Progress in the flexibility of modular machine too

The progress of modular machine tool flexibility

over the past decade, the automotive industry, as an important user of modular machine tools, in order to meet the personalized needs of people by finally displaying it in the measurement interface in a graphical way, the variety of automotive variants is increasing day by day, and it has become one of the characteristics of automotive market competition to compete in multiple varieties, which makes the modular machine tool manufacturing industry face the challenge of variant and multi variety production. In order to adapt to multi variety production, the traditional rigid modular machine tools and automatic lines that process a single variety must improve their flexibility. In the 1970s, the reliability of CNC system has been greatly improved, so by the late 1970s and early 1980s, companies such as ALFING, H ü ller Hille and ex-cell-o have successively developed CNC machining modules and flexible automatic lines (FTL), and since then, CNC modular machines and flexible automatic lines have increased year by year. From 1988 to 1992, the numerical control rate of the output of modular machine tools and automatic lines (including some other forms of special machine tools) in Japan has reached 32% - 39%, and the numerical control rate of output value has reached 35% - 51%; The numerical control rate of the output of German modular machine tools and automatic lines is 18% - 62%, and the numerical control rate of the output value is 45% - 66% (Table 2). These figures show that the CNC development of modular machine tools has been very rapid in the past decade. It should be pointed out that since the 1990s, the competition in the automotive market has become more intense, the service life of products in the market has been further shortened, the development cycle of new models has been shortened day by day (at present, it is generally 35 months), and the variety of automobiles has been increasing. Therefore, the demand for flexible automation technology and equipment in the automotive industry is increasing. For example, Toyota Motor Corporation of Japan aims to achieve 100% penetration of flexible processing systems in its subordinate factories by the end of this century. Obviously, it is more and more important to further improve the flexibility of modular machine tools and their automatic lines while maintaining their high production efficiency

Table 2 output and output value of Japanese and German CNC modular machine tools and CNC automatic lines (1988 ~ 1992), output year of Japanese modular machine tools and automatic lines 2954.91106.21590.11193.1 among them: CNC modular machine tool and CNC automatic line 7335.0539.9767.6607.2 numerical control rate (%) 32.331.936.939.038.235.135.148.848.350.9 German modular machine tools and automatic lines 2429.8712.2746.7896.9 among them: CNC modular machine tool and CNC automatic line 0196.0378.3490.6590.5 numerical control rate (%) 62.117.822.029.042.553.545.653.165.765.8 excerpted from 1993 ~ 1994economichandbookofmachinetoolindustry amt

1 Conveyor 2 Console 3 Hydraulic station 4 Material preparation station 5 Clamping station 6 Gantry empty frame robot 7 Cleaning station C three coordinate machining module 9 Conveyor belt 10 Turret multi axis machining module two coordinate milling module 12 Rail transport trolley 13 Storage station 14 The flexibility of manual clamping station

modular machine tool is mainly achieved by using numerical control technology. The important premise of developing flexible modular machine tools and flexible automatic lines is to develop NC machining modules, and machining center technology with a long history of development provides mature experience for the development of NC machining modules. Flexible modular machine tools and flexible automatic lines composed of NC machining modules can realize automatic tool change, automatic replacement of multiple axle boxes, and change machining stroke, working cycle, cutting parameters and machining position by applying and changing NC programs, so as to adapt to the machining of variant varieties. According to the number of NC coordinates (axes) of flexible modular machine tools and flexible automatic lines, there are mainly single coordinate (z), double coordinate (x-z, Y-Z, z-u, z-b, etc.) and three coordinate (X-Y-Z) processing modules; According to the number of spindles, there are single axis and multi axis processing modules, as well as single axis and multi axis composite processing modules

the single coordinate machining module is composed of CNC sliding table and spindle components (or multi axle box, including replaceable multi axle box). The two coordinate machining module is composed of CNC cross slide and spindle components, such as CNC two coordinate milling module. The column mobile CNC three coordinate machining module (Figure 6), whose tool can move in three coordinates, can be equipped with tool magazine, tool changing manipulator and required tools according to the variety of workpiece and machining task, and has high flexibility. This processing module is one of the most important modules for flexible automatic line to realize multi variety processing

the column mobile CNC three-axis machining module can use the linkage of x-axis and y-axis to realize the peripheral milling process, especially when milling workpieces with poor rigidity such as gearbox, the milling cutter with smaller diameter can be used to realize high-speed (cutting speed up to 2500m/min) peripheral milling, so as to reduce the cutting force and workpiece deformation during processing. This is much better than using the two coordinate milling module to mill with a large diameter milling cutter. Multi axis machining module is another important module, which is mainly used for flexible modular machine tools and flexible automatic lines for machining box and disk workpieces. This kind of module has many different structural forms, but it can be basically divided into automatic box changing multi axis processing module, turret multi axis processing module and rotary workbench multi axis processing module. Since the automatic box changing module can store more multi axle boxes in the specially set multi axle box library, it can be used to process more different kinds of workpieces. For turret type and rotary workbench multi axis processing modules, due to the limited number of multi axle boxes allowed on the turret head and rotary workbench (generally 4 ~ 6), this processing module can only realize the processing of a limited variety

using CNC three-axis machining module and turret multi axis machining module on the automatic line can not only realize the processing of different types of workpieces, but also realize multiple machining processes (rough boring, semi fine boring and fine boring; drilling, reaming and tapping) through its automatic tool change or box change on the same machining station within the beat time of the automatic line (if the beat time allows), Thus, the number of machining jobs of the automatic line is reduced and the length of the automatic line is shortened

the single axis and multi axis composite machining module is a three-axis NC machining module, which can realize single axis machining or multi axis machining by automatically changing the tool or automatically changing the multi axle box. It is worth mentioning that the cncmach modular system launched by the German Honsberg company in the mid-1980s is a very distinctive modular system. The system fully applies the principle of modular structure. On the CNC three coordinate module as the basic module of the system, by adding and subtracting various functional modules, it can be assembled into processing modules with different coordinates or without process use. Specifically, from the perspective of coordinates, in addition to three coordinates, it can also form two coordinate and single coordinate processing modules; From the perspective of tool magazine, tool magazine and multi axle box magazine can be installed, which can realize the automatic replacement of tools or multi axle boxes separately, and can also realize the replacement of tools and multi axle boxes in turn

the NC machining modules used in this line include four two coordinate NC milling modules, six NC turret multi axis machining modules and six NC three coordinate machining modules. Auxiliary stations include cleaning stations and clamping stations that use robot 1 to detect parameters. In fact, you don't know how to operate. Since the processing modules that make up the automatic line are all CNC, when the processing of one workpiece is changed to the processing of another workpiece, it is only necessary to change the CNC program without mechanical adjustment and refitting

4 machining accuracy is improving day by day Table 3 accuracy of key parts of car engine workpiece name item value flatness of top and bottom surface of cylinder block 0.02mm/1000mm cylinder hole aperture accuracy IT6 coaxiality of main shaft hole f0.01mm cylinder block stop depth 0.01 ~ 0.02mm coaxiality of cylinder head intake and exhaust valve seat and guide hole f0.02mm guide hole aperture accuracy IT6 cylinder block and cylinder head and other box parts process positioning pin aperture accuracy it5 hole spacing accuracy +0.01mm transmission shaft hole of transmission box Hole spacing accuracy +0.02mm hole diameter accuracy IT6 connecting rod big and small head hole diameter accuracy IT6 (big head hole) it5 (small head hole) hole spacing accuracy +0.01mm bolt positioning hole diameter accuracy IT6 hole spacing accuracy +0.03mm

1 Boring bar 2 Slide plate for finishing cylinder hole seam 3 Hollow taper shank (HSK) 4 Cutter head equipped with three cutting edges and three diamond guide bars 5 Precision boring tool for pull rod cylinder hole for turning stop

1 Automatic loading and unloading system 2 Rotary worktable modular machine tools for machining datum and locating pin holes 3 ~ 6, 8 ~ 10, 13 ~ 17, 21 Flexible automatic line for machining 7 Leak tester 11 Washing machine 12 Automatic assembly machine for conduit and valve seat 18 Deburring machine 19 Cleaning machine 20 The integrated production system of camshaft bearing cap automatic assembly machine cylinder head

especially since the mid-1980s, in order to enhance the competitiveness of its cars, the automobile manufacturing industry has continuously tightened the manufacturing tolerances of its key engine parts, and improved the quality of its products through computer-aided measurement and analysis methods, as well as through equipment capacity inspection. At present, when checking and accepting modular machine tools and automatic lines, it is generally required that the process capacity coefficient of the equipment should be greater than 1.33, and some even require that the process capacity coefficient should be greater than 1.67, so as to ensure stable machining accuracy. It should be pointed out that using CP ≥ 1.33 to accept the equipment actually tightens the manufacturing tolerance of the workpiece, that is, the actual machining tolerance of the workpiece is only 1/3 ~ 1/2 of the given tolerance of the workpiece, which undoubtedly puts forward higher requirements for modular machine tools and automatic lines. In order to meet the high requirements of users for the machining accuracy of workpieces, modular machine tool manufacturers, in addition to further improving the accuracy of spindle components, boring bars, fixtures (including boring dies), adopting new special tools, optimizing the cutting process, adopting tool size measurement control system and controlling the thermal deformation of machine tools and workpieces, currently, The application of hollow tool taper shank (HSK) and process statistical quality control (SPC) has become a new important technical means for automatic line to improve and monitor machining accuracy

hollow tool taper shank is a novel tool that uses radial (conical) and axial (end) two-way positioning. Its advantages are high bending stiffness, torsional stiffness and high repetition accuracy. Using the boring tool with hollow taper handle on the machine tool, it7/it6 precision holes can be machined with the preset tool. The application example of hollow tool taper handle on cylinder bore precision boring tool is shown in

spc is a method based on process capability to monitor the processing quality of the workpiece from the surface. The target travel limit switch can be unloaded automatically after the end of the experiment. Before it plays the role of limit shutdown, this quality assurance system is increasingly used to continuously monitor the processing quality in the whole production process on the automatic line. Table 4 shows the actual machining tolerances of cylinder head valve guide bottom hole and valve seat bottom hole when SPC monitoring is adopted. Table 4 actual machining tolerance of cylinder head valve guide bottom hole and valve seat bottom hole when SPC monitoring is adopted (mm) hole diameter tolerance of machining part actual machining tolerance under SPC monitoring (pro