Domestic products are very poor! And it's not durable. Not as good as foreign countries in the 1980 s and 1990 s.
network computer
Numerical control (numerical control for short) refers to controlling the operation of machinery and other devices with discrete digital information, which can only be programmed by the operator himself.
Day-Night Capability
Direct digital control
A system that directly controls and manages a group of NC machine tools to process or assemble parts with a general computer.
Computer Numerical Control (CNC)
Application of numerical control technology
The development of numerical control technology is quite rapid, which greatly improves the productivity of mold processing, and the CPU with faster operation speed is the core of the development of numerical control technology. The improvement of CPU is not only the improvement of operation speed, but also the improvement of numerical control technology in other aspects. It is precisely because of the great changes in numerical control technology in recent years that it is worth summarizing the application of numerical control technology in mold manufacturing at present.
The processing time of program blocks, etc., due to the improvement of CPU processing speed by CNC manufacturers and the application of high-speed CPU in highly integrated CNC systems, the performance of CNC has been significantly improved. Faster and more sensitive systems not only achieve higher program processing speed. In fact, a system that can process the machining program of parts at a fairly high speed may be like a low-speed machining system during operation, because even a fully functional CNC system has some potential problems, which may become the bottleneck limiting the machining speed.
At present, most mold factories are aware that high-speed machining needs more than short processing time. In many ways, this situation is similar to driving a racing car. Will the fastest car win the race? Even the occasional audience knows that there are many factors that affect the result of the game besides speed.
First of all, it is very important for the driver to know the track: he must know where there is a sharp turn, so that he can slow down properly and pass the corner safely and efficiently. In the process of machining dies at AG speed, the trajectory monitoring technology in CNC can obtain the information of sharp curves in advance and play the same role.
Similarly, the sensitivity of the actuator to other actuator actions and uncertainties is similar to the servo feedback times in numerical control. Servo feedback in CNC system mainly includes position feedback, speed feedback and current feedback.
When the driver is driving around the track, the consistency of action and whether he can brake and accelerate skillfully have a very important influence on the driver's on-the-spot performance. Similarly, the bell-type acceleration and deceleration and trajectory monitoring function of CNC system also uses slow acceleration and deceleration instead of sudden speed change to ensure the smooth acceleration of machine tools.
In addition, there are other similarities between racing cars and CNC systems. The power of racing engine is similar to that of numerical control driving device and motor, and the weight of racing car can be compared with that of moving parts in machine tools, and the rigidity and strength of racing car are similar to that of machine tools. The ability of CNC to correct specific path errors is very similar to the ability of drivers to control cars in the driveway.
Another situation similar to CNC now is that those cars that are not the fastest often need drivers with comprehensive skills. In the past, only high-grade CNC can ensure high machining accuracy while cutting at high speed. Now the function of middle and low-grade CNC may also be successfully completed. Although the high-grade CNC is the best available at present, it is also possible that the low-grade CNC you use has the same processing characteristics as the high-grade CNC of similar products. In the past, numerical control was the factor limiting the highest feed speed of die processing, but today it is the mechanical structure of machine tools. Even the best numerical control will not improve the performance when the machine tool is already at the performance limit.
Inherent characteristics of numerical control system
The following are some basic CNC features in the current mold machining process:
1. NURBS interpolation of curves and surfaces
This technique uses interpolation along the curve instead of a series of short straight lines to fit the curve. The application of this technology has been quite common. At present, CAM software used in many mold industries provides an option, which is to generate parts programs in NURBS interpolation format. At the same time, the powerful CNC also provides five-axis interpolation function and related characteristics. These characteristics improve the quality of surface machining, the smoothness of motor operation, the cutting speed and the machining procedure of parts.
2. Smaller instruction units
Most CNC systems transmit motion and positioning instructions to the machine tool spindle in units of not less than 1 micron. After taking full advantage of the processing power of CPU, the minimum instruction unit of some CNC systems can even reach 1 nm (0.00000 1mm). After the instruction unit is reduced by 1000 times, higher machining accuracy can be obtained and the motor runs more smoothly. The smooth operation of the motor enables some machine tools to run at higher acceleration without increasing the vibration of the bed.
3. Bell curve acceleration/deceleration
Also called S-curve acceleration/deceleration or creep control. Compared with the linear acceleration method, this method can make the machine tool get better acceleration effect. Compared with other acceleration modes (including linear mode and exponential mode), bell curve mode can obtain smaller positioning error.
4. Tracking monitoring to be handled
This technology has been widely used, and it has many differences in performance, which distinguishes its working mode in low-level control system from that in high-level control system. Generally speaking, CNC preprocesses the program by monitoring the machining trajectory, thus ensuring better acceleration and deceleration control. According to the performance of different CNC, the number of program blocks needed to monitor the machining trajectory varies from two to hundreds, which mainly depends on the shortest machining time and acceleration and deceleration time constants of the part program. Generally speaking, in order to meet the processing requirements, at least fifteen trajectory monitoring programs need to be processed.
5. Digital servo control
The development of digital servo system is so rapid that most machine tool manufacturers choose this system as the servo control system of machine tools. After using this system, CNC can control the servo system in time, and CNC can control the machine tool more accurately.
The functions of the digital servo system are as follows:
1) will increase the sampling speed of the current loop, and with the improvement of the current loop control, the temperature rise of the motor will be reduced. This can not only prolong the life of the motor, but also reduce the heat transferred to the ball screw, thus improving the accuracy of the screw. In addition, the acceleration of sampling speed can also improve the gain of speed loop, which is helpful to improve the overall performance of machine tools.
2) Because many new CNC systems use high-speed sequences to connect with servo loops, CNC can get more information about the operation of motors and drivers through communication links. This can improve the maintenance performance of machine tools.
3) Continuous position feedback allows high-precision machining under high-speed feed. The acceleration of numerical control operation speed makes the speed of position feedback become the bottleneck restricting the operation speed of machine tools. In the traditional feedback mode, with the change of sampling speed of CNC and external encoder of electronic equipment, the feedback speed is limited by the signal type. Using serial feedback, this problem will be solved well. Even if the machine tool runs at high speed, it can achieve accurate feedback accuracy.
6. Linear motor
In recent years, the working performance and popularity of linear motors have been significantly improved, so many machining centers have adopted this device. So far, Fanuc has installed at least 1000 linear motors. Some advanced technologies of GE Fanuc make the maximum output force of linear motor on machine tool 15500n and the maximum acceleration 30g. The application of other advanced technologies reduces the size and weight of machine tools and greatly improves the cooling efficiency. All these technological advances make linear motors have stronger advantages than rotary motors: higher acceleration and deceleration; More accurate positioning control, higher rigidity; Higher reliability; Internal dynamic braking.
External additional functions: open CNC system
Open CNC machine tools have developed rapidly. At present, the communication speed of available communication systems is relatively high, so there are many types of open CNC structures. Most open systems combine the openness of standard PC with the functions of traditional CNC. The biggest advantage of this is that even if the hardware of the machine tool is outdated, open CNC still allows its performance to change with the existing technology and processing requirements. With the help of other software, other functions can be added to the open CNC system. These properties can be closely related to mold processing, but they also have little to do with mold processing. Usually, the open CNC system used in the mold workshop has the following common function choices:
Low cost network communication;
Ethernet;
Adaptive control function;
An interface for connecting a barcode reader, a cutter serial number reader and/or a pallet serial number system;
The function of saving and editing a large number of parts programs;
The stored program controls the collection of information;
File processing function;
Integration of CAD/CAM technology and workshop planning;
Universal operation interface.
The last point is extremely important. Because the demand for CNC with simple operation is increasing in mold processing. In this concept, the most important thing is that different CNC have the same operation interface. Generally speaking, operators of different machine tools must be trained separately, because different types of machine tools and machines produced by different manufacturers use different CNC interfaces. Open CNC system creates opportunities for the whole workshop to use the same CNC control interface.
Now, even if the machine tool owner doesn't know C language, he can design his own interface for numerical control operation. In addition, the controller of the open system allows different machine operation modes to be set according to individual needs. In this way, operators, programmers and maintenance personnel can set up according to their own requirements. When using, only the specific information they need is displayed on the screen. This can reduce unnecessary page display and simplify CNC operation.
Five-axis machining
In the process of manufacturing complex molds, five-axis machining is more and more widely used. By using five-axis machining, the number of tools or/and machine tools required for machining parts can be reduced, and the number of equipment required in the machining process will be minimized, and at the same time, the total machining time will be reduced. The function of numerical control is getting stronger and stronger, which enables numerical control manufacturers to provide more five-axis functions.
In the past, only high-grade CNC had functions, but now it is also available in mid-range products. For those manufacturers who have never used five-axis machining technology, the application of these characteristics makes five-axis machining easier. The current numerical control technology is applied to five-axis machining, which makes five-axis machining have the following advantages:
Reduce the need for special tools;
Allow setting tool offset after completing the part program;
Support the design of general program, so that the post-processing program can be used interchangeably between different machine tools;
Improve the finishing quality;
It can be used for machine tools with different structures, so it is not necessary to explain whether the spindle or the workpiece is rotating around the center point in the program. Because this will be solved by CNC parameters.
We can use the compensation example of spherical milling cutter to explain why five-axis is particularly suitable for die processing. In order to accurately compensate the deviation of the spherical milling cutter when the parts and the cutter rotate around the central pivot, CNC must be able to dynamically adjust the compensation amount of the cutter in X, Y and Z directions. Ensuring the continuity of tool contact points is beneficial to improve the finishing quality.
In addition, the use of five-axis CNC is also manifested in the characteristics related to the rotation of tools around the spindle, the characteristics related to the rotation of parts around the spindle, and the characteristics that allow operators to manually change the tool vector.
When the central axis of the tool is used as the rotation axis, the original tool length deviation in the Z-axis direction will be divided into three components: X, Y and Z ... In addition, the original tool diameter deviation in the X-axis and Y-axis will also be divided into three components in the X-axis, Y-axis and Z-axis. Because in cutting engineering, the tool can move in the direction of the rotation axis, all these offsets must be updated dynamically to explain the changing direction of the tool.
Another function of CNC is called "Tool Center Programming", which allows programmers to define the tool path and center speed. CNC ensures that the tool moves according to the program through the command of rotating axis and linear axis direction. This feature makes the center point of the tool no longer change with the change of the tool, that is to say, the offset of the tool can be directly input in five-axis machining as in three-axis machining, and the change of the tool length can be explained by post-processing again. The motion characteristics of the rotating shaft are realized by rotating the spindle, which simplifies the post-processing of tool programming.
Using the same function, the workpiece rotates around the central fulcrum, and the machine tool can also obtain rotary motion. The newly developed CNC can dynamically adjust the fixed offset and rotating coordinate axis to match the movement of parts. The numerical control system also plays an important role when the operator realizes the slow feed of the machine tool manually. The newly developed CNC system also allows the shaft to feed slowly along the direction of the tool vector, and also allows the direction of the tool vector to be changed without changing the position of the tool tip (see the above figure).
These characteristics make it easy for operators to use 3+2 programming method widely used in mold industry when using five-axis machining machine tools. However, with the gradual development of the new five-axis machining function and the acceptance of this function one by one, the real five-axis mold machining machine tool may become more common.