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Laser Spot Welding - Laser Keyhole Welding

Laser Keyhole welding beats conventional spot welding machines on all fronts

Most manufacturers are looking for ways to save money and improve efficiency without negatively impacting quality. Manufacturing operations that are using resistance spot welding can reap significant productivity and quality benefits in some applications by converting to laser keyhole spot welding.

Implementing fiber laser keyhole spot welding can result in a welding process that is three to four times faster compared to resistance spot welding, while also increasing weld quality and repeatability.

Laser keyhole spot welding offers numerous benefits in the right applications, including precise control of penetration depth, a very small beam size for a small heat-affected zone, great consistency, and an extremely fast process.
However, laser keyhole spot welding may not be the right fit for every job. 

Advances in manufacturing technology and the trends for more precise part geometry have opened the door for new metal-joining applications where traditional TIG and resistance welding methods no longer meet precision, quality, or productivity requirements. Pulsed laser spot welding technology is now being used to replace these processes, often with increased productivity and lower overall cost.

Moreover, the demand for greater precision in high-performance assemblies has favored the use of these lasers as a more cost-effective alternative to the resistance welding that has been used for decades. Fiber laser spot welding eliminates problems associated with resistance welding, including electrode sticking, and cleaning or replacement. Also, since laser welding is a non-contact process, there is no metal deformation of the component parts.

Spot welding is the simplest form of laser welding. There are two types of spot-welding modes: conduction and penetration. The conduction welding mode is employed for micro-joining purposes. Penetration welding permits aspect ratios (ratio of depth to width) much higher than unity.

Laser spot welding

Laser spot welding is a non-contact process which uses a laser to create a single weld spot to weld metals together. Lasers are capable of delivering a pulse of light with accurate, repeatable energy and duration. When the pulse is focused into one place – a small spot – (adjustable anywhere from approximately 0.1 to 3.0 mm in diameter) on the part, the energy density becomes quite large. The light is absorbed by the material causing a “keyhole effect” as the focused beam drills into, vaporizes, and melts some of the metal. As the pulse ends, the liquefied metal around the keyhole flows back in, solidifying and creating a small spot weld. This entire process just a few milliseconds.

Lasers can fire many pulses per second, and, by moving either the work piece or optics, allow either separate “spot” welds or a series of overlapping spot welds to create a laser seam weld that can be structurally sound and/or hermetic.

In some sheet metal applications that require resistance spot welding, an automated laser keyhole welding process can save time and improve weld quality. The process is well-suited for welding some dissimilar metals, which can be difficult to weld properly with resistance spot welding because of differences in the physical, chemical, and mechanical properties of the base metals.

Laser keyhole welding uses a powerful laser beam to weld two workpieces together. A high-energy-density laser hits a small pinpointed spot on the material. When light hits the top surface, it melts and vaporizes the metal. The pressure of the metal vapor pushes the liquid metal downward and aside, generating a keyhole. As the laser beam is moved across the surface, the keyhole follows the beam and creates a weld that is typically deep and narrow

In suitable applications, laser keyhole welding offers:

  • Precise control of penetration depth, which eliminates any deformation or indentation on the back side of the bottom part. This reduces the time and money spent on postweld grinding or touchups.
  • A very small beam size — less than 1 mm — that results in a small heat-affected zone. This offers benefits when welding thin materials or metals in which controlling heat input is important.
  • An extremely fast process that is typically three to four times faster than manual resistance spot welding.
  • Consistency and predictability, which result in high-quality finished welds and reduced time and money spent on rework.

Spot and Seam Welding With Lasers

As the names suggest, spot and seam welding refer to welding functions applied to a single point or along a line. By setting a laser spot welder to a high welding speed and an extremely narrow weld geometry, the welder can produce extremely fine spot welding. Alternately, you can adjust the unit to weld on the continuous wave mode, welding with high power. The ideal welding speed for spot or seam welding projects varies according to the particular laser model, the laser power setting, and the material type.

Laser Spot Welding Benefits:

Our WOBBLE-3 handheld laser welders

can join a wide range of steels, nickel alloys, titanium, aluminium and copper.

Weld sizes:
Width: 10 nm - 3000 nm
Depth: 10 nm - 5 mm
Welding speeds:
Range from 0 - 5 meter per second

Advantages of laser spot welding with our Wobble-3

The advantages of the laser technique, compared with arc or resistance welding processes are summarised as follows:

 

Low heat inputs to the materials, minimizing distortion
High process speed; Easily automated process
No weaving required
The only consumable is shielding gas, apart from normal laser requirements
It forms a narrow deep weld, small heat-affected zone
It can be applied in confined areas
Access to only one side of the material is required.
Easy to integrate into production lines 
Small heat affected zone
Contactless welding 
Very fast welding
Low costs per weld for high volume spot-weld application

Comparison of Various spot welding processes

Comparison of laser spot welding with other types of spot welding on the basis of certain welding characteristics summarised in following table

Characteristics Laser Electron Beam Resistance Spot Gas Tungsten Arc
Heat Generation Low Moderate Moderate Very High
Weld Quality Excellent Excellent Good Excellent
Weld Speed Moderate High Low Low
Initial Cost Moderate High Low Low
Operating/Maintenance Cost Low Moderate Low Low
Tooling Cost Low High High Moderate
Controllability Very Good Good Low Fair
Range of Dissimilar Metals Very wide Wide Narrow Narrow

Considerations for Converting to fiber laser spot welding

Converting from resistance spot welding to laser keyhole welding requires considering several key factors to determine if it’s the right choice for the operation and application.
  • Cost: Because laser welding is an automated process, it requires an investment in a robotic welding system. For smaller operations that don’t produce a lot of highly repeatable parts, this type of investment may not be feasible or deliver the necessary return on investment (ROI) to justify the purchase.
  • Tolerance window for material: Proper tooling and fixturing are critical for success in laser welding. The two workpieces to be welded must be pressed together without a gap to create a high-quality laser weld. This makes the right joint and material presentation important, so the operation must be able to support proper setup and part fit-up.
  • Repetition:Laser keyhole welding is best-suited to a repetitive process in which many parts are produced, even if this means a high mix of parts with lower volumes of each part. Because of the necessary investment in system setup, applications with high repetition or high part volume typically offer the best ROI in laser welding.

Considering these factors can help you determine if laser keyhole welding is right for your operation.

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WOBBLE-3 & Wobble-3+: Affordable high Quality Handheld Fiber Laser Welding Machines