Precision control has an important effect on the quality of CNC lathes in the production of CNC lathes. Machining accuracy depends on mechanical accuracy, programming accuracy, servo accuracy and complement accuracy. In order to improve the machining accuracy of CNC lathe, through CAD design and computer simulation technology, the machining accuracy of CNC lathe can be effectively improved in the design stage. Strengthen the maintenance of the machine in use, can effectively ensure the high precision state of CNC lathe.
1, CNC lathe processing accuracy analysis
At present, the classification of CNC lathes is mainly set accuracy, position accuracy and machining accuracy. The material stiffness of different brands of CNC lathes is different (the quality of CNC lathe equipment), the temperature at work will have a variety of influences on the accuracy of CNC lathe processing. CNC lathe geometric accuracy continues to subdivide can also be divided into spindle geometric accuracy and linear motion accuracy.
In the nc lathe processing operation, the relative position between the spindle and the rotating shaft remains relatively fixed, in actual production and theoretical knowledge is not exactly the same, the relative space position between the two axes is not necessarily relatively fixed. This is because the bearing elements that make up the spindle may have different degrees of error in the production plant that makes the lathe equipment, and will be affected by temperature, working intensity, lubrication and other conditions in the process of use. Due to the bearing accuracy of the spindle, the quality of manual assembly of the spindle box is different, the runout caused by mechanical vibration of the spindle and rotating parts in the process of processing, the roundness of the bearing journal of the central shaft is unstable in the manufacturing process, the concentricity of the front and back is certain error, and the thermal deformation may occur in the working process of the spindle. All these factors affect the geometric accuracy of CNC lathe spindle.
In addition to the geometric error of the spindle in CNC lathe processing, the track may also affect the position accuracy of the machine due to friction and the inertia matching problem of the servo motor used in CNC lathe processing. CNC lathe processing some need uninterrupted work, such as cylinder pump, motor, hydraulic machine, etc., need a long time continuous work (even 24 hours). In the process of work, friction leads to specific internal parts, due to the thermal expansion deformation of processing heat, resulting in the actual production size of parts and design of the size of the reservation deviation, due to the role of internal heat led to CNC lathe equipment components asymmetry caused by the production of parts deformation, Therefore, the thermal deformation of CNC lathe equipment components will have a key impact on the position accuracy of the machine.
CNC numerical control lathe machining precision and the overall geometric accuracy of CNC lathe processing in addition to closely related and location accuracy, and numerical control lathe processing and the transmission system fault, check the friction fault compensation system, machine structure, cutting tool position error and so on, also with the CNC numerical control lathe processing editing program is correct, production technology is reasonable. Therefore, in the actual production, in order to improve the machining accuracy of NC lathe, we must improve the geometric accuracy and position accuracy of NC lathe processing.
2, check the accuracy of CNC lathe processing
CNC lathes and all other electrical and mechanical equipment, after a period of use, will face aging electronic parts, structural parts rust, mechanical parts wear and other problems. Therefore, in order to make the CNC lathe processing to maintain a better state, it is necessary to regularly maintain the CNC lathe, test and calibrate the accuracy of CNC lathe processing.
(1) Geometric accuracy detection
CNC lathe processing geometric accuracy inspection of the main project, used for linear motion axis straightness inspection project tools are flat ruler and dial table, these two tools usually test vertical to the other two axes of the linear deviation of the moving parts. For example, in a most common vertical CNC machining center, the test of set accuracy mainly includes the flatness of CNC lathe processing and the verticality of the motion axis moving in all directions. The runout of the main shaft, the main shaft, the axis line of the rotating shaft and the vertical direction of the mechanical table. The parallelism of the workbench when the x and Y axes of the machine move; Parallelism of t-shaped side slot of worktable when moving in x coordinate direction; When the coordinate direction of z axis moves, the straightness of the main axis and the parallelism of the main axis, and the runout of the main axis.
(2) Detection of position accuracy
The position accuracy required by CNC lathes can be divided into positioning accuracy, reverse deviation accuracy and repeated positioning accuracy. The accuracy of positioning is mainly affected by the working table or motion structure processed by CNC lathe. The actual motion position in production is highly consistent with the position of the program code. The inconsistency difference is the positioning accuracy error, and the servo system, detection system, feed system error and the geometric error of the machine tool movement structure are the important factors that directly affect the precision error of the parts size in production and processing.
3. Measures to improve the machining accuracy of CNC lathe
(1) Improve the design level
At present, we commonly used CNC lathe to domestic CNC lathe processing, CNC lathe production enterprises basically have part of the independent research and development ability, can design, manufacture, improve the main components of the product, the functional parts of the CNC lathe need to buy. The local force of the closed eye machine tool is too large and normal, resulting in large deformation and affecting the machining accuracy.
Most of the machining accuracy of machine tools is mainly affected by the wear-resisting degree and temperature rise of the spindle, so the temperature characteristics can be optimized according to the production and processing of parts, and the machining accuracy can be effectively maintained. The design of general machine tool spindle system is to install the core structural parts that affect the machining accuracy on the mounting surface perpendicular to the machine base, and to install additional structural parts symmetrically on both sides of the spindle box, so as to effectively improve the machining accuracy.
(2) improve the geometric accuracy of CNC lathe processing
The geometric precision of NUMERICAL control lathe is the core condition of the machining precision of numerical control lathe. Therefore, in the design of machinery manufacturing enterprises, the working precision of the machine must be set reasonably and the processing load should be selected appropriately. When CNC lathe processes parts, the friction between the spindle neck and the bearing will lead to temperature rise, and the space position of the box hole on the spindle box will lead to rolling deformation of the bearing, seriously affecting the bearing rotation accuracy. Therefore, the optional clearance of spindle bearing is strictly controlled. CNC lathes in the processing of a part required time is high load state operation, general machinery manufacturers use inlaid steel sliding guide auxiliary structure, improve the stiffness and accuracy of the machine. This structure enables nc lathes to have extremely high geometric accuracy.
(3) improve the comprehensive machining accuracy
From design to manufacturing, assembly, the use of programming instructions, CNC lathe machining precision control is a comprehensive system, rather than by controlling a single or specific numerical value to obtain high machining accuracy. In the manufacturing environment, it is necessary to fully consider the factors affecting the mechanical accuracy in the manufacturing process to eliminate the geometric accuracy variation of each structural part caused by casting and mechanical processing. Then set the compensation value for the NC system of nc lathe to effectively improve the machining accuracy.
4, the conclusion
Although the CNC lathes used in Mainland China have higher processing accuracy than traditional mechanical lathes, they are quite different from the advanced CNC equipment in the world. With the existing conditions in China, in order to improve the processing quality of CNC lathe processing, maintain higher processing accuracy, we must further improve the production technology, and constantly improve the design and production capacity. We need to grope in the actual production in the future, improve the process, in a large number of technical personnel day after day precious production experience to make bold innovation, to achieve capacity optimization. We still have a long way to go.
