Modern cutting technology and its application in the manufacturing of construction machinery

Modern cutting technology and its application in the manufacturing of construction machinery

In the modern industrial manufacturing field, cutting is one of the fundamental processes with a large application volume and wide application range. Especially in the construction machinery manufacturing industry, the workload of cutting accounts for a large proportion. The efficiency and quality of cutting will directly affect the efficiency and quality of production.

Based on the current status of modern cutting technology and in combination with the specific application of cutting technology in heavy-duty factories in production, a brief introduction to the key points of the selection and application of cutting technology in construction machinery is provided below.

I. The current situation, application forms and technical economy of cutting technology

In recent years, breakthroughs have been made in cutting technology both at home and abroad. It has evolved from the single oxygen-acetylene flame gas cutting to modern cutting technologies that include multiple energy sources and various process methods such as new industrial gas flame cutting, plasma arc cutting, laser cutting, and water jet cutting. At the same time, modern control technology has been combined with cutting technology. Research and develop a new generation of fully automatic cutting equipment.

A. Current Situation

Oxygen-acetylene/new type of gas flame cutting

Since the Frenchman LeChatelier invented the oxygen-acetylene flame in 1895 and Fouch and Picard produced the first oxygen-acetylene cutting torch in 1900, oxygen-acetylene flame cutting, as the oldest thermal cutting technology, remains a processing method in mechanical manufacturing to this day. As the raw material for acetylene production is calcium carbide, a large amount of calcium carbide slag (1 ton of calcium carbide generates 3.3 tons of calcium carbide slag) and toxic and harmful gases such as HS and S0 are discharged during the production process, seriously polluting the environment. At the same time, a large amount of important chemical raw material acetone is consumed in the production of dissolved acetylene gas, increasing the production cost. Therefore, over the past 20 years, relevant research institutions and enterprises at home and abroad have successively invested a large amount of funds to develop and research new types of gas that are low-cost, safe and reduce environmental pollution. Currently, China has independently developed and introduced a variety of new industrial gases to replace acetylene in industrial flame processing. At the same time, cutting torches that are compatible with the new industrial gas have also been successively put into operation, with a complete range of cutting torch types. The cutting thickness of the manual torch can reach 350mm, while that of the machine torch can reach 1800mm.

2. Plasma arc cutting

Plasma arc cutting is a processing method that developed in the mid-1980s. At that time, it was mainly used to solve the cutting of stainless steel and non-ferrous metals. Various processes such as argon, hydrogen, compressed air, nitrogen, and oxygen were successively developed, including general plasma arc cutting and water recompression plasma cutting, to meet different needs.

The output current of a common plasma power supply is 20 to 200A, and the cutting thickness can reach less than 30mm. The output current of the fine plasma power supply can reach up to 100A, and the cutting thickness can be less than 12mm. Among them, the width of the fine plasma cutting seam is 0.65 to 0.75mm. When combined with a CNC cutting machine, it can achieve a cutting accuracy of ± 0.2mm. The output current of the water recompression plasma power supply can reach up to 1000A, and the cutting thickness can be less than 130mm.

At present, the cutting torches of plasma arc cutting machines are developing towards the direction of cutting seam accuracy approaching that of lasers. Low-power cutting power supplies are developing towards inversion to enhance power supply efficiency and the shrinkage of the arc. High-power cutting power supplies are developing towards thyristors and adopting certain compensation measures to enhance efficiency, thereby increasing the cutting speed and improving the cutting quality. In recent years, with the development of plasma arc technology, the cutting of carbon steel and low alloy steel under 20mm has shown a growing trend in the construction machinery manufacturing industry due to its fast cutting speed and good comprehensive benefits.

3. Laser cutting

The industrial application of laser cutting began in the early 1970s. Due to its advantages such as good cutting size quality, high speed, high precision and high efficiency, it has been widely applied in various industries. With the improvement of the power level, stability and reliability of laser devices and the advancement of processing technology, their application fields have gradually expanded to the cutting of various metal and non-metal plates. According to the statistics of 2002, in the global application scope of laser industry, laser cutting accounted for the largest proportion, approximately 24%.

4. Water jet cutting

Water jet, as a precision processing method for industrial products, is characterized by no or very little heat release, no thermal deformation, and no gas or steam emission. Research on this cutting technology began in the 1960s. After more than 20 years of research and development abroad, the first high-pressure water jet cutting equipment was manufactured, enabling it to cut various metals, ceramics and other materials. In the 1990s, China developed and produced domestic high-pressure abrasive water jet cutting equipment and put it into production. At present, most water jet cutting equipment is mainly applied to the cutting of non-metallic plates.

B. Application Form

No matter which cutting technology is used, there are different application forms. Flame, plasma and laser all have small cutting machinery products and CNC coordinate cutting machinery products.

Among them, there are the most small-scale cutting machines for flame cutting technology, ranging from general semi-automatic gas cutting machines, profiling gas cutting machines, photoelectric tracking gas cutting machines to specialized steel section gas cutting machines and saddle-shaped gas cutting machines, with about 20 types. The prices are reasonable, and large, medium and small enterprises are all equipped with them, which can fully meet the cutting production needs of cutting personnel under various conditions. In addition, improvements have been made on the basis of the small cutting machine to meet the process requirements such as U, V, Y, K bevel cutting, spherical bevel cutting and intersection line cutting.

The coordinate CNC cutting machine is one of the fastest-growing modern cutting equipment in China's cutting industry. With its excellent human-machine dialogue operation interface and powerful auxiliary support functions, as well as the support of software systems such as automatic programming and nesting, the coordinate CNC cutting machine has played an important role in production and has become the first choice for cutting processing in China's manufacturing enterprises.

C. Technical and economic comparison

At present, thermal cutting is widely used in the construction machinery industry. Flame, plasma and laser cutting technologies all belong to thermal cutting. The technical and economic comparison of the three cutting technologies is shown in the following table.

Technical and economic comparison table

Flame cutting machines have large cutting deformation, relatively low cutting speed, and require preheating before cutting, which takes a long time. However, they can use multiple cutting torches for simultaneous cutting, and the service life of consumable parts is long. Although plasma cutting can cut all metal plates and many non-metallic materials, with a maximum cutting speed of up to 10m/min, which is ten times that of flame cutting, its cut width is relatively large. Except for thin plates, the cutting surface is prone to "edge collapse", but it can economically cut medium and thick plates. Although laser cutting machines are expensive, they can achieve high-speed and high-precision cutting of thin and medium-thick plates, and at the same time, they can operate unmanned.

Ii. Manufacturing Process Requirements for Construction Machinery

In the production and manufacturing process of construction machinery, cutting and welding workpieces have their inherent characteristics:

There are more welded parts made of low-carbon steel and low alloy high strength steel for engineering purposes, followed by decorative stainless steel, and very few non-ferrous metals and non-metals.

2. The annual consumption of steel is large. Taking heavy duty plants as an example, the maximum throughput is nearly 10,000 tons per month

3. Carbon steel welded parts mostly use medium and thick plates. For instance, plates within 20mm account for over 80% of the total steel consumption in heavy industry plants.

4. The workpieces manufactured by construction machinery have particularities:

A. There are many types of workpieces, and the types of materials are relatively concentrated.

B. Long-term conditions carry a certain weight;

C. The workpiece has a large bevel volume, and the bevel forms U, V, Y, and K are diverse and irregular.

D. Some workpieces have complex shapes and high precision requirements.

Iii. The Application of Cutting Technology in Construction Machinery

In response to the technological requirements of the cutting objects in construction machinery and in combination with the characteristics of various cutting technologies, the construction machinery manufacturing industry has a purposeful approach when selecting various cutting technologies and cutting equipment:

Water jet cutting, due to its large initial investment, complex construction and being a precision processing method, is currently not suitable for metal cutting in construction machinery. However, the other three cutting techniques can all be applied in the construction machinery manufacturing industry.

2) The cutting equipment in the construction machinery manufacturing industry mainly adopts mechanized and automated gantry-type CNC cutting equipment, supplemented by small-scale cutting equipment.

To enhance cutting efficiency, material utilization rate and meet the annual steel cutting demands, the construction machinery manufacturing industry should mainly adopt mechanized and automated coordinate CNC equipment as the blanking method. This not only saves manpower but also significantly reduces secondary processing. In recent years, due to continuous development, heavy industry factories have accelerated their technological transformation, and their processing methods have also undergone a leapfrog development, evolving from the previously backward secondary processing and multi-head flame cutting to CNC cutting technology. At present, the factory has as many as 13 sets of CNC coordinate equipment, and is supplemented by a small number of small gas cutting and shearing equipment to process material heads and edges, improve material utilization rate and solve the blanking of small parts.

3) Plasma and laser cutting equipment should account for a certain proportion in the construction machinery manufacturing industry.

Due to the extensive application of medium and thick plates in construction machinery and the fact that long strip-shaped workpieces are prone to deformation, in order to enhance efficiency and quality and improve the overall production benefits, coupled with the complex shapes and high precision requirements of some workpieces, the construction machinery manufacturing industry will need to increase the proportion of plasma cutting and laser cutting equipment in the selection of cutting technologies. In order to meet the technological requirements of the cutting objects, the heavy Industry factory has vigorously promoted plasma and laser cutting technologies in recent years. The proportion of plasma cutting and laser cutting equipment has reached about 70%. In addition, based on the maturity of cutting technologies at home and abroad, it selectively determines whether to purchase domestic or import the selected equipment.

4) In the manufacturing of construction machinery, a certain amount of small flame cutting and plasma cutting equipment should be selected to facilitate bevel processing and thin plate shaping. At the same time, consider adding bevel cutting function to the coordinate CNC cutting machine.

5) In the application of flame cutting, efforts should be made to vigorously promote the use of new industrial gases recommended by the state, and liquid oxygen should be used to replace bottled oxygen.

Xuzhou Heavy Industry Factory replaced oxygen-acetylene gas cutting with oxygen-propane gas cutting as early as the early 1990s. In recent years, it has carried out technological renovations of canned liquid oxygen and canned propane, which has greatly improved the cutting quality and efficiency, reduced safety hazards, saved costs and materials.

4. Conclusion

Today, with cutting technology flourishing everywhere, cutting equipment in the construction machinery manufacturing industry will no longer be the only one standing out. In recent years, the factory has developed a pattern where both small-scale cutting equipment and gantry-type CNC cutting equipment are available, and flame cutting technology is compatible with plasma and laser cutting technologies.

From the application of cutting technology in heavy factories, it can be seen that when selecting cutting technology and cutting equipment for construction machinery, the following aspects should be noted:

First of all, the processing object needs to be clearly defined. For instance: the material to be cut, its thickness, the particularity of the workpiece's process, etc. Additionally, it is necessary to understand the company's efficiency requirements for the selected equipment.

Secondly, it is necessary to understand the development and maturity of cutting technologies both at home and abroad, know the advantages and disadvantages of various cutting technologies, and analyze the comprehensive benefits.

Third, select the cutting technique and put forward special requirements.

Fourth, while promoting and applying advanced cutting technologies, efforts should be made to ensure environmental protection, safety, energy conservation and material conservation, and increase the promotion and application of related new technologies and new processes.