1. Different definitions
In simple terms, a CNC lathe is a machine tool controlled by numbers. This is an automated machine tool with program automation control. The entire system can logically process the program specified by the control code or other symbolic instructions, and then They carry out automatic compilation, and then carry out a comprehensive compilation, so that the movements of the entire machine tool can be processed in accordance with the original program.
The operation and monitoring of the CNC lathe, which is the control unit of this CNC lathe, is all done in the CNC unit, which is equivalent to the brain of a device. The equipment we usually talk about is mainly the machining center of the index-controlled lathe.
Ordinary lathes are horizontal lathes that can process multiple types of workpieces such as shafts, disks, rings, etc., and are often used to process the internal and external rotating surfaces, end faces, and various internal and external threads of the workpiece. Corresponding tools and accessories are used. Drilling, reaming, tapping, knurling, etc.
2. The scope is different
Numerical control lathes are not just a numerical control system, they also have many different technologies, and they use some different technologies. They cover a wide range.
Including CNC lathes, CNC milling machines, CNC machining centers, as well as CNC wire cutting and many other different types. Such a technology is to use digital programming language symbols to transform, and then process the entire computer-controlled machine tool.
3. Different advantages
Relatively speaking, there are many advantages to using CNC lathes to process products and general machine tools. Using CNC lathes to process products can greatly improve production efficiency. After the entire workpiece is clamped, input the programmed processing program.
The entire machine tool can automatically complete the processing process. Relatively speaking, when the processed parts are changed, usually only a series of CNC programs need to be changed. Therefore, to a certain extent, this can greatly shorten the entire processing time. Compared with the machining of the machine tool, it can improve the production efficiency the highest.
CNC lathe is one of the most widely used CNC machine tools. It is mainly used for cutting inner and outer cylindrical surfaces of shaft parts or disc parts, inner and outer conical surfaces with arbitrary cone angles, complex rotating inner and outer curved surfaces, cylinders, and conical threads. It can also perform grooving, drilling, reaming, and reaming. Hole and boring etc.
The CNC machine tool automatically processes the processed parts according to the pre-programmed processing program. We compile the machining process route, process parameters, tool motion trajectory, displacement, cutting parameters and auxiliary functions of the parts into a machining program list according to the instruction code and program format specified by the CNC machine tool, and then record the contents of the program list On the control medium, it is then input into the numerical control device of the numerical control machine tool to direct the machine tool to process the parts.
●High processing precision and stable processing quality;
●Multi-coordinate linkage can be carried out, and parts with complex shapes can be processed;
●When machining parts change, generally only need to change the numerical control program, which can save production preparation time;
●The machine tool itself has high precision and high rigidity, can choose a favorable processing amount, and has high productivity (generally 3~5 times of ordinary machine tools);
●The machine tool has a high degree of automation, which can reduce labor intensity;
●Higher requirements for the quality of operators and higher technical requirements for maintenance personnel.
Determine the process requirements of typical parts and the batch of processed workpieces. The function that the CNC lathe should have is to make preparations and the prerequisite for a reasonable selection of CNC lathes: meet the process requirements of typical parts.
The process requirements of typical parts are mainly the structural size, processing range and accuracy requirements of the parts. According to the accuracy requirements, that is, the dimensional accuracy, positioning accuracy and surface roughness of the workpiece, the control accuracy of the CNC lathe is selected. Choose based on reliability. Reliability is a guarantee for improving product quality and production efficiency. The reliability of a CNC machine tool means that the machine tool runs stably for a long time without failure when it performs its functions under specified conditions. That is, the mean time between failures is long, even if there is a failure, it can be restored in a short time and put into use again. Choose machine tools with reasonable structure, well-manufactured, and mass-produced machines. Generally, the more users, the higher the reliability of the CNC system.
Machine tool accessories, spare parts and their supply capacity, cutting tools, are very important for CNC lathes and turning centers that have been put into production. When choosing a machine tool, carefully consider the compatibility of tools and accessories.
Manufacturers generally choose products from the same manufacturer, and at least buy the control system of the same manufacturer, which brings great convenience to the maintenance work. Teaching units require students to be knowledgeable and knowledgeable, so it is a wise choice to choose different systems and to equip them with various simulation software.
Performance and price ratio to choose
Make sure that the functions and accuracy are not idle, not wasted, and do not choose functions that have nothing to do with your own needs.
Protection of machine tools
When needed, the machine tool can be equipped with fully enclosed or semi-enclosed protective devices and automatic chip removal devices.
When choosing CNC lathes and turning centers, the above principles should be considered comprehensively.
Although the processing flexibility of CNC lathes is superior to that of ordinary lathes, there is still a certain gap between the production efficiency of a certain kind of parts and ordinary lathes. Therefore, improving the efficiency of CNC lathes has become the key, and the reasonable use of programming skills to compile high-efficiency machining programs often has unexpected effects on improving the efficiency of machine tools.
1. Flexible setting of reference points
BIEJING-FANUC Power Mate O CNC lathe has two axes, namely spindle Z and tool axis X. The center of the bar is the origin of the coordinate system. When each tool approaches the bar, the coordinate value decreases, which is called feed; otherwise, the coordinate value increases, which is called retract. When retreating to the position when the tool started, the tool stops. This position is called the reference point. The reference point is a very important concept in programming. Every time an automatic cycle is executed, the tool must return to this position to prepare for the next cycle. Therefore, before executing the program, the actual positions of the tool and spindle must be adjusted to be consistent with the coordinate values. However, the actual position of the reference point is not fixed. The programmer can adjust the position of the reference point according to the diameter of the part, the type and quantity of the tool used, and shorten the idle stroke of the tool. Thereby improving efficiency.
2. Turn zero into a whole method
In low-voltage electrical appliances, there are a large number of short-pin shaft parts whose length-to-diameter ratio is about 2 to 3, and the diameter is mostly below 3mm. Due to the small geometric size of the parts, it is difficult to clamp on ordinary instrument lathes, and the quality cannot be guaranteed. If you program according to the conventional method, only one part is processed in each cycle. Due to the short axial dimension, the machine tool spindle slide block frequently reciprocates in the bed guide rail part, and the spring chuck clamping mechanism moves frequently. After working for a long time, it will cause local excessive wear of the machine tool rails, affect the machining accuracy of the machine tool, and even cause the machine tool to be scrapped. Frequent actions of the clamping mechanism of the spring chuck will cause damage to the control electronics. To solve the above problems, it is necessary to increase the feed length of the spindle and the action interval of the spring chuck clamping mechanism without reducing productivity. From this, it is conceived whether it is possible to process several parts in one machining cycle, the feed length of the spindle is several times the length of a single part, and it can even reach the maximum travel distance of the spindle, and the action time interval of the spring chuck clamping mechanism is correspondingly extended. Several times the original. More importantly, the original auxiliary time of a single part is divided among several parts, and the auxiliary time of each part is greatly shortened, thereby improving production efficiency. In order to realize this idea, the concept of the main program and subprograms in computer-to-computer programming, if the command fields related to the geometric dimensions of the parts are placed in a subprogram, the command fields related to machine tool control and the command fields for cutting off parts Put it in the main program. Each time a part is processed, the main program calls the subprogram once by calling the subprogram command. After the processing is completed, it jumps back to the main program. Calling several subroutines when several parts need to be processed is very helpful to increase or decrease the number of parts processed in each cycle. The processing program compiled in this way is also relatively simple and clear, which is easy to modify and maintain. It is worth noting that since the parameters of the subroutine remain unchanged every time it is called, and the coordinates of the spindle are changing all the time, in order to adapt to the main program, relative programming statements must be used in the subroutine.
3. Reduce the empty stroke of the tool
In the BIEJING-FANUC Power Mate O CNC lathe, the movement of the tool is driven by a stepper motor. Although there is a fast point positioning command G00 in the program command, it is still inefficient compared with the feed mode of the ordinary lathe high. Therefore, in order to improve the efficiency of the machine tool, the operating efficiency of the tool must be improved. The idle travel of the tool refers to the distance traveled by the tool when it approaches the workpiece and returns to the reference point after cutting. As long as the idle stroke of the tool is reduced, the operating efficiency of the tool can be improved. (For point-controlled CNC lathes, only high positioning accuracy is required, and the positioning process can be as fast as possible, while the movement path of the tool relative to the workpiece is irrelevant.) In terms of machine tool adjustment, the initial position of the tool should be arranged as much as possible. It may be close to the bar. In terms of program, according to the structure of the part, use as few tools as possible to process the parts so that the tools are dispersed as much as possible during installation, and they will not interfere with each other when they are very close to the bar. On the other hand, due to the actual initial The position has changed from the original position. The reference point position of the tool must be modified in the program to make it consistent with the actual situation. At the same time, with the fast point positioning command, the empty stroke of the tool can be controlled within the minimum range. Thereby improving the machining efficiency of the machine tool.
4. Optimize parameters, balance tool load and reduce tool wear
Since entering the 21st century, with the continuous development of CNC technology and the expansion of application fields, it has played an increasingly important role in the development of some important industries (IT, automobiles, light industry, medical, etc.) of the national economy and people’s livelihood, because these industries The digitization of required equipment has become a major trend of modern development. In general, CNC lathes present the following three development trends:
High speed and high precision
High speed and precision are the eternal goals of machine tool development. With the rapid development of science and technology, the renewal of mechanical and electrical products has accelerated, and the requirements for precision and surface quality of parts processing have become higher and higher. In order to meet the needs of this complex and changeable market, the current machine tools are developing in the direction of high-speed cutting, dry cutting and quasi-dry cutting, and the machining accuracy is constantly improving. On the other hand, the successful application of electric spindles and linear motors, ceramic ball bearings, high-precision large-lead hollow internal cooling, low-temperature high-speed ball screw pairs with strong cooling of ball nuts, and linear guide pairs with ball cages, and other machine tool functional components The market launch also created conditions for the high-speed and precise development of machine tools.
The CNC lathe adopts an electric spindle, which eliminates belts, pulleys and gears, greatly reduces the moment of inertia of the main drive, improves the dynamic response speed and working accuracy of the spindle, and completely solves the problem of belt and pulley transmission when the spindle is running at high speed. Vibration and noise issues. The electric spindle structure can make the spindle speed reach more than 10000r/min.
The linear motor has high driving speed, good acceleration and deceleration characteristics, superior response characteristics and following accuracy. The linear motor is used as the servo drive, eliminating the intermediate transmission link of the ball screw, eliminating the transmission gap (including backlash), the movement inertia is small, the system rigidity is good, and it can be accurately positioned at high speed, thus greatly improving Servo accuracy.
The linear rolling guide pair has zero clearance and very small rolling friction, low wear, negligible heat generation, very good thermal stability, and improves the positioning accuracy and repeat positioning accuracy throughout the process. Through the application of linear motor and linear rolling guide pair, the rapid movement speed of the machine tool can be increased from 10-20m/mim to 60-80m/min, up to 120m/min.
The reliability of CNC machine tools is a key indicator of the product quality of CNC machine tools. Whether the CNC machine tool can play its high performance, high precision and high efficiency, and obtain good benefits, the key depends on its reliability.
CNC lathe design CAD, structural design modularization
With the popularization of computer applications and the development of software technology, CAD technology has been extensively developed. CAD can not only replace the manual completion of tedious drawing work, but more importantly, it can carry out design plan selection and analysis, calculation, prediction and optimization of the static and dynamic characteristics of the large whole machine, and can carry out dynamic simulation and simulation of the working parts of the whole machine. . On the basis of modularization, the three-dimensional geometric model and lifelike colors of the product can be seen in the design stage. The use of CAD can also greatly improve work efficiency and increase the first-time success rate of design, thereby shortening the trial production cycle, reducing design costs, and improving market competitiveness.