Select the appropriate die springs early in the design process;
• Ensure that the springs are suffi- ciently preloaded;
• Protect the springs from adverse external elements;
• Provide proper spring guidance; and •Maintainequipmentregularly. MF
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