1、 Characteristics of CNC machine tools in processing
1. High accuracy
(1) The structure of CNC machine tool has high rigidity and thermal stability, and measures to reduce errors have been taken. The error can also be compensated by the numerical control device, so the numerical control machine tool has high processing accuracy.
(2) The transmission system of the CNC machine tool adopts the ball screw without clearance, rolling guide rail, gear mechanism with zero clearance, etc., which greatly improves the transmission rigidity, transmission accuracy and repetition accuracy of the machine tool. The advanced CNC machine tool adopts linear motor technology, so that the mechanical transmission error of the machine tool is zero.
(3) The error compensation function of the CNC system eliminates the system error.
(4) CNC machine tools are automatic processing, eliminate human error, improve the uniformity of the processing size of the same batch of parts, and stabilize the processing quality. One installation can carry out continuous processing of multiple processes, reducing the installation error.
2. Be able to process parts with complex shapes
The CNC machine tool with more than two axes linkage can process the rotating body, cam and various parts with complex spatial surfaces whose generatrix is curve, and can complete the processing that is difficult to be completed by ordinary machine tools. For example, marine propeller is a complex part of space curved body, which can be processed only by using end milling cutter and five-axis linkage horizontal CNC machine tool.
3. High productivity
(1) Save auxiliary time
CNC machine tools are equipped with automatic tool change mechanisms such as indexable tool rest and tool magazine. The manipulator can automatically load and unload tools and workpieces, greatly saving auxiliary time. No inspection is required in the production process, saving inspection time. When the processing parts are changed, in addition to reloading the workpiece and changing the tool, only the program needs to be changed, which saves the preparation and adjustment time. Compared with ordinary machine tools, the productivity of CNC machine tools can be increased by 2-3 times, and the productivity of machining centers can be increased by 10 to dozens of times.
(2) Increase feed speed
CNC machine tools can effectively save the time of movement, shorten the time of empty travel by rapid movement, and have a large range of feed rate. It can effectively select reasonable cutting parameters.
(3) Adopt high-speed cutting
Small diameter tools, small cutting depth, small cutting width, and fast multiple cutting paths are used to improve cutting efficiency in NC machining.
The cutting force of high-speed machining is greatly reduced, and the required spindle torque is correspondingly reduced.
The deformation of the workpiece is also small. High speed cutting not only improves productivity, but also helps to improve machining accuracy and reduce surface roughness.
2、 Adaptability and economic characteristics of CNC machine tools
1. Strong adaptability
CNC machine tools can adapt to different types, specifications and sizes of workpiece processing. When changing the processing parts, you only need to use the universal fixture to clamp the workpiece, change the tool, and change the processing program, and then you can immediately process. The computer numerical control system can flexibly increase or change the functions of the numerical control system by using the system control software, and can adapt to the needs of production development.
2. It is conducive to the development of a more advanced manufacturing system
CNC machine tool is the basic equipment of mechanical processing automation. Flexible machining unit (FMC), flexible manufacturing system (FMS) and computer integrated manufacturing system (CIMS) all take CNC machine tool as the main body. According to different processing requirements and different objects, one or more digital control machine tools, together with other auxiliary equipment (such as transportation trolley, robot, interchangeable workbench, three-dimensional warehouse, etc.), form an automatic production system. The CNC system has a communication interface, which is easy to communicate between computers and realize computer management and control of the production process.
3. Economy of CNC machine tools
The cost of CNC machine tool is higher than that of ordinary machine tool, and the processing cost is relatively high. Therefore, not all parts are suitable for processing on CNC machine tools. It has a certain range of processing applications. It is necessary to determine whether the product is suitable for processing with CNC machine tools according to its production type, structure size and complexity.
Universal machine tools are suitable for single piece and small batch production, and the processing structure is not too complex.
Special machine tools are suitable for processing large quantities of workpieces.
CNC machine tools are suitable for batch processing of complex workpieces.
3、 Characteristics of NC machine tools in management and use
CNC machine tools are expensive, and they are key products and key equipment in key processes of enterprises. Once the machine is shut down due to failure, its impact and loss will be great. As an electromechanical integration equipment, CNC machine tools have their own characteristics.
The technical level of management, operation, maintenance and programming personnel is relatively high. The use effect of CNC machine tools depends to a large extent on the technical level of users, the formulation of CNC processing technology and the correctness of NC programming. Therefore, the use technology of CNC machine tools is not a problem of general equipment use, but a technical application project of talents, management and equipment system. The users of CNC machine tools should have rich process knowledge and strong operation ability in the application of CNC technology, so as to ensure that the CNC machine tools have a high integrity rate and operating rate.
4、 Types of NC programming
NC programming is divided into manual programming and automatic programming.
1. Manual programming
(1) Determine the technological process, carry out technological analysis according to the part drawing, and determine the technological parameters such as the technological route, step sequence, cutting amount, etc. of the part processing. Determine the tools used and the number of tools.
(2) Calculate the machining path and size
(3) Compile program list and verify
(4) The contents of the input program list are input into the NC device through the input device.
(5) The calibration and trial cutting of the numerical control program start the numerical control device, make the numerical control machine tool idle, and check the correctness of the program motion path. Use wood or plastic products to replace the workpiece for trial cutting, and check the correctness of cutting amount.
(6) First piece test cutting
2. Automatic programming
The process of making NC machining program with the help of computer is called automatic programming.
For parts with complex geometry, manual programming is relatively heavy and prone to errors.
The programming and calculation of space surface parts is very complicated and manual work is not competent. In automatic programming, the data calculation of node coordinates, the generation of tool path, the programming and output of the program are automatically completed by the computer.