| The writing performance of a ball pen quite depends on quality of its tip. However, because of the backward of our traditional manufacturing machine in ball pen industry, there are still some advanced ones imported from abroad. Of course, it has produced great impact to our ball pen industry and forced our engineers to research in this new field.By the development for decades, pen industry of China has become an industry with the capacity to manufacture various kinds of pens for home and abroad and the quantity of the pens for export has been increasing from year to year. Now China has grown into a big pen manufacturer and exporter. But there is a big gap in the type, quality, technology and equipment of pen compared with the modern country. In the thesis, the situation and development tendency of our country and abroad and the problems of our pen equipments are presented briefly. Besides, the superiority and orientation in the development of Chinese pen industry are also put forward.With the requirement for better writing function and better quality of pens, the structure of the pen tip has got much more complicate. In order to improve the pen machine efficiency and processing quality of pen's parts, many machines are imported in some pen factories. In the thesis the development and application, in ball pen industry, of multi-station small power unit machine are summarized. The characteristics of several types of the machine are compared. Based on all these work above mentioned, the technology index of multi-station machine developed in the project are brought forward; precision grade range IT3～IT4; surface roughness Ra=0.2～0.4μm; repeat position precision <0.04; 24 working stations at the top and bottom work synchronously, that means there are 48 working positions at most and only one mount of the part is needed for automatic processing from raw material to end product. Therefore, the accumulate error caused by more mounts is avoided.Structure parameters of the 24 multi-station small power unit machine are designed. The system is composed of: power system, power transfer system, control system, speed-adjust system and display system. The machine, with compact structure and high control precision, is a combination of automation and mechatrnicals.The rotor and its bearing, linked with small clearance restrict, makes up of the whole rotating system of unit power in ball pen production machine; its breakage and failure, first appear in the form of the failure of small clearance restrict, is caused directly by the unit vibration. Therefore, how to ensure good dynamic characteristics of rotating system is the thing worthy of note. Because of the variable factors, which have great influence on dynamic stability of the rotating system, and great error caused by the incomplete dynamic model with rotor destabilization, it is too difficult to do the nonlinear stability analysis. However, some effective trials on this aspect have been made in this project.The working speeds, close critical speeds, of the system must be avoided to ensure smooth running of the rotor from start to stop. The calculating model of the small power unit is built. The first and second critical speeds of the system are 2887.8r/min and 8255.7r/min respectively. The result shows that the working speed (4000~4500r/min) designed in the project is safe. The influences of shaft diameter, distance between bearings and support stiffness on critical speeds are also discussed, which can be adopted for adjusting working speeds and structure parameters.The effect of the friction moment of bearings on performance is researched. The forming mechanic and influence factors of the friction moment of ball bearing are analyzed. Suitable clearness and groove radius of ball bearings are obtained by experiment and calculation. The relationship between starting moment of ball bearing and various lubricants is analyzed. The measure for reducing the starting moment of ball bearing is put forward, it is the theory basis and reference for ball bearing design of small power unit system.The system is an unstable system when the 24-station ball pen tip production machine is running because of various interferences. It is too hard to describe the system by linear method, so the nonlinear formulation must be used. As one of the nonlinear and numerical analysis methods, the cell-mapping method is used here to analyze for the rotating small power unit system systematically and roundly, that's a new trial for the stability analysis of the actual rotating system of the small power unit, as well as providing a better theory for the practical design and manufacture. The research shows, whatever a nonlinear balanced bearing-rotor system or a nonlinear unbalanced one it is, its attenuation of destabilization movement relates to the track of the periodic movement on condition that there is a certain track of the shaft. The attenuation rate varies with different positions under destabilization in the system.With the increase of the running speed of the machine and the usage of new material and new structure, the shortage of the linear theory when solving the dynamic problems of rotor system, especially the small power unit, gradually become obvious. There are serious shock exciting sources, such as oil film force and sealing force, existed in rotor system, which resulting in many nonlinear problems, especially for the system with the faults of crack, base slack, rubbing and oil film oscillating. In many cases, there will be not only the amount errors but also the quality mistakes if nonlinear problems are simplified to the linear ones. Sometimes, serious faults occur mainly due to the reason that nonlinear factors are ignored when many small rotor systems are running. Therefore, the traditional rotor dynamics can't meet the needs of the modern design. The nonlinear theory must be adopted for better study of the complicated dynamic behaviors of the small power rotor system. The research based on nonlinear theory can not only avoid the solution limitation caused by the forced partition, which have to be done for parameter linearization, of nature vibration and forced vibration, but also put the forced vibration and other vibration exciting factors into mechanics model.In a 24-station small power unit system, there are several intercoupling faults, usually two or more faults concurrence in common condition. Therefore, the coupling mechanism has been mainly studied in this project. As above mentioned, the faults of the rotating system of the small power unit include the rubbing among the fixed and moving parts, rotor crack, oil film oscillating, slack between bearing seat and foundation, unhomocentric condition, combination of these coupling faults and so on. Coupling faults are more complicated than the single rotor faults and have influence each other. For example, the rotor system with shaft crack will cause rubbing in certain occasions, or the system with oil film oscillating will bring the rubbing, unbalance or unhomocentric faults, which will result in the rubbing among the fixed and moving parts and foundation slack. The nonlinear problems will be more obvious when the coupling faults occur in the rotor system. Because of the existence of inevitable nonlinear factors, it will be easier to study the mechanism of the coupling faults by the method of nonlinear dynamics and obtain the further nonlinear dynamic characteristics of the coupling faults system.Many theoretic analyses referring to the rotating machinery, such as the power unit system, are based on the data obtained from a great deal of observations and experiment data. However, it is still hard to make complete theoretic analysis of some problems and calculation related, because of fact the actual study objects, such as the stress condition of rotating machinery under dynamic load, dynamic characteristics of natural frequency, damping and vibration mode, confirmation of the fatigue life of the structure, are very complicated. In this case, the detection of the state parameter of the controlled object is absolutely necessary, especially in a loop control system. As is well known, there would be no automatic production without detection and data acquisition in the processing. In addition, control level depends on detection lever. Therefore, on-line detection and intelligent control of the multi-station power unit system are studied in this paper accordingly.The dynamic stability and intelligent control of the multi-station machine for ball pen tip production have been discussed. The main contents of the thesis are as follows:1) The situation of ball pen industries both at home and abroad are introduced. Meanwhile, the characteristics of their machines have been compared. In addition, the 24-staion machine tool with small power unit is studied, and the related parameters of its structure are also studied. 2) The critical speeds of the rotor system are obtained by the transfer matrix method, and the first and second order critical speeds are 2887.8 r/min and 8255.7 r/min respectively. It is also known the working speed of the rotating shaft of the small power unit is 4000～4500 r/min, being far from the critical speed. This means the rotor is running under the stability condition. Besides, the effects of the diameter of the rotor and clearance between two bearings on the critical speed have been discussed. Furthermore, the clearance of bearings, which has great influence on the working performance is analyzed according to the tribology theory.3) With multiple coupling faults, the nonlinear dynamic behavior of rotor-bearing system of the small power unit is complicated. Nevertheless, in this thesis the mechanism of the related coupling faults and mechanic characteristics are unveiled, and the shooting method is also put forward.4) Since the rotor-bearing structure with small clearness is an unstable system and in real condition the vibrational amplitude of the rotor, after destabilization, will increase until it reaches a certain value and hold still, the linear theory can't be used to solve this problem. So the nonlinear method is applied in this paper. The stability of rotor-bearing system of the small power unit was researched by nonlinear method, including the periodic solution and bifurcation.5) There are too many detected points, in the 24-station small power unit machine, to be detected by tradition method. In this case, the virtual instrument is adopted and the LabVIEW method is also used to design some parameters, especially the vibrational parameters. It is proved the invented detective system, consisting of virtual instrument and the LabVIEW method, is very helpful in practice and will be useful for further study.6) The optimization control model is established and related dynamic optimization is made for the system. Besides, the control of the 24-station machine tool is also carried out.In this project, the nonlinear method is used successfully to analyze the dynamic behavior and stability; the invented instrument is used in the online system; the optimization control system is used in the 24-station machine with small clearance of motive power.All of these works would push forward the research and development of the ball pen manufacturing machine as well as its industry. |
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