1 Introduction
Since ancient times, mankind has used the impact of water currents to make hydraulic machines such as waterwheels and water mills. If the water stream is ejected from the high pressure water gun, the impact force is greater. The former Soviet Union was used in the coal mining industry, and it is known as "hydraulic coal mining." The water jetted by the high speed is blocked by the coal seam, and the speed drops sharply. In the instant, there will be enough big impact force to make the coal seam brittle fracture and complete the coal mining operation. Inspired by this, former Soviet scientists have developed high-pressure water jet cutting technology, and U.S. companies have obtained patents for this technology to commercialize it. Water knife application industry is very broad, aviation, automotive, stone, ceramics, glass, metal, concrete and other industries, and with the maturity of the product and the application of the surface, ultra-high pressure CNC water cutting machine (waterjet) gradually enters A growth period, thanks to the rapid development of the machinery industry in recent years, relying on a more high-precision digital platform, can use waterjets for fine processing, and expand the scope of water cutting applications to the broader metal processing industry, Not only limited to the processing of materials such as glass, ceramics, and stone.
Taking metal cutting as an example, a variety of processing methods present a blossoming trend, including laser, flame cutting (plasma cutting), electric spark cutting, and wire cutting. Various cutting methods have their own advantages, and they all have certain limitations, each occupying a part of the market. However, in many cutting methods, water cutting belongs to a special kind of cold state cutting, directly using the kinetic energy of the abrasive water jet to cut the metal to achieve the purpose of cutting, there is no chemical change in the cutting process, and there is no physical and chemical properties of the cutting material Impact, no heat deformation, narrow slits, high precision, smooth surface, clean and pollution-free, can be processed by traditional methods can not be processed materials, such as glass, ceramics, composite materials, reflective materials, chemical fiber, heat-sensitive materials. The actual processing effect is shown in Figure 1.
Figure 1 actual processing effect
As people deepen their understanding of water cutting technology, the market is gradually recognizing the unique advantages of water cutting technology in the metal cutting industry. Laser cutting is used as an example for comparison. The speed and accuracy of laser cutting on thin metal sheets is better than that of water cutting. However, in general, it is difficult for lasers to cut metal sheets (especially non-ferrous metals) larger than 16 mm, and laser cutting materials. There is still a certain heat-affected zone in the periphery; the thickness of the waterjet cutting metal material can generally reach 50mm or more, and has no effect on the material. The finish of the cut metal is up to 1.6μm and the cutting accuracy is ±0.10mm, which can be used for precision forming and cutting. In addition, water cutting has unique features in the cutting of non-ferrous metals and stainless steel, no reflection effect and edge loss, plus waterjet cutting material without restrictions. Combining these factors, many users who chose lasers or other cutting tools in the early stages chose water cutting.
In the metal cutting industry, the pursuit of high-quality, high-efficiency direct forming processing is currently the mainstream development trend in the world. The “waterjet†cutting machine is in response to this demand and continues to innovate in related technology applications: Including precision ball screw, servo motor, resonant reduction unit and other technologies, the machine tool can achieve higher position accuracy, backlash compensation and repeat positioning accuracy. Therefore, the machine tool manufacturers have devoted more energy to the analysis of the causes of machine tool geometric errors. The accuracy of the machine tool has been detected by using high-precision measuring instruments such as a club measuring instrument and a laser interferometer, and an error map has been established to give accuracy corrections. In order to make high-precision machine tools. The selection, manufacturing process, and quality inspection methods of the parts and components of CNC machine tools are the guarantee for improving the accuracy and stability of CNC machine tools.
2 Process requirements
As the "waterjet" numerical control platform uses ball screw, rolling linear guide and other precision transmission technology, the control accuracy is within +0.02mm. At the same time, the focusing performance of nozzles and cutting heads with abrasive water jets and the technical breakthrough of long-life nozzle materials are matched with the continuous and smooth operation of high-power ultra-high pressure systems, and full-automatic sand supply, sand control, and high pressure water start and stop are applied. The control system allows the "waterjet" to cut and process automatically for 24 hours.
"Waterjet" also has powerful computer-aided design and control functions. It is automatically decelerated when cutting "corners and sharp corners", making the cutting surface smooth and smooth, and "waterjet" cutting has the characteristic of "grinding". The "waterjet" has greatly changed and improved in the cutting quality and efficiency, and can be directly used in forming and cutting of metal parts.
Here is an example of the application of Delta B2 servo in a single arm suspension girder CNC waterjet device. The following is introduced:
(1) Maximum movement speed of X and Y axes: 20 m/min, cutting speed: 0-8 m/min.
(2) Cutting accuracy: +/-0.1mm, Straightness: +/-0.1mm, Repeating positioning accuracy: ±0.05mm.
(3) XY roundness: <80um.
(4) The equipment operates with low noise and high response.
3 control system
3.1 Hardware Configuration
(1) Host computer: adopts DVP80EH00R2 PLC host
(2) Drive part: Adopt Delta B2 servo and motor. as shown in picture 2.
The specific model is: X-axis driver ASDA-B2-1021-B motor ECMA-C21310ES.
Y-axis driver ASDA-B2-1021-B Motor ECMA-C21310ES.
Figure 2 Delta B2 servo and motor
(3) Human-Machine Interface: HMI Devices Using DOP-B07S201
3.2 System Framework
The system framework is shown in Figure 3.
Figure 3 control system block diagram
Waterjet cutting machine control system uses Delta human-machine interface as the main station monitoring equipment, using human-machine interface DOP-B07S201 three RS232 communication ports. PLC host DVP80EH00R2 adopts RS232 communication port to connect with HMI equipment, and uses RS485 communication port to connect with two servo drivers ASDA-B2-1021-B. Servo driver controls servo motor via U, V, W port to control waterjet cutting machine. The X and Y axes operate. The man-machine interface sets the motor target speed and reads the actual motor speed. The PLC host simultaneously performs peripheral auxiliary related measurement actions through other auxiliary devices.
3.3 Reality of Control System
The real picture of the control system cabinet is shown in Figure 4.
Figure 4 real-time diagram of the control system cabinet
4 system technical points
4.1 System Benefits
(1) High response
Delta's B2 Servo's excellent high-speed performance: The speed response bandwidth is 550Hz, and the order time can be up to 1ms. Under no-load conditions, the rated speed -3000rpm to 3000rpm only takes 10ms to accelerate.
(2) High precision
Delta B2 servo adopts 17-bit (160,000p/rev) high-resolution encoder to meet the application requirements of high-precision positioning control and smooth and low-speed operation of the machine equipment. Accepts high-speed differential arterial wave commands (4Mpps) to achieve high-accuracy position control settings.
(3) Resonance suppression and low noise
When the response is high, there will be noise during operation. How to eliminate it? The B2 servo has a powerful auto-resonance suppression function that can achieve continuous resonance suppression, as well as suppression of up to three resonance points. This eliminates the hassle of vibration suppression by manually adjusting the parameters. For the cantilever beam structure, resonance is easy to occur, so with this feature, it brings great convenience to customers. The actual effect detected when applying Delta B2 servo actual machining is shown in Figure 5:
Figure 5 roundness test
The actual effect of the club test is used on the spot, and the roundness of 57.9um<80um fully meets the requirements of customers.
4.2 Servo gain adjustment
Use B2 automatic gain adjustment and manual adjustment.
Using Delta B2 Servo's powerful servo tuning software to facilitate gain adjustment and settings, see Figure 6.
Figure 6 Gain adjustment and setting software interface
5 Conclusion
Due to the cantilever's architecture, the center of gravity of the equipment during the operation is unstable, which in turn causes the mechanism's jitter and noise, and it is easy to produce poor finish. The use of Delta B2 servos for high performance, low noise, and automatic resonance suppression This solves this problem and is well-received by customers. Now it has been used very well in customers and has won the trust of customers. The application practice shows that the control system based on Delta servo products has stable performance, safety, reliability, and high cost performance, and is worthy of reference and promotion by the industry peers.
ã€references】
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[2] Choice and Application of Frequency Converter in Industry Liu Jideng et al. Science and Technology Information No. 23, 2009
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