A laser welding machine is a machine that uses a high-energy pulsed laser or CW lasers to irradiate a workpiece for welding purposes.It can regulate the energy of the pulsed laser by setting different laser frequencies and pulse widths to weld the workpiece accurately.
Working principle of laser welding machine
A laser beam is produced inside of the ruby crystal. The ruby crystal is made of aluminium oxide with chromium dispersed throughout it. Which is forming about 1/2000 of crystal, this less than natural ruby. Silver coated mirrors are fitted internally in both sides of the crystal. The one side of mirror has a tiny hole, a beam comes out through this hole.
A flash tube is placed around the ruby crystal, which is filled with xenon inert gas. The flash is specially designed such as which is made flash rate about thousands flashes per seconds. The electrical energy is converted into light energy, this is worked by flash tube.
The capacitor is provided for storage the electrical energy and supply the high voltage to flash tube for performed appropriately. The electrical energy discharged from capacitor and xenon transforms the high energy into white flash light rate of 1/1000 per second. The chromium atoms of ruby crystals are excited and pumped into high energy. Due to heat generating some of this energy is lost. But some light energy reflected mirror to mirror and again chromium atoms are excited until loss of their extra energy simultaneously to form a narrow beam of coherent light. This comes out through the one end tiny hole of crystal’s mirror. This narrow beam is focused by an optical focusing lens to produce a small intense laser beam on the workpiece.
Laser beams change when interacting with material
Laser energy absorption of a material varies based on a number of factors, such as wavelength, material thickness, crystalline structure, material additives, molecular structure, and more. The process takes the advantages of these material properties and laser to create a bond between two plastic materials—one that transmits the laser energy and one that absorbs it. When a laser beam encounters any material such as plastic, it will either be transmitted, reflected, or absorbed based on the wavelength and the composition of the material it encounters. Most materials exhibit some degree of all three effects, but in varying proportions. A material may be optically clear to light in the visible spectrum and very absorptive to infrared laser, or be opaque to our eyes but transparent to infrared laser.
Why Choose A Laser Welding Machine Over Traditional Forms?
TIG and MIG welding have long been recognized as good choices for welding small components because of their excellent finish. However, such welding requires skill and dexterity, and despite their controllability, suffer from several disadvantages. Laser welding is an excellent substitute that frequently outperforms arc welding processes, and its tightly focused beam limits heating effects. Laser welding is capable of welding tasks beyond the capability of traditional welding methods.
Traditional Welding Methods
TIG and MIG processes use a shielding gas to create an inert atmosphere around the welding head. With TIG, the arc is created by a tungsten electrode, and a hand held filler material used, whereas with MIG welding the electrode is the filler wire. These welders can be adjusted to permit welding of delicate components and the final weld quality is high. Another frequently used method is spot-welding which works by clamping parts between a pair of electrodes and passing an electric current. All arc and spot-welding processes transfer a significant amount of heat to the work piece, affecting the metallurgical structure around the weld.
The heat required for welding is supplied by a tightly focused light beam with a diameter as small as two-thousandths of an inch. Welding is conducted by firing a series of short pulses that melt the metal to create a high-quality weld. Depending upon the particular welding task, filler material may be required as with TIG welding. Because the laser beam is tightly focused, heat input is minimized and parts can be handled almost immediately.
Advantages of Laser Welding:
- Heated Area – The heated area of the weld doesn’t spread to the rest of the material and due to rapid cooling, the material can be handled almost instantly after the job is done.
- Deformation – There are minimal deformation and shrinkage in the material due to the process used for laser welding.
- Weld Strength – As the laser weld is narrow and has an excellent depth-width ratio, the weld strength is truly better than Tungsten Inert Gas (TIG) and Metal Inert Gas (MIG) welding.
- Metals – A whole array of metals such as carbon steel, stainless steel, titanium, high strength steel, titanium, precious metals, and aluminum can be welded.
- One-sided – Spot welding(which requires access to both sides of the material) can be replaced with laser welding, as it needs access to only one side.
- Precision – In comparison to TIG and MIG welding, laser welding offers a much more precise weld. You will find it hard to match a weld as precise we can get from laser i.e. 0.025mm. Moreover, laser welder doesn’t require the skill than conventional welding does and works from computer input, unlike conventional which requires somebody to operate the machine.
- Scrap – Due to high precision, laser welding produces less scrap as there are rarely any errors.
Which Laser To Choose For The Laser Welding Machine?
A laser welding machine can be operated with one of the following two types of lasers – a pulsed laser or a continuous laser. The choice of one over the other depends on the thickness of one over the other. Let’s look at the benefits of both below.
Benefits of Pulsed Laser:
- Sheet metal, gold jewelry chain links, titanium pacemakers, razor blades, are used to weld with a pulsed laser.
- This type of laser prevents the metal from being melted or deformed.
- Suitable for metals that are thin and light.
Benefits of Continuous Laser:
- Compared to the pulsed laser, this is more expensive. It also reduces operating costs.
- Mostly effective on refractory metals.
- Recommended for welding thick parts.
- It can cause problems if used on metal or a part that is too thin. In such cases, the laser can damage, melt, or deform the part.
How To Choose The Laser Beam Source?
In laser welding applications, the three types of laser beam sources most commonly used are – solid-state (nd:YAG) lasers, which uses a solid gain medium; gas (CO2) lasers, which uses gasses such as carbon dioxide as a gain medium; and fiber lasers, which use rare-earth element-enhanced optical fiber as the gain medium. The choice of the laser beam source depends on the type of laser that you have chosen i.e. pulsed or continuous.
1) Solid-state (nd:YAG) lasers – The solid-state (nd:YAG) lasers produce discrete pulses of controllable energy which can be shaped to create the ideal weld. Suitable for producing large spot welds, as well as seam welds and deep spot.
2) Gas (CO2) lasers – As the name suggests, this is a type of gas laser. The electricity is run through a gas-filled tube, producing light in this device. One more interesting feature in this type of laser is the ends of the tube are mirrors, where one of which is fully reflective, and the other which allows some light through. Nitrogen, carbon dioxide, hydrogen, and helium are generally the composition of the gas mixture.
3) Fiber lasers – A low-cost way of achieving high-quality spot welds as the fiber lasers are versatile. They can be used for a variety of applications from welding very small parts together commonly used by manufacturing businesses in the medical, engineering, and electronics industries to welding thicker materials in the aerospace and automotive industries.