Page 54 - MetalForming Magazine June/July 2022 80th Anniversary Issue

Fabrication: Resistance Welding
Lobe Curve
The lobe curve is developed by varying force, current and time to find the optimum weldability window or “lobe.” All other conditions remain constant.
Good Welds
Expulsion
Cold Welds
Current
The Variables
RW success starts with understand- ing and controlling its three key process variables—weld force, welding current and weld time (current-flow duration). Several combinations of these variables usually will result in acceptable welds, but it’s best to experiment and destruc- tively test to establish optimized weld- ing-machine settings, called a weld lobe when displayed graphically (see the accompanying figure).
At a given weld force, the best results usually come from selecting a relatively high weld-current setting in conjunc- tion with a short weld time. Anything that changes or affects these variable settings can spell trouble.
Force
Since RW joints are forged during the process, take care to control the amount of force applied. Insufficient force results in expulsion (sparks), while excessive force reduces the interface resistance and can result in a cold weld.
AMADA’s Innovative REGIUS 3015 AJ Series
Equipped with the world’s fastest lin- ear-drive technology and autonomous features, the 6-, 9-, and 12-kW REGIUS series of fiber laser cutting systems reduce the time to process complex nests by 15 percent compared to previ- ous systems.
• Laser Integration System—Monitors and adjusts machine and process parameters with minimal operator input.
• i-Nozzle Checker—Nozzles are regu-
larly inspected for their position, centering, shape and diameter. If damage is detected, the nozzle is replaced automatically.
• i-Process Monitor—Beam and cutting conditions are analyzed to ensure optimal process parameters.
• i-Optics Sensor—Helps to reduce processing defects by automatically detecting debris on the protection glass.
• i-Camera Assist System—A camera inside the safety enclosure works with the AMNC 3i control to efficiently process remnant materials. Parts can be easily moved,
to verify the process, and ensure that the lubricator has not run out of oil.
Another potential source of insuf- ficient force delivery: improper fitup of the workpiece components, resulting in mechanical springback that the welding machine must overcome. This robs the process of its proper force and results in inconsistent welds.
AMADA AMERICA, INC.
Most RW machines employ a pneu- matic force-delivery system; however, electric servos recently have become popular on robotic spot-welding guns and other automated systems. In either case, ensure proper operation of the air cylinder or servo, with no binding of the ram or rocker-arm mechanism. Also, use a calibrated weld-force gauge
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rotated, and placed to achieve on-screen nesting.
• Automatic Collision Recovery—The laser head tilts if a
collision with a tip-up occurs. After a collision, the noz- zle is automatically replaced and cutting immediately resumes at the next NC coordinate.
Amada America, Inc.
7025 Firestone Blvd. Buena Park, CA 90621 877/AMADA-US www.amada.com/america
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