I. Preface
As an essential sector of the machinery manufacturing industry, engineering machinery has multiple categories, complex functions and high structural strength.
Although it rarely served as a testing ground for various new production technologies, the innovative spirit of scientific and technological personnel and their courage to overcome difficulties ensured the eventual diffusion of new technologies in the field of engineering machinery production. This includes welding robots, automation, smart logistics and others.
Naturally, the industry also favors laser processing technology, which is a green, environmentally friendly, efficient and contactless object processing technology.
II. T the features of laser processing
Laser processing originated in Germany in the 1960s and primarily uses high-energy particles produced by lasers to melt and vaporize the surface of the part. This principle is used for several derivatives processing technologies.
Laser beams offer high stability and anti-interference and impose fewer restrictions on the workpiece (such as processing way, size and environment), enabling precise and high-quality processing of most metallic and non-metallic materials.
Laser processing technology is known for its high precision and specialization. Its characteristics and advantages can be summarized as “high, fast, good, economical and versatile” as follows:
(1) High
Laser processing offers high precision, processing efficiency, material utilization and economic efficiency.
For example, a laser cutting machine priced at $50,000 can help a company recover the cost of the equipment and generate profits within a year and a half of normal processing.
(2) Fast
Laser processing features a fast processing speed because the laser energy medium is the light source. It can reach speeds of up to 100m/min.
Currently, the most advanced 3G laser cutting machines are 1.5 times faster than conventional processing equipment.
(3) Good
Laser processing is highly resistant to interference and is not easily affected by environmental factors. This results in parts of exceptional quality and precision, which can be at the same level (micron level) as those produced by finish machining of common machine tools.
(4) Save
Laser processing is known for its material efficiency as it consumes less material than other processing technologies. Incomplete statistics suggest that laser processing can save between 10% to 30% of materials.
Furthermore, laser processing is a non-contact process, which requires fewer consumables for the equipment. This significantly reduces production costs.
(5) Wide
Laser processing is a versatile technology that can be applied to a wide range of materials, not limited to metallic materials but also non-metallic materials.
Additionally, laser processing can handle a wide range of shapes, including straight lines, curves and molded patterns, making it a truly barrier-free technology.
III. The application of laser processing technology in engineering machinery manufacturing
In recent years, due to advancements in laser processing technology and equipment, it has become more prevalent in various processes involved in manufacturing construction machinery products.
The following is an overview of current technology used for construction machinery applications:
3.1 Laser processing technology in the field of sheet metal cutting applications
Laser cutting is a cutting method that uses a laser beam produced from a laser oscillator. The beam is focused through a focal mirror to generate high-density energy, which is then directed into the material, causing it to melt and evaporate.
Compared to other thermal cutting methods such as flame and plasma, laser cutting can achieve higher precision with smaller slits due to its large energy output per unit area.
The company's blanking center, which serves the needs of construction machine manufacturers such as Carter, Komatsu and John Deere as well as local support companies, has more than 100 pieces of equipment in six categories: fine plasma cutting, fiber laser, flat cutting, bevel cutting, pipe intersection line cutting, integrated drilling and cutting machines and steel section cutting.
This equipment includes three two-dimensional laser cutting machines (see Figure 1) and two three-dimensional laser cutting machines (see Figure 2). Laser suppression is used on a wide variety of construction machinery parts and components, including hoods, fuel tanks, cabs, and more. The cut materials range from general Q235A plates and profiles to 1000MPa high strength, with a thickness of 1 to 25mm. The center has an annual cutting capacity of 20,000 tons.
Figure 1 Two-dimensional laser cutting machine 
Figure 2 3D Laser Cutting Machine
Currently, there are two main types of laser cutting machines used in the engineering machinery sheet metal processing industry: CO 2 laser cutting machines and fiber laser cutting machines.
The CO2 laser cutting machine is an earlier product and its technology is not as advanced as the fiber laser. The wavelength of the CO2 laser is about 1/10 of that of the fiber laser, and propagation is generally carried out in an isolated optical path to protect it from external air.
On the other hand, the fiber laser propagates in the fiber, providing better beam passability and higher energy, resulting in less thermal influence and narrower cutting lines. This is beneficial to improve cutting efficiency, material utilization and reduce thermal deformation during plate cutting.
In addition to conventional laser cutting and blanking, laser cutting technology offers advantages in cutting circular holes, reserved process gaps and producing process templates. It can be applied to “cut rather than drill” holes in process equipment, saving time during the drilling process, improving production efficiency and reducing the cost of drilling jigs.
3.2 Application of laser processing technology in welding
Most traditional welding techniques used on construction machinery involve gas shielded welding, submerged arc welding, or argon arc welding. However, these methods often result in quality defects such as excessive splashing and distortion. Furthermore, the light and dust from the welding arc can pose a risk to the physical and mental health of the operator.
With technological advances, industrial product manufacturers have worked to improve welding quality and efficiency and reduce manual labor in construction machinery welding processes. They gradually introduced concepts from the automotive industry such as robotic white body welding, assembly lines and flexible manufacturing.
In the past, laser welding technology was not commonly used in engineering machinery products due to insufficient power and limited capabilities for medium-thick or ultra-thick plates. However, in recent years, renowned universities such as Shanghai Jiao Tong University and Harbin Institute of Technology have conducted extensive research and experiments on medium-thickness plate laser welding technology. This has led to the development of high-power laser deep fusion welding, compound arc welding, ultra-narrow gap multilayer fillet welding, and vacuum negative pressure laser welding, among other welding methods.
Hybrid laser arc welding technology has been successfully applied to construction machinery crane boom. It combines two heat sources with completely different energy transmission mechanisms and physical characteristics to act in a unified welding position. This results in greater weld depth, greater gap bridging capacity and greater welding efficiency, creating a 1+1>2 effect.
For example, the material of the reach arm of a truck crane is high-strength steel with a yield strength of 960 MPa, which is laser double-wire MAG composite welding (see Figure 3). Compared with traditional welding methods, this approach has strong welding adaptability and can be used for high reflection welding, difficult welding and welding of dissimilar materials. It also improves the stability of the welding process and weld formation, while eliminating welding defects to improve the quality of the weld seam, achieving a 100% inspection pass rate. Furthermore, efficiency increases by 300%.
Hybrid welding is also more efficient than single heat source welding as it can effectively increase penetration depth by 50%, increase welding speed and ensure lower heat input. Furthermore, it has higher filling efficiency and saves more than 30% of unit yarn consumption.
Fig. 3 Example of MAG welding application with laser compound
3.3 Applications of laser processing technology in remanufacturing
In recent years, the construction machinery remanufacturing business has developed rapidly. On the one hand, the country strongly defends green production, which includes saving energy and reducing consumption.
On the other hand, the performance of remanufactured products is essentially comparable to that of new products, but they cost about two-thirds the price of new products. Users are gradually recognizing this, and companies are also willing to do so because only 40% to 60% of production costs are involved.
Parts remanufacturing mainly involves replacing worn parts, seals and repairing wear in mechanisms. The most important technology used in this process is high-efficiency laser welding, also known as laser cladding.
The main principle is to use a high-power, high-density laser beam to form a microfusion layer on the surface of the substrate and add a specific composition of direct fusion alloy powder simultaneously or preset, in order to achieve the purpose of uniformly repairing worn parts.
This process also belongs to a type of material augmentation manufacturing technology, providing high-quality and viable manufacturing solutions to realize differentiated product customization.
Laser cladding has high flexibility, optional surface area, optional materials and even optional performance. For example, when the track spring cylinder of a high-power excavator wears out during use, remanufacturing can adopt laser cladding additive processing for the worn area (see Figure 4).
Tested from multiple dimensions of wear resistance, the surface hardness is qualified, the layer hardness gradient in the coating layer is reasonable, and the metallographic structure is good. This can increase the service life of the high-power tractor spring cylinder by 300%.
Laser cladding is now not only used for remanufacturing, but also replaces the original chrome plating and pre-induction heat treatment process in new products. This greatly increases the competitiveness of the product in the industry.
Fig. 4 Laser enlargement of the spring cylinder for high-power tractors
3.4 Application of laser processing technology in the field of quality management
The ISO 9000 quality management system requires process monitoring of parts and components, and their quality must be traceable. To effectively track the quality and usage of parts and components, construction machine manufacturers need permanent identification of self-made parts and accessories.
This identification includes basic information such as product name, material number, drawing number, manufacturer, production date and two-dimensional code.
Traditional marking technology uses the continuous mechanical movement of the cylinder to impact the object, leaving a trail of movement on the surface of the sign. However, this method has disadvantages such as large noise, blurred writing and signal deformation.
Laser marking technology is a non-contact processing method that uses the beam emitted by the laser to instantly melt the material on the surface of the workpiece. The laser path on the surface of the material is controlled to form a graphic marking method, as shown in Figure 5.
Compared to traditional methods, it has the following advantages:
- It is faster, with speed more than double that of traditional methods.
- It produces high-quality fonts, clear handwriting, and can print complex patterns, symbols, and letters that are incomparable to traditional marking.
- It is environmentally friendly and pollution-free as it is a contactless processing method. It can be combined with a CNC software system to achieve automatic marking.
a) Pneumatic marking
b) Laser marking
Fig.5 Example of comparison of signaling coding applications
3.5 Conclusion
As demonstrated by the above examples, laser processing technology has been continuously used in various process steps in the engineering machinery manufacturing industry. Laser cleaning technology is gaining attention particularly in the aerospace, automotive, construction machinery and other fields.
This process is capable of removing paint, cleaning molds and eliminating oxidation layers and coatings before welding. It operates at a faster speed and produces less waste, but is used less in today's construction machinery industry.
Most construction machinery companies have incorporated the above-mentioned laser processing technology into their own corporate process standards to improve the quality and efficiency of their products.
As laser processing technology becomes more localized, small and medium-sized businesses are also considering purchasing laser equipment to reduce labor costs and improve product quality.
However, compared with mature standardized applications abroad, domestic processors still have a long way to go.
4. Development trend of laser processing technology
Laser processing technology is a complex system that combines multiple fields such as mechanical, electrical, numerical control, optical and hydraulic.
The technical requirements for companies to enter this field are relatively high, which is why developed countries such as the United Kingdom, Germany and the United States have led the development direction of the laser processing industry.
Although China entered this field relatively late, with the continuous implementation of the national strategy “Made in China 2025”, Chinese laser equipment manufacturers and scientific research institutions have been working hard, and emerging stars such as Han's Laser have narrowed the gap in technology with foreign laser equipment.
Furthermore, the development of laser processing technology is a time-consuming and challenging process that requires the efforts of all aspects of society.
I believe that the future of laser processing technology will focus on the following areas of development.
(1) Laser miniaturization
As a fundamental component of laser processing technology, the size of the laser determines the size of the entire machine.
In the early stages of development, the size of lasers was relatively large and required a significant amount of space due to the limitations of microelectronics and optical technology.
However, with continuous progress and the development of new laser technologies such as optical fiber technology and UV technology, smaller lasers with high conversion efficiency, good working stability and good beam quality have been developed. This advancement provides a solid foundation for the miniaturization of laser equipment.
(2) M multifunctional processing
To meet market demands, laser equipment manufacturers are no longer just focusing on single laser processing functions. Instead, they are developing integrated equipment that can perform multiple functions, such as cutting, welding, heat treatment and spraying. This multifunctional equipment maximizes value for customers.
(3) Equipment Intelligence
With the emergence of Internet technology, equipment intelligence has become another important trend in laser processing technology.
In a smart factory, various production plans and material processing data will be uploaded to the enterprise cloud. Engineers will be able to remotely control equipment operating status from an office using a remote terminal. This approach allows for the digitalization, automation and computerization of the product manufacturing process.
V. conclusion
With the implementation of the “Made in China 2025” plan, laser processing technology has become a crucial tool for promoting the transformation and upgrading of the construction machinery industry due to its incomparable advantages.
Following the widespread adoption of information technologies such as Internet+ and 5G, laser processing and production are also moving towards smart production.
Given the government's encouragement of enterprises to pursue technological innovation, domestic laser manufacturers will continue to increase investment in R&D to provide laser equipment with higher cost performance to the market.
This momentum will fuel innovation of emerging fields and traditional manufacturing processes, while providing technical support for the broader application of laser processing technology in the construction machinery manufacturing industry in the future.
