Abstract: This article mainly introduces the use of Delta VE inverters in CNC machining centers.
Keywords: CNC machining center positioning VE frequency converter station pulse given
1 Introduction
CNC machine tools are the key equipment for modern manufacturing. The production and technical level of a national CNC machine tool to some extent represent the country's manufacturing level and competitiveness. There is still a big gap between the technical level, performance and quality of CNC machine tools in China and foreign products. Most high-performance machining centers and functional components rely on imports. The machining center is a concentrated expression of numerical control technology. The active market and strong demand have become the forefront of the current and future competition in the CNC machine tool market.
The machining center is a digital control machine tool that has a magazine and can automatically change tools and perform multi-step machining on the workpiece. After the workpiece is clamped once, the digital control system can control the machine tool to automatically select and change the tool according to different processes, and automatically change the spindle speed, feed amount, tool trajectory of the workpiece relative to the workpiece, and other auxiliary functions. Multi-process processing. Due to the concentration of processes and automatic tool change, the machining center reduces the time for workpiece clamping, measurement, and machine tool adjustment, so that the cutting time of the machine tool can reach 80% of the machine's starting time (ordinary machine tools only 15 to 20%); It also reduces the workpiece turnover, handling and storage time between processes, shortens the production cycle, and has significant economic benefits. The machining center is suitable for medium and small batch production with complex part shapes, high precision requirements, and frequent product replacement. The first machining center was first developed in 1958 by the United States Carney-Treck. It adds automatic tool changer on the basis of CNC horizontal boring and milling machine, so that the workpiece can be milled, drilled, boring, reaming, tapping and other processes in one process after one clamping. Since the 1970s, the machining center has been rapidly developed, and an interchangeable headstock machining center has emerged. It has a number of multi-axle headstocks with tools that can be automatically replaced, and can simultaneously perform porous processing on workpieces. This type of multi-process centralized processing has also been extended to other types of CNC machine tools, such as turning centers. It is equipped with multiple automatic tool changing devices on CNC lathes and can control more than three coordinates. In addition to turning, the spindle can be stopped. Or indexing, and the tool rotation for milling, drilling, reaming and tapping processes, suitable for machining complex rotating parts. The machining center is divided into vertical and horizontal types according to the arrangement of the main shaft. Horizontal machining centers generally have indexing turrets or numerically controlled turrets, which can machine the sides of the workpiece; they can also be used for joint movements of multiple coordinates in order to process complex space surfaces. Vertical machining centers generally do not have a turntable and are only used for top surface machining. In addition, there are compound machining centers with two main shafts, vertical and horizontal, and vertical and horizontal adjustable machining centers whose main shafts can be adjusted to horizontal or vertical shafts. They can perform five-face machining of workpieces. The automatic tool changer of the machining center consists of a tool magazine and a tool changer for storing tools. There are many kinds of magazines, and there are two kinds of magazines and chains. Chain knife stocks have a large capacity. The tool changing mechanism exchanges tools between the spindle and the tool magazine of the machine tool. Commonly, robots are used. There are also spindles and tool magazines that exchange tools without a robot arm. The armless tool changer is called. To further reduce the non-cutting time, some machining centers are equipped with two pallets that automatically exchange workpieces. One carries the workpiece on the workbench and the other loads and unloads the workpiece outside the workbench. After the machine tool completes the machining cycle, the pallets are automatically exchanged so that the loading and unloading work pieces coincide with the machining time.
2 CNC machine tool spindle drive
The spindle drive system is a high-power actuator for CNC machine tools. Its function is to accept the S code speed command of the CNC system and the M code auxiliary function command to drive the spindle for machining. Spindle drive can use AC frequency conversion or AC servo two kinds of control methods, general AC frequency conversion spindle can be infinitely variable but can not be quasi-stop, need to install a spindle position sensor, with the CNC system PMC (index control system built-in PLC) logic The program completes the quasi-stop speed control and positioning stop; the AC servo spindle itself has an exact stop function, its own axis control PLC signal can be directly connected to the PMC of the CNC system, and the quasi-stop positioning control can be accomplished with the simple PMC logic program. And the control precision of the latter is much higher than the former, so the spindle drive system of most machining centers currently adopts AC servo spindles. With reference to the functions of the AC servo spindle, Delta developed a new generation of AC variable frequency drives - VE inverters, in addition to full functionality and performance comparable to AC servos, but also has strong versatility and price advantages through multiple Tests won the recognition and love of customers.
3 Delta VE frequency conversion spindle drive system
3.1 System Design Requirements
(1) Numerical control characteristics of the function and performance of the VE series inverter. The project customers are well-known companies in the CNC machining center. Combining the requirements of customers and the characteristics of the machining center, Delta's high-performance inverter--VE series inverters developed specifically for CNC machining centers are ideally suited for use in CNC machining centers.
· Fast point positioning can be achieved through external I/O points. There are special parameters to adjust the characteristics of the positioning curve and positioning time, set to facilitate the implementation;
·The realization of rapid acceleration and deceleration through the adjustment of special parameters;
· The new PDFF control makes the adjustment of gain more simple and convenient and easy to master;
· Accept analog signals and pulse signals, more comprehensive support for the host computer.
(2) Test machining center configuration:
· CNC system: Taiwan's new generation of numerical control system SYNTEC 9401;
·Spindle specification: Wuxi Bohua Motor 8kw/maximum frequency 600hz-12000rpm/6P/380V/450hz/25A, encoder +5V/GND/+A/-A/+B/-B/+Z/-Z/512ppr ;
·Inverter specification: 075V43A-2+EMV-PG01L, software version 9.98 Beta, braking resistor 1500W/75ohm.
3.2 spindle frequency conversion system design
(1) Inverter electrical design: See Figure 1.
Figure 1 Inverter wiring diagram
3.3 Frequency Converter Parameter Design Procedure
(1) Set the motor parameters to the inverter for dynamic self-tuning of the motor. To use the high performance of the VE series inverter, accurate motor parameters are the basis. First fill in the basic parameters to the relevant position of the inverter:
And use the above parameters for VF control operation, the specific situation is as follows, after observing the motor performance characteristics.
(2) Solve an interesting engineering problem. In the above data, the motor rated speed 05-03 is not provided by the motor manufacturer's nameplate, and it is not clear what the motor manufacturer asks. In this case, because the motor itself has an encoder, through the VF control, the inverter will run to 450hz, observe the r status provided in the inverter, the actual speed of the motor is about 8900rpm, and the measured data will be filled in to 05-03. The rated current of the motor 25A, 075V43A-2 inverter is only 18A, so the rated current of the motor can only be adjusted to the maximum (21.6A maximum) as much as possible to fill in the 05-01 parameter.
Set parameter 5-00=1, and then press panel "RUN" for dynamic tuning.
After setting the motor parameters are
The 11-01 parameter relates to the encoder direction selection. If the setting is incorrect, the PG closed-loop control will have problems. The correct setting of 11-01 can be observed in the inverter panel r status. If r is a positive value, the direction setting is correct. If it is a negative value, the direction setting is reversed.
(3) Change the control mode to foc+pg and adjust the maximum operating frequency and acceleration/deceleration time
Use the panel to run. First, if F=550, after running, it is found that regardless of the start-up process or the stop process, when the output frequency reaches around 450 Hz, it does not change according to the acceleration/deceleration time, and the change is very slow. When the above phenomenon occurs, it can be solved by adjusting parameter 11-05 (M1IdsRef Limit). After 11-05 is changed from the factory value of 90 to 110, the acceleration and deceleration process is normal.
Figure 2 (F=590, 11-05=180) Acceleration Curve
(4) Inertia estimation and ASR automatic adjustment. The parameters 11-00=2, F=200HZ, 01-12=01-13=1, after the positive and negative rotations, the measured inertia parameter is 49. After that, 11-01=1 will be used to observe the rigidity of the motor and make the corresponding parameters. modify.
(5) External I/O function settings:
Referring to Fig. 1, MI1 is single-point positioning, MI2 is the first/second acceleration/deceleration time switch, and MI3 is the pulse position command input enable for single-point positioning. FWD/MI1 is closed and the inverter performs positioning action. The following parameters are related to the sensitivity of positioning and the stopping position during positioning. When adjusting the position, the spindle can be stopped at the position where it needs to be positioned and the G status value on the panel can be observed. When the position is correct, the observed G value is filled in. In 10-19, the sensitivity of the positioning process is changed by adjusting 10-21/10-22. The larger the 10-21, the smaller the 10-22, the faster the response, and the shorter the positioning process; the smaller the 10-21, 10 The larger -22, the slower the response and the longer the positioning process.
Current pulse control provides two modes: speed mode and position mode. When working in the speed mode, only need to set the frequency source signal as pulse reference, and set the given mode according to the pulse signal provided by the host computer; if the inverter needs to work in the pulse position command mode, in addition to the parameters needed in the speed mode In addition to the settings, the external terminal signal FWD/MI1/MI2/MI3 must also be closed.
3.4 Pulse Input Control of VE Series Inverter
VE series inverter supports two pulse input modes: 1. A/B phase pulse input; 2. Pulse + direction input. Since the new system provides a pulse + direction output method, you can choose the third or fourth mode as shown in Figure 3; then make the final correct choice based on the direction.
Figure 3 Pulse input method accepted
When using pulse control, there are also two more important parameters: 1.10-17PG electronic gear A; 2.10-18PG electronic gear B. The formula for calculation is speed=pulse frequency/number of encoder points (10-00)*electronic gear A/electronic gear B.
3.5 Acceleration and deceleration
Acceleration and deceleration characteristics of the test, the first adjustment of the protection function:
1-12=1,1-13=5,F=590
The accelerating time during accelerating from 0 to 590hz is 1.4s, and the maximum current during acceleration is 19.3A. See Figure 4 for the graph.
Figure 4 Acceleration curve
1-12=5, 1-13=5, F=590
The measured deceleration time during deceleration from 590hz to 0hz is 5.1s, and the maximum bus voltage during deceleration is 740VDC. The graph is shown in Figure 5.
Figure 5 Acceleration and deceleration curves
4 Conclusion
CNC machining centers have high control requirements for the spindles. Firstly, it is required to achieve a wide-range continuously variable transmission on the basis of high torque and strong overload capacity, and secondly, it is required to achieve a fixed-angle stop (ie, a quasi-stop) in the automatic tool change action. The machining center spindle drive system is more difficult than the general frequency control system or the low-power AC servo system in circuit design and operation parameter setting. The acceleration and deceleration characteristics and positioning functions of the numerical control spindle frequency conversion drive project based on Delta VE series high-performance frequency converters are fully able to meet the requirements of the machining center, and the cost performance is outstanding.