Laser welding process

Overview

Laser welding is one of the important aspects of materials engraving processing technology, mainly divided laser welding and continuous laser welding.

Pulsed laser spot and seam welding is used primarily within the thickness of 1 mm thin-walled metallic material, which belongs to the heat conduction welding process, i.e., laser radiation heating of the workpiece surface, and then diffuses through the internal heat transfer based material, by controlling the waveform of the laser pulse, the width , peak power and repetition frequency and other parameters, so that a good connection is formed between the workpieces. In the 3 C product casing, lithium batteries, electronic components, mold welding industry has a large number of applications. The biggest advantage is the pulsed laser welding workpieces overall temperature rise is very small, small heat affected area, the workpiece deformation.

Most of the continuous laser welding high-power, 500 watts or more, usually more than 1 mm plate should use this laser. Its mechanism is based on the deep penetration welding hole effect, the aspect ratio can be achieved 5:1 above, welding speed, thermal deformation. In machinery, automobile, shipbuilding and other industries has been widely applied. There are some low-power continuous laser power between tens to hundreds of watts, they are used most often in plastic welding and laser soldering these industries.

works:
First, the laser power pulsed xenon lamp lit by a laser pulse discharge xenon lamp power supply, a certain frequency, pulse width certain light waves, the waves radiated through the condenser chamber to Nd 3+: YAG laser on the crystal, inspired Nd 3+: YAG laser crystal light, and then after the laser cavity resonance, issue a wavelength of 1064nm pulsed laser, the pulsed laser through the beam expander, after reflection, (or via optical fiber transmission) focus on playing in the desired weld objects; in the PLC or industrial PC under control, mobile CNC table to complete the welding. Frequency, pulse width, wave, table speed, the moving direction of the welding laser pulses required are available microcontroller, PLC, or industrial PC controlled by the frequency of the laser pulse width can be adjusted to different settings to control the pulse laser energy.

Fiber works:
When the pump light through the fiber rare earth ions, will be absorbed by the rare earth ion. Then the absorbed photon energy rare earth atoms excited to a higher electronic lasing level would be to realize the ion inversion, the inverted number of ions in the form of radiation will be transferred from high energy level to the ground state, and the release energy, completed by stimulated emission of radiation. Generated by the fiber laser optical output, and with the support of the table with the completion of the appropriate welding. Fiber lasers into the pulse fiber laser and continuous fiber lasers. Among them, pulsed fiber lasers can be used to adjust the laser pulse energy through a single point of peak power laser frequency, pulse width setting; continuous fiber lasers by setting the average laser power to regulate the output laser power. The working principle of the semiconductor laser: through certain incentives in the energy band of the semiconductor material between the (conduction band and the valence band), or the impurity band of the semiconductor material (acceptor or donor) between the energy levels, to achieve non-equilibrium number of particles in the carrier reverse, when a large number of electrons and holes recombine in the population inversion state, they generate stimulated emission effect. The semiconductor laser generates a laser welding can also be output through the optical fiber.

Characteristics:
Laser welding is a new type of welding, laser welding, mainly for thin-walled materials, precision parts welding can be realized spot welding, butt welding, stitch welding, seal welding, etc., and its features are:

• With a high aspect ratio, weld width is small, small heat-affected zone, small deformation, welding speed.
• Welds smooth, beautiful, no treatment or simple treatment process after welding.
• High weld quality, nonporous, can reduce and optimize the base metal impurities can be refined after tissue welding, weld strength, toughness, at least equivalent to or even more than the base metal.
• Can be precisely controlled, focused small points of light, high-precision positioning can be easily automated. Some welding can be achieved between the dissimilar materials.

Weldable materials and industrial applications:

Laser welding can be applied to a variety of metal alloys of titanium, nickel, tin, zinc, copper, aluminum, chromium, niobium, gold, silver and its alloys, and steel, Kovar alloy welding material between the same species, may also be used in copper – a variety of dissimilar metal weld between copper – nickel, nickel – titanium, copper - titanium, titanium – molybdenum, brass – copper, mild steel.

Widely used in mobile communications, electronic components, eyeglasses and clocks, jewelry, metal products, precision instruments, medical equipment, auto parts, gifts and other industries.

Comparison of laser welding with traditional welding methods

Welding methods	Heat affected zone	Heat distortion	Weld quality	Whether to add solder	Welding environment
Laser welding	Small	Small	Good	No	No special requirements
welding	general	general	general	Yes	Overall warming
TIG	Large	Large	general	Yes	Required electrode
Resistance Welding	Large	Large	general	No	Required electrode
Plasma Arc Welding	general	general	general	Yes	Required electrode
Electron beam welding	Small	Small	Good	No	Vacuum

The style of Laser welding machine
I produced the laser welding machine product types: one type of welding machine and laser optical output matching welding systems. Optical output laser welding system is complete with standard laser system closer to the user needs welding table (workstation or pipeline) constituted improve weld quality and efficiency; fiber laser output into: YA G optical output pulse lasers, pulsed fiber lasers, CW fiber lasers, semiconductor lasers and the like. Which contain fiber output pulse YAG laser WF series and PB series.

The difference between various types of lasers


The difference between the non-fiber output pulse YAG laser and optical output pulse YAG laser



The difference between the current feedback control and laser power feedback control Energy splitting, splitting time with the high-speed spectroscopic (with three-way splitter for example)
High-speed spectroscopic: In addition to the energy splitting, splitting time outside, my company’s laser spectroscopic methods as well as high-speed spectroscopy. Different from traditional shutter, high speed spectral energy at an average frequency of 80Hz to quickly switch the optical path, efficiency is greatly improved. Which, when multi-position welding, the speed advantage is obvious. Not only can greatly save the cost of equipment, it can effectively reduce equipment footprint, the corresponding maintenance costs can also be savings.

Using Laser Technology for Medal and Coin Production in the Mint Industry

Introduction

Medal and coin production is a complicated and time-consuming process and involves many people, from artists and craftsmen through to workers in electroplating and minting. Besides this, multiple machines are used to produce these valuable objects. However, unlike conventional production technology, lasers bring a contemporary approach to production technology and laser engraving solutions, in particular, provide a greater scope for design and contribute significantly toward “leaner” production.

Laser Engraving Machines

Figure 1. GP9000 laser engraving machine. 

FOBA’s GP9000 laser engraving machine (Figure 1) is a light design machine that provides excellent finishing, micro inscriptions, and forgery-proof latent images for security. Precision manufacturing and advanced machines are required to produce perfect medals and coins. To this end, mints employ laser technology in their medal and coin production process because laser-based production processes provide endless design possibilities and potential savings.

Advantages of Laser-based Engraving Process

Laser-based engraving process provides more variety and increased security. Conventional mechanical engraving requires further work processes and hardening times. On the other hand, the laser is capable of engraving directly onto the hardened material. When materials are hardened at the end of the process, the material often gets distorted. However, accuracy can be improved by working directly on the hard material.
Surface finishing offers mints a greater scope for design, resulting in new product innovations. For instance, structures produced through laser engraving systems cannot be achieved with traditional processes. In addition, important security features such as micro inscriptions and micrometer-sized symbols can be produced by lasers cost-effectively and with a high degree of repeat accuracy. Laser-based finishing also saves significant amount of time.

Engraving and Relief Processing Tools and Software

The minting dies and tools used for creating coins and medals are processed manually by engravers. Hence, it is imperative to invest in craftsmanship and technological support. Extensive planning and implementation of a coin or medal project is as time-consuming as it is complex.

Figure 2. A globe for FOBA.

Figure 3. The plaster relief. 

Steinbichler Optotechnik, FOBA’s process partner, develops high-precision optical measuring systems and the related software solutions for various fields of application, including high-precision digitallization of, for example, artistic models or historical coins for the mint industry.Steinbichler’s COMET L3D portable 3D scanner (Figure 4) was utilized to digitalize the FOBA globe relief (Figure 2).

Figure 4. The plaster template is scanned into the system. 

Delcam, another FOBA partner, develops advanced CAD/CAM and 3D measurement software for the manufacturing industry. The ArtCAM Pro 2012 engraving and relief processing software is used by FOBA. Delcam has developed in collaboration with FOBA a tool for this software to transfer the layered 3D models to the laser.

Process Steps involved in Laser-based Medal and Coin Production

Using the FOBA medal as an example, a plaster relief (Figure 3) is first created that serves as a model of the artwork to be digitalized during the next stage. Then, the model of the artwork i.e. plaster relief is scanned using a 3D scanner – for the FOBA medal, a Steinbichler COMET L3D. With it, the three-dimentional point cloud is exported as an STL model.
Prior to engraving, the live image of the die blank is recorded by the IMP camera system and displayed in FOBA EMC. The scanned 3D data (raw stl. file) is opened in the ArtCAM Pro engraving and relief processing software package, where it is edited and processed directly. Then, the text that appears on the medal is positioned here in the form of 2D vectors, and the 2D graphics designed on the PC for the obverse of the medal are transformed into 3D reliefs. The text, 3D relief data, and enhanced stl. file are then compiled.
Following this, the 3D models earlier compiled into layers with very small layer thickness are split by the software. Through a USB stick, this data can be imported into the FOBA EMC, which serves as the core control software for all engraving applications with FOBA engraving lasers.

Figure 5. Obverse and reverse male molds of the FOBA medal.

The GP9000 laser engraving machine directly works on the hard material and engraves the defined relief of the reverse and obverse of the medal (Figure 5) into two brass blanks using a high-precision laser beam. The male molds of the FOBA medal are then subjected to electrochemical machining. The result of this machining includes the following:

• Working dies are subjected to sand blasting, glass bead treatment and polishes.

Following this, there is the laser processing step of working dies (frosting, latent image, and micro inscription), which is then followed by electroplating of minting dies and the final step of minting.
The complete laser deep engraving of a die is a time-consuming process when compared to CNC milling. However, the benefit of laser technology is that it does not have any hardness limitation when processing steel and the work is performed directly on the hardened material.

Conclusion

In coin and medal production, laser technology can be utilized in many different ways, particularly where mechanical processes reach their limits. Laser engraving machines produce finer and more detailed textures and structures. The material’s hardness is also irrelevant since processing takes place directly in the hardened material.

About FOBA Laser Marking & Engraving Solutions

FOBA have focused on laser marking and engraving for decades and are experts by experience. Such focus on technology, our consistent focus on challenging applications and complex jobs and one of the broadest product ranges in the market allow us to offer our customers optimal and custom-tailored solutions for their identification applications.
From OEM laser markers to laser marking workstations to high-precision laser engraving machines; from standard- to customer-specific solutions: Depending on the requirement, we integrate various laser technologies, add value-adding accessories and options such as vision systems and provide system and machine solutions that are perfectly designed for the marking or engraving job at hand. To Shanghai, Bremen or Ottawa.

This information has been sourced, reviewed and adapted from materials provided by FOBA Laser Marking & Engraving Solutions.