Three dimensional five axis fiber laser cutting machine tool is regarded as the pearl on the crown of high-power laser processing equipment. It is mainly used for cutting holes and trimming 3D special-shaped surfaces, replacing punching die and trimming die. In the early days, manual plasma cutting of 3D workpieces was adopted in China, and the cutting effect was not ideal. In recent years, the robot 3D laser cutting machine has been developed in China, and the cutting effect has been improved to a certain extent. However, due to the low accuracy of the robot, the cutting accuracy is not high, and it has only been applied in some industries with low requirements. In the automotive stamping die industry, the pilot test requires high cutting accuracy. The three-dimensional five axis optical fiber laser cutting machine is popular because of its high production efficiency and stable performance. The product diagram of three-dimensional five axis optical fiber laser cutting machine is shown in Figure 1.

Optical fiber laser cutting machine

Optical fiber laser cutting machine

Fig. 1 Three dimensional five axis optical fiber laser cutting machine

1、 Technical development background

Three dimensional five axis optical fiber laser cutting machine is a high-end machine tool equipment integrating light, machinery, electricity and gas. It is used in the automotive industry, mold industry, military industry, aerospace industry, household appliances industry and special-shaped pipe cutting, mainly for metal cutting of curved sheet.

Three dimensional and five axis laser cutting technology has been developed since the 1990s. There are only two manufacturers, Trumpf of Germany and Prima of Italy, which basically monopolize the market. After 2008, NTC and Mitsubishi of Japan developed a mobile 3D five axis CO2 laser cutting machine with low acceleration, low speed and high accuracy. However, for a long time, the 3D five axis laser cutting machine is mainly used for research and development and small batch trial production. It can trim and cut holes on the 3D parts formed by stamping, replace the traditional trimming and punching dies, shorten the development cycle of new products, and reduce manufacturing costs. Therefore, the annual market sales are small. In the Chinese market, the market demand is generally about 30-40 sets a year.

However, due to the emergence and application of automobile hot forming technology, the situation of low market demand has changed. An automobile hot forming production line is generally equipped with 4-5 three-dimensional five axis laser cutting machines, and the market demand is developing explosively. Up to now, there are nearly 450 automobile hot forming production lines in the world, and there are about 2000 sets of three-dimensional five axis laser cutting machines following the supporting production. There are nearly 170 hot forming production lines in China, and there are about 700 sets of three-dimensional five axis laser cutting machines following the supporting production.

The hot forming technology of steel plate refers to that the steel plate is formed once after being heated at 950 ℃, and then cooled rapidly, so as to comprehensively improve the strength of the steel plate. The yield strength reaches above 1000Mpa. After being used on the vehicle body, the vehicle weight does not increase, but the bearing capacity is increased by 30%, and the safety performance is significantly improved. Due to the high strength of the steel plate, the traditional trimming die and punching die can not trim and punch due to the high strength of the steel plate, and can only use laser for production, so that three-dimensional five axis laser cutting products enter the automobile batch production line, becoming an irreplaceable production process and process.

The yield strength of ordinary steel plate is 140Mpa, which is suitable for sightseeing buses and cable cars; The yield strength of high-strength steel plate is 180-240Mpa, which is applicable to trucks, forklifts, buses, excavators, agricultural machinery, etc; The yield strength of high-strength steel plate is 260-320Mpa, which is suitable for economical cars and SUVs; The yield strength of the super strength steel plate is 340-700Mpa, which is suitable for high-end cars and SUVs; However, the yield strength of hot formed steel plate exceeds 1000Mpa, and generally the yield strength of hot formed steel plate is about 1500Mpa. At present, material manufacturers are developing hot formed steel plates with a yield strength of about 2000Mpa. More and more ultra-high strength steel plates are widely used in the automotive industry, which makes 3D five axis laser cutting machine products more and more widely used.

2、 Technology development status

At present, the main manufacturers of 3D five axis laser cutting machines are Trumpf of Germany, Prima of Italy, NTC of Japan, Mitsubishi and Han's Laser of China. Trumpf and Prima have been produced earlier, their products are mature, their performance is stable, and they are highly recognized by customers in the market. NTC and Mitsubishi of Japan only produce three-dimensional five axis CO2 laser cutting machine with low speed and low acceleration, which has low production efficiency and high energy consumption (CO2 laser has very high energy consumption compared with fiber laser), unable to meet the requirements of production efficiency of automobile hot forming production line. Han's Laser has broken through the key technologies and mastered the core technologies. It not only produces low speed and high-precision three-dimensional five axis fiber laser cutting machine, but also produces high-speed and high-precision three-dimensional five axis fiber laser cutting machine. Its technology closely follows Trumpf and Prima, becoming a product with high cost performance ratio in the current market for three-dimensional five axis fiber laser cutting. It has solved the key core technologies of three-dimensional five axis fiber laser cutting machine:

1. Machine tool structure optimization design and dynamic design

Carry out CAE finite element analysis on the structure of the whole machine, and analyze the dynamic and static stiffness, static strength, and thermal characteristics to obtain the best stiffness field and temperature field of the whole machine. After repeated testing and verification, carry out design improvement, analyze the factors that make the theoretical value different from the actual test value data. When the theoretical value is basically consistent with the actual test value data, finally obtain the economic and lightweight structural design of the whole machine. Machine tool structure optimization design and dynamic design block diagram.

2. Improve dynamic performance and stability

CAE finite element modal analysis is carried out for components with high speed, large inertia and large size. The damping, local stiffness and mass distribution of the joint surface are analyzed. Vibration isolation, vibration reduction and vibration suppression measures are taken to improve and optimize the design of the structure. Through repeated testing and verification, mobile components with good dynamic performance and stability are obtained to ensure the dynamic performance and stability of the product. Block diagram and modal analysis diagram for improving dynamic performance and stability.

3. Improve high-speed and high-precision positioning

Test and finite element analysis of the motor and servo feed drive system, analyze and optimize the positioning accuracy, response speed, thermal characteristics and motor rigidity, and analyze the tracking characteristics to compensate the error of the multi axis linkage of the CNC system, so as to obtain high speed and high-precision positioning. Analysis of servo drive system.

4. Solve the core technology of infinite rotation 3D cutting head

Precise optical calculation, formulation of spatial algorithm of system geometry, development of 360 ° wireless rotary 3D cutting head, independent innovation, with core technology, is the fourth manufacturer capable of producing 360 ° wireless rotary 3D cutting head after Trumpf of Germany, Prima of Italy, and LT of Germany, breaking the foreign technology monopoly. 360 ° wireless rotation of three-dimensional five axis cutting head.

For 3D five axis cutting head products, solve the following key and core technologies:

(1) Sealing of Water, Gas and Light Paths of 3D Five axis Infinitely Rotating Cutting Head

The motion track of the 3D five axis cutting head is relatively complex during processing. The pipes transmitted through the mechanical transmission part of the C-axis (infinite rotation) have optical path, water path, gas path, and electrical signal path. As the C-axis is an infinitely rotating structure, the above channels cannot adopt a pipe type structure, so a specific rotating channel structure needs to be designed for transmission. The following problem is to solve the dynamic sealing of water, gas and light in the moving channel. In order to break through this major obstacle, the rotating machinery structure with independent transmission of water, gas, light and electricity channels is selected from a variety of alternative design schemes; According to the technical requirements of sealing elements for each rotating transmission channel of the C-axis, a rotating channel sealing element based on new materials is developed. The element design fully considers the balance of comprehensive factors such as wear resistance, sealing performance and dynamic friction between the element and the pipeline; With the guidance of theory and experience, the tolerance fit between the sealing element and the sealed channel is adjusted properly, and the high-speed infinite rotation C-axis component integrating multiple sealed transmission channels is successfully realized. Through a large number of experiments, it has been verified that the performance of the self-developed high-speed rotary sealing element has reached the level of similar foreign products.

(2) Anti interference Shielding Technology of Electrical Signal under High Speed Rotation of 3D Cutting Head

When traditional cables are used to transmit electrical signals in the rotating axis, the cables will be wound or even pulled to break due to the rotation of the axis. When multiple electrical signals are transmitted simultaneously in a space with small spacing, there will be a risk of signal crosstalk. In order to avoid such problems and ensure the anti electromagnetic interference transmission of multi-channel electrical signals, according to the technical specifications of multi-channel electrical signal channels, the unique electric slip ring structure design was pioneered to break through the anti-interference transmission of multi-channel electrical signals on high-speed rotating shafts.

5. Online software modification technology

Han's self-developed HANS 3DEDIT online modification program software makes it more convenient and fast to modify the program size and change parts quickly, improving production efficiency and saving production costs. The online modification software is shown in Figure 7.

6. Research on integrated application technology based on CNC three-dimensional five axis optical fiber cutting system with RTCP function

(1) Research the hardware integration system structure of 3D five axis fiber laser cutting equipment, analyze the software and hardware interfaces of the CNC system with RTCP function, and design the system integration control scheme of each processing component in 3D five axis fiber laser cutting.

(2) Study RTCP functional data. Three dimensional five axis fiber laser cutting system consists of three functional blocks, namely, processing control module, offline programming module and laser cutting process database. Combined with the hardware integration of the processing equipment, the secondary development of software for the three-dimensional five axis fiber laser cutting process is given to the PC industrial control platform to design the NC system control functions, develop the three-dimensional five axis fiber laser cutting control application program interface, and realize the three-dimensional five axis fiber laser cutting machine motion control and process adjustment functions.

(3) Based on 3D space mapping, the kinematics of 3D five axis laser machine tool is analyzed, and the cutting head motion simulation is designed.

(4) Develop the database of PC platform based on HMI, and use SQL to design the specific functions of the database according to the functional requirements, so as to realize the functions of database modification, addition, query, browsing and deletion.

7. Research on laser cutting technology for 3D complex surfaces

(1) Analyze the external optical path mode, conduct shaping compensation for the optical path, ensure the best cutting beam mode, and develop a special process control software for three-dimensional five axis laser cutting.

(2) Research and develop the fast piercing and cutting state control feedback technology, and develop the process methods such as sharp corner cutting of thick carbon steel plate, limit cutting of small holes of thick plate, high power optical fiber nitrogen cutting of medium and thin carbon steel, complex graphics and picture processing and application, so as to overcome the technological problems of complex graphics and small contour processing.

(3) The control method of laser cutting, the control method of laser cutting speed and the laser cutting method of turning angle are studied. The methods of error compensation, corner cutting quality control and sharp corner cutting quality control of 3D panel are studied.

(4) Develop Z-axis profiling control technology based on CC compilation cycle, graphic preview and track synchronization display technology, flexible intervention and flexible patching technology based on graphic preview, and real-time slope adjustment technology of laser pulse frequency and duty cycle and laser power based on fast response laser pulse square wave PWM generator.

Solve the technological problems such as corner overburn of 3D parts, sharp corner overmelting of thick plates, limit small hole cutting, and rapid piercing of thin plates, establish a perfect database of laser cutting process experts, and realize the automatic call of laser cutting process parameters such as large contour, small contour, corner, and standard graphics.

3、 Technology and application development trend

1. Technology development trend

With the 3D five axis laser cutting technology becoming more and more advanced and advanced, the performance and functions are becoming more and more powerful. The technical development trends are as follows:

(1) High acceleration, high speed: the product acceleration is getting higher and higher, the product speed is getting faster and faster, and the production efficiency is getting higher and higher;

(2) High cutting speed, high precision: high cutting speed, high production efficiency and low production cost; Only high positioning speed and high repeated positioning accuracy can we have high cutting accuracy and meet the increasing demand for product quality;

(3) Automation and intelligence: the labor cost is increasing, and the products need to be developed in the direction of high automation and high intelligence; On the one hand, high automation can reduce manpower and save costs; On the other hand, high intelligence makes machine equipment technology easy to operate, less dependent on personnel technology, simple and easy to learn, and can also reduce costs.

2. Application development trend

On the one hand, the continuous optimization and improvement of product performance and the continuous decline of product price have made it affordable for more and more users. Basically, three-dimensional and five axis laser cutting processes can be used, giving priority to traditional processing methods.

On the other hand, 3D five axis laser cutting technology promotes personalized design of products. Engineering designers can give play to personalized design and design more beautiful products, which are no longer restricted by traditional processing methods.

Moreover, the hot forming technology has entered the automobile industry, which has made the 3D five axis laser cutting machine an irreplaceable process in the automobile production process. As more and more models adopt the hot forming technology, more and more 3D five axis laser cutting machines enter the automobile production line. At present, only high-end vehicles are used, but with the development of technology, economic vehicles and new energy vehicles will also use hot forming technology. According to the research and analysis of the automobile industry, the upgrading of automobiles will be faster in the future, and the past era when millions of models were produced has become history. The number of single models is gradually decreasing, and the cost of the mold is very high. The three-dimensional five axis laser cutting machine will reflect the lower use cost to meet the development needs of the times.

To sum up, in the automotive industry, especially in the automotive hot forming industry, with the continuous application and development of three-dimensional five axis laser cutting, the level of automotive manufacturing technology is becoming more and more advanced, and the production efficiency is getting higher and higher. It can not only solve the problem of high strength steel for automotive hot forming, but also promote the development of automotive personalized design.