1. Research status of numerical control transformation at home and abroad.
Some developed countries such as Japan, the US and Europe attaches great importance to the modification of nc manufacturing enterprises to improve enterprise core competitiveness tried to transform ordinary machine tools into nc machine tools, and even some companies to develop common machine tool numerical control transformation into an industry, such as the German Schioess company, US equipment company in the United States, these companies are world famous ordinary numerical control machine tool company.
Under the limitation of manufacturing technology at that time, China's machinery manufacturing industry has about 80 percent of the equipment in the machinery manufacturing industry, and the degree of numerical control is very low.Due to the numerical control transformation technology is relatively backward, technology in the numerical control machine tool is mainly used in national defense military machine tool equipment, since the 1980 s is not a large number of proficient in numerical control machine tool technology experts for ordinary lathe numerical control transformation technology the development of a large number of fruitful research, have made significant achievements.
2. The necessity of nc transformation of ordinary machine tools.
2.1 the ordinary machine tools are deficient in the digital environment.
Restricted by technology, conventional machine tools in the machining precision, stability, reliability, quality, production efficiency, improve working conditions, production management modernization is far compared with nc machine tool.Ordinary machine tool technology is simple and simple, can only carry out single operation, but for more process parts, complex parts production requirements cannot be completed.
Processing time and auxiliary time affects efficiency, more ordinary machine tools machining precision is low, the low degree of automation, a lot of operating processes rely on workers, the labor intensity is high, the product quality consistency is poor, often can't ensure the quality of machining parts.
2.2 the advantages of the CNC transformation of ordinary machine tools.
Flexibility is good, when different ordinary numerical control machine tool machine tool in machining parts often need to make many fixture, mold and change, machining parts after the modification of the nc machine, the key depends on the program design, input, edit, often does not need to machine tool adjustment;The machining parts are of stable quality and good consistency. The same processing procedures and tools are used to process a batch of parts on a CNC machine tool. The machining conditions are exactly the same.Production efficiency is high, the nc machine tool compared with ordinary machine tool, and machining center knife library with components of the auxiliary time and can effectively reduce the processing time, CNC machine tools allow for a larger quantity cutting strong cutting, feed expanding.
In addition, with the tool library of machining center, it can be used for continuous processing of multiple processes on one machine tool, and the turnover time between processes is greatly reduced and the productivity is increased.
Machining accuracy of nc machine tools in general can reach 0.05 mm -- 0.1 mm, the average nc machine screw pitch error and reverse clearance of transmission chain of feed can be made of nc device march compensation, numerical control machine tool is implemented by digital signal form control the machining accuracy, machine tool for every pulse equivalent moving by the nc device outputs a pulse signal, therefore, the numerical control machine tool positioning accuracy is higher.
Use of modern production management, in the numerical control machine tool parts processing, can be on the fixture, tool used by standardization, and estimate the auxiliary time, processing time, the parts to modernize management.Nc machine tool compared with ordinary machine tools to improve the working conditions, adjust nc machine tools, processing before input and start the program, for parts for processing, CNC automatic continuous until parts processing.
3. Numerical control reform measures in digital environment.
3.1 fully understand the modified machine tool.
Nc machine tools are generally composed of measuring system, servo system and nc system.Whether the nc transformation of the ordinary machine tool is to be local or complete is to be determined by the transformation cost of the ordinary machine tool and the original parameter performance.Must first understand the existing in the process of numerical control transformation to transform the function of the machine tool, the precision of parameters, mechanical transmission, operation condition, and anticipate the performance of the modified conventional machine tools whether can meet the requirements, specific to clear the following items:
(1) determine the model of ordinary machine tools.
(2) the parameters and performance parameters of ordinary machine tools needed to be modified should be accurate.
(3) the number of control axes should be selected carefully because of the numerical control transformation of ordinary machine tools, because the number of axes directly determines which numerical control system to choose to match.
(4) before the CNC transformation of ordinary machine tools, it is necessary to know the core functional parts of the machine, such as gearbox and tool holder, so as to ensure that the CNC machine can produce and process complex parts.
(5) in order to ensure the accuracy of ordinary machine tool numerical control transformation after the expected requirements and function, the numerical control transformation of nc machine tools with parameter and mechanical performance by structure parameters estimate to have enough.
(6) it is necessary to understand some auxiliary safety performance parameters of the machine tool before the CNC transformation of ordinary machine tools, so as to ensure the safety of operation personnel after the CNC transformation.
(7) to consider in the process of ordinary machine tool numerical control transformation of the existing electric control system can meet the requirements of reformed nc machine tools, if can't meet the requirements, you must pass a programmable logic controller for modification.
3.2 numerical control system selection based on digital environment.
The key of nc transformation of common machine tool based on digital environment is the selection of nc system.Model selection according to the need to reform the machine parameters, performance parameters to choose the appropriate numerical control system matching, to ensure that after the modification according to the conventional machine tools in advance, the default JiHaoDe function requirement of parts processing, otherwise unable to reach function estimates.
Market have different function, different types of CNC system is numerous and complicated, so when choosing the numerical control system based on digital environment, should be considered before modification functions and characteristics of ordinary machine tool, numerical control transformation to achieve the accuracy requirement, function expected after modification cost and expected;In addition, special attention should be paid to the technical support provided by the manufacturer of the CNC system when selecting the CNC system.
Different CNC system on the need to reform the mechanical structure of the machine tool, drive device has different specific requirements, not all machines are able to do numerical control transformation, nor any to numerical control transformation machine matching with all different nc system, must choose the appropriate numerical control system to match, to achieve numerical control transformation.
3.3 design and transformation of mechanical structure based on digital environment.
Common machine tool nc transformation is key to the numerical control system selection, but in order to make the numerical control machine tools machining precision, function parameters, to get to the electrical supply system and machine safety operation procedures and requirements, the mechanical structure of nc machine tools in the process of transforming part had to redesign and rebuild.First, the design of mechanical structure based on digital environment.Must to force analysis of machine transmission shaft and other mechanical parts, to ensure that cutting CNC machine can perform a large amount of strong cutting, on the basis of analysis of the mechanical machine tool industry standards and national standards.
According to stress analysis and calculation results, to ensure that the numerical control machine tools machining precision, function parameters, to get to the electrical supply system and machine safety operation requirements needed for the main force of mechanical parts size and the size of the power supply device, numerical control transformation of machine tool in the mechanical structure design and modification, can be reference to successful cases, consult the relevant technical documents, to the scene of the reform successful business field research.
Will type CA6140 engine lathe numerical control innovation, throughout the design process must implement the following requirements: the main transmission system of lathe be retained, open loop transverse feed system consists of microcomputer control, two axes linkage;The tool holder adopts the automatic turning tool holder with the function of cutting thread.In X upward, the feed pulse yield is 0.005mm/pulse;At 3 -- 1000mm/min, the speed range is stepless, and the speed is set at any speed in X direction, 1000-3000mm /min.
Secondly, based on the digital environment, the mechanical structure transformation requirements.As far as possible, the size is unchanged or not changed when the mechanical component is modified, and the ideal mechanical transmission structure device is used to satisfy the maximum transmission ratio, so as to improve the efficiency of production and processing.The mechanical parts needed to be modified must meet certain accuracy requirements, such as surface roughness, geometric tolerances, hardness and strength, etc. to ensure smooth moving parts and reduce frictional resistance.Without the need to increase the power, the CNC machine can be used to produce more complicated parts.
The CA6140 ordinary lathe is transformed into an economical nc lathe, and the lateral feed mechanism is transformed into a numerical control tool holder by transforming the small drag plate and the manual tool holder.Ball screw nut is replaced by slide box, light rod feed box and ordinary screw rod;The manual mechanism of the adjustment operation remains unchanged, while the supporting structure is retained. The gear box body and stepping motor are installed in the back of the middle towing plate, and the gearbox adopts the first gear reduction.