Numerical control system and its application in surface grinder

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In modern industrial production, the production of small and medium-sized parts accounts for an increasing proportion of the number of products. The complexity and accuracy requirements of parts are rapidly increasing.

I. Introduction

In modern industrial production, the production of small and medium-sized parts accounts for an increasing proportion of the number of products. The complexity and accuracy requirements of parts are rapidly increasing. Traditional ordinary machine tools have become more and more difficult to meet the requirements of modern production, while CNC machine tools It has the characteristics of high precision, high efficiency, multiple functions in one machine, and can complete complex surface processing, especially the rapid development of computer technology and widely used in numerical control systems. The main functions of numerical control devices are almost all realized by software, and hardware can almost Versatile, making it more flexible in processing and more powerful in functions.

The competition in the manufacturing industry has evolved from the early competition to reduce labor costs and product costs, and to improve the overall efficiency and quality of the enterprise, to the competition to fully meet customer requirements and actively develop new products. It will face the knowledge-technology-product competition. The renewal cycle is getting shorter and shorter, the product batch is getting smaller and smaller, and the requirements for quality and performance are higher. At the same time, the society's awareness of environmental protection and green manufacturing is constantly strengthening. Therefore, agile and advanced manufacturing technology will become the main means for enterprises to win competition and survive and develop. The combination of computer information technology and manufacturing automation technology is getting closer and closer. As an important basis for automated flexible production, CNC machine tools will account for more and more of the production machine tools.

2. The status quo of CNC flat grinding and main CNC systems

Compared with lathes, milling machines, etc., surface grinders adopt numerical control systems later because of its special requirements for numerical control systems. In the past ten years, with the help of CNC technology, continuous dressing of grinding wheels, automatic compensation, automatic exchange of grinding wheels, multiple worktables, automatic transmission and clamping of workpieces have been realized, and CNC technology has gradually become popular on surface grinders. In recent years, large-scale machine tool exhibitions in Hannover, Tokyo, Chicago, and domestic, CNC grinders have accounted for the majority of the entire grinder exhibits. Famous grinder manufacturers such as German BLOHM and ELB no longer produce ordinary grinders. Ben, Nikko and other companies also produce full-function CNC flat grinders in batches. While developing high-end CNC flat grinders, they are actively developing medium and low-grade CNC flat grinders.

In the past few years, the BRILLIANT series two-coordinate CNC forming grinder produced by German ELB company has vertical and horizontal CNC axes and hydraulic control in the longitudinal direction. The grinding wheel dressing adopts diamond rollers installed on the worktable, which has a wide range of applications; SUPER-BRILLIANT series It is a three-coordinate CNC plane and profile grinder. The bed is made of natural granite and has extremely high geometric accuracy. The guide rail is linear rolling guide, and the mechanical drive has no backlash, so as to ensure that the workpiece has a better surface finish; BRILLIANT-FUTURE is the above two A series of improved products, the bed is made of artificial granite, the longitudinal use of static pressure guide, toothed belt transmission, the vertical and horizontal guides are preloaded linear rolling guides, ball screw transmission, three-axis CNC control AC servo motor, 0.5 The measurement resolution of μm. At the same time, ELB company has developed grinding machine products with the latest contemporary technology, namely the CAM-MASTER series flexible grinding processing unit based on mechatronics and computer technology, the CAD-MASTER series and the COMPACT-MASTER series grinding processing center, with the most control axes. It can reach 24 axes. In addition, due to the comprehensive implementation of modular design, the manufacturing cycle of special grinders is shortened. ELB has also developed a variety of high-efficiency special grinders, such as SFVG100/2 special grinders, which have tiltable grinding heads, continuous dressing, and slow feed. , The oblique cut into the grinding function, with eleven CNC control axes, like the same grinding machining center. British JONES&SHIPMAN company and American AB company developed A-B8600 numerical control system for FORMAT5 numerical control flat grinding. The hydraulic valve is controlled by CNC, which drives the longitudinal adjustable speed movement, the horizontal and the grinding head feed with the ball screw pair, and the DC servo motor. Drive, intermittent grinding wheel dressing, CRT graphic simulation display. At the same time, it can also be equipped with other types of CNC systems to meet the requirements of different users.

At present, with the continuous improvement of semiconductor integration, the newly introduced system is getting smaller and smaller in appearance, more and more compact in structure, and in functions, remote communication, remote diagnosis, multi-machine networking, etc. are added; the operation interface is closer to the WINDOWS system. , Increase the mouse, remote control and other operating parts. FANUC company this year mainly launched 18I, 16I, 20I, 21I systems, SIEMENS 840D, 810D, 802D are all compact systems. There are also some manufacturers such as the PA8000NT series CNC controller developed by Taiwan Precision Machinery Research and Development Center, which uses the WINDOWS NC operating system and the NT real-time multiplexing processing core. The processing speed of a single program can reach 2000 blocks/sec. The number of reading processing can reach 1000, with AART (pre-adaptation adjustment technology) and parameter optimization learning function, which can make the following error approach zero. The software processing path filter can reduce the acceleration caused by excessive changes in the cutting process. The generated mechanical resonance can improve the surface roughness; it is flexible to use servo, with +, -10V analog servo interface, and provides international standard SERCOS digital servo communication interface; PLC program design has ladder diagram, structure statement, function block, instruction Five grammars such as code and flow chart are convenient for design, communication and maintenance; with computer remote communication, instant remote maintenance functions; control axis and spindle can be extended to 64 axes at most, I/O points can be extended to 792/528 points, using Pentium processor, high-speed PLC processing speed up to 25K.

In addition to the famous SIEMENS, FANUC and other CNC system companies that have developed and produced many systems suitable for surface or profile grinding, some flat grinding manufacturers themselves have also actively developed CNC systems suitable for their grinding machines. There are:

The SINUMERIK 840D system of Siemens, which has more than 20 servo axes, coordinate continuous stroke control, manual data input or input through an external computer, remote diagnosis, can change the stroke as the diameter of the grinding wheel decreases, and the amount of grinding wheel dressing is automatically compensated. Ball screw clearance error compensation, etc.

The Siemens 3G system is specially developed for grinding processing. It is equipped with an operation prompt device for man-machine dialogue. When the axis is tilted, linear and arc interpolation can also be performed. The operation cycle that often occurs in grinding, such as Spindle swing, use external signal to interrupt execution program, grinding wheel cut-in, grinding wheel dressing and other special preparation functions, and compile canned cycle programs. It can not only use an external measuring device (switch signal), but also directly control the device and compare the final size when a suitable measuring head is connected.

The 8400CNC and 8600CNC series produced by the American ALLEY-BRANDLY company are suitable for lathes, milling machines and grinders. The 8400CNC can control up to 6 servo axes, any 2 axes can be used for circular interpolation, and any 3 axes can be used for helical interpolation. , 6-axis linear interpolation. The 8600CNC series can control up to 17 coordinates, including 8 participating interpolation axes, 8 bit control axes and 1 spindle. It has functions such as graphic display, extended branch program, display processing time, high-speed program verification, and tool life monitoring.

Japan FANUC company developed the OG high-speed high-performance CNC system. Among them, O-GSG is suitable for surface grinders. There are four different grinding methods according to the different shapes of the parts to be ground. It has the function of controlling the angle of the grinding wheel axis, such as rough grinding and rough grinding. A complete set of grinding cycles for grinding, fine grinding and non-spark grinding, position compensation function for grinding wheel after rolling and dressing, control function of the dresser relative to the normal direction of the dressing wheel, compensation for the radius of the outer edge of the dressing wheel, and the shape of the grinding wheel Display function and grinding parameter display, etc. The minimum setting unit of the system is 0.1μm, which is a "compact" CNC system, and the price is relatively low.

There is also the UNICON system jointly developed by the German ELB company and the university. The surface and profile grinding CNC system developed by Japan’s Okuma Iron Works OSP5000G-G, OSP30-NF, etc., its OSP5000G-G can control up to 9 coordinates, of which 6 coordinates can be linked, with 12-inch color display, man-machine Dialogue programming, automatic determination of cutting coefficient, can be input by floppy disk, incorporated into the FMS system, the minimum pulse equivalent, movement equivalent and detection equivalent are all 0.1μm, and the inductive synchronizer full-closed loop method is also used for flat grinding.

Although some flat grinding factories use the system of the CNC OEM, they develop their own software, which is more suitable for surface and profile grinding. For example, the German JUNG company uses Siemens SINUMERIK 810 as the basis and uses the company’s special software, using JUNG KONTUR The programming language performs shaping and dressing of the grinding wheel, and has graphics auxiliary operation functions. Japan's Okamoto company developed the OPL language for grinding processing on the FANUC company's CNC system hardware, and so on.

Today's linear motors, dynamic balancing and other technologies and processes are increasingly developed, which have greatly improved the ergonomics of machine tools. The development and utilization of CNC systems by suitable measurement technology applications has enhanced the electrical automatic control functions of machine tools.