^ IPG Photonics’ Laser Seam Stepper LSS1 / C-Gun (Source: http://www.ipgphotonics.com/Collateral/Documents/English-US/Laser_Seam_Stepper_IPG.pdf)
Somewhere in the last decade, German automotive maker Volkswagen was looking to replace resistance spot welding. They needed a process capable of strongly welding its high-strength, lightweight material without substantial heat-input. Laser welding was a natural choice.
But then, they would also have to replace the clamping mechanism that is an inherent part of resistance spot welding apparatus. You just cannot produce stellar welds without such expensive and sophisticated fixtures.
IPG Photonics solved the problem by including a clamping system in the weld head of the laser weld machine. LSS1’s first prototype passed test in 2010 at Volkswagen. It has not looked back since.
For one, it addresses all the three essentials for an excellent laser weld viz. correct clamping that maintains a constant gap between the base metals, appropriate enclosure, and clean fume-and-spatter-free environs.
What is more, the technology has also opened up the possibility of manual laser welding. Of course, the LSS1 can only weld lap joints at present, not groove or butt joints. Plus, it is not as fast as typical laser welding machines and has miles to go before it becomes a pervasive instrument.
Technical & Operational Details
Maintaining a uniform gap with the required clearance between the to-be-welded materials is the paramount requirement for producing top-class laser welds. Refined fixtures cater to this need but only after you invest valuable resources and priceless time.
LSS1 includes the clamping mechanism in the welding head, similar to a resistance welding gun. On alignment, the head establishes a flexible joint between itself and the workpiece through a servo-controlled-force-system.
Being balance-controlled, the clamp realigns with the 3kN clamping force according to the shape of the workpiece. This maintains the necessary clearance while also preventing workpiece distortion.
|Welding Speed (Max)||80 mm/s|
|Wobble Amplitude||± 1 mm|
|Oscillation Frequency||3 to 30 Hz|
|Focusing Optics||250 mm|
|Press Capacity Servomotor
|0.5 to 3.0 kN|
|Transverse Path (Z Axis)||130 mm|
|Transverse Path Welding Head (Join Length)||40 mm|
|Weight||< 80 kg|
Safety is an overreaching concern particularly when employing laser beams of 1-micron-wavelength for welding. The head-workpiece joint is equivalent to a Class 1 enclosure and nullifies the need for a large, pricey safety enclosure around the work-cell. Call it economical safety.
An integrated control system guides the LSS1’s operations. The servomotor inside the head moves the laser for maximum 40mm length. The welding optic is mounted on this motor. A pivot point guides the laser along a weave with frequencies of:
- 0Hz: gives a zero weave, straight line bead
- 30Hz: provides a strong weave bead that looks like a very thick straight bead
Bead or weld bead is the filler metal deposit created by a single welding pass. A straight pass creates a stringer bead while a zigzag pass generates a weave bead. Weave beads effectively weld wide gaps while stringer beads seal narrow gaps.
A suction head between the workpiece and the weld optic absorbs fumes and spatter. A circular nozzle near the cover-slide module on the bottom can pump shielding gas or compressed air as needed.
Strong weld despite low heat-input is the flagship merit of laser welding. With concentrated heat, lasers weld quickly. This minimizes heat-input that causes distortion i.e. the expansion-contraction of the weld metal and the base metal during the heating-cooling cycle of welding.
Other benefits of LSS1:
- Better Quality vis-à-vis conventional welding processes and conventional laser welding. With greater weave length, the LSS1 provides a 2.5mm weld interface compared to the 0.5mm given by conventional laser welding
Such weaves extend the joint length three times. Superior joint quality provides improved rigidity and upgraded component strength
- Faster Execution: at two times the speed of resistance spot welding. Resistance welding robots take about 2.5-3 seconds for depositing one welding spot. Present standards require a resistance spot weld every 30-50mm length
- Economical: as the clamping mechanism eliminates the need for expensive fixtures and the safety enclosure
- Safety via sensor systems and certified safety functions
- Smaller Flange Size vis-à-vis those for resistance spot welding
- Greater Flexibility in Weld Geometry
- Exceptional Repeatability
Adaptations make LSS 1 capable of delivering welds for those heavy industrial applications that require access from one side. The head applies a vertically downward force of up to 1kN, but the workpiece needs support from the rear. Such applications include:
- Railcar Production
- Agricultural Equipment
- Automotive & Tier-1 Automotive Suppliers
- Steel Furniture
- Welding Galvanized Material
Innovations, big or small, hold the potential of radically altering the way we do things. At first sight, the Laser Seam Stepper LSS1 / C-Gun appears to be one such fantastic piece of equipment.