Sammanfattning: Med den snabba utvecklingen av precision och ultra precision bearbetning teknik, precision höghastighets elektrisk spindel teknik har också blir populär. Som en viktig gren av elektrisk spindel teknik forskning, vatten smörjd keramik glidande lager har blitt a större banbrytande forskning ämne i fältet av precision bearbetning. Denna artikel sammanfattar de egenskaper och fördelar av höghastighets elektriska spindlar stöds av vatten smord keramik glidande lager jämfört till vanligt glidande lager. It introducerar den strömmen forskning status av denna teknik på hemma och utomlands, och analyser och utforskar flera relaterade tekniker för den utvecklingen av vatten smord keramisk glidande lager.
Nyckelord: elektrisk spindel; vatten smörjning; keramik material
0 Förord
As one of the cutting-edge technologies in mechanical manufacturing, precision and ultra precision machining technology, due to its involvement in various basic disciplines and emerging technologies, has become the key to developing other high-tech industries and an important indicator of a country's manufacturing level. As an important support for precision and ultra precision machining technology, high-speed precision electric spindle technology naturally develops rapidly. In recent years, the hydraulic floating sliding bearing electric spindle has been highly favored in manufacturing enterprises due to its high rotational accuracy and ability to greatly improve the service life of cutting tools, as well as the machining accuracy and surface roughness of workpieces. However, ordinary liquid floating sliding bearings often encounter poor thermal stability of machine tools due to high temperature rise of lubricating oil film, high thermal conductivity of metal friction pairs, and large thermal expansion coefficient, which subsequently affects actual machining accuracy and makes it difficult to continue to adapt to the rapid development of high-precision technology. In theory, water generates less heat when bearings rotate at high speeds, and its inherent cleanliness and flame retardancy can meet the safety and environmental friendliness requirements of modern society for engineering technology; In addition, ceramic materials have the characteristics of wear resistance, which can adapt to boundary friction and dry friction phenomena that easily occur under water lubrication. Ceramics also have excellent characteristics such as chemical corrosion resistance and low thermal expansion coefficient. In this way, water lubrication combined with ceramic material friction pairs can solve the technical problems of ordinary liquid floating sliding bearings. As a result, water lubricated ceramic sliding bearings have gradually become a major cutting-edge research topic in the precision machining industry today.
1 Egenskaper av Vatten Smord Keramik Glidning Lager Elektrisk Spindel
Denna typ av elektrisk spindel stöds av keramik glidande lager% 2c och dess struktur är liknande till det av allmänt glidande lager elektriskt spindlar% 2c som visas i figur 1. dock% 2c på grund av den speciella naturen av dess lager smörjmedel och friktion par% 2c den övergripande prestanda av spindeln är förbättrad i många aspekter.
Figure 1 Structure of an ordinary electric spindle
Firstly, this type of electric spindle uses water (or low viscosity water-based liquid) as a lubricant. By comparing water with L-FD-22 bearing oil, as shown in Table 1, it can be found that the significant difference between water and ordinary mineral lubricating oil lies in its viscosity and specific heat [3]. It can be seen that the viscosity of water is much lower than that of ordinary mineral oil, which results in lower oil film stiffness and bearing capacity of water lubricated bearings compared to oil lubricated bearings under the same state. Moreover, dry friction caused by direct contact of friction pairs is prone to occur, which requires bearing materials to have high wear resistance; However, due to its low viscosity, water can significantly reduce friction power consumption, thereby reducing bearing temperature rise and improving the rotation accuracy of the spindle. At the same time, the specific heat of water is significantly higher than that of mineral oil, resulting in a smaller temperature rise under the same friction power consumption and heat generation. Therefore, when the spindle rotates at high speed, the thermal stability of this type of spindle is more prominent.
Tabell 1 Jämförelse av prestanda indikatorer mellan vatten och smörjning olja
Vatten själv har renhet och flam retardans, och är a naturlig kylande och släckande medel. I den 21:a århundradet, med ökande uppmärksamhet till miljö och säkerhet frågor från alla sektorer av samhälle, denna egenskapsmässigt exakt uppfyller den säkerhet och miljö krav av modern samhälle i det fältet av teknik teknik.
On the other hand, the materials used in the research of water lubricated bearings so far mainly include wood, metal, plastic, rubber, and engineering ceramic materials. Among them, due to the excellent wear resistance of engineering ceramic materials, it is possible to use them as friction pairs in a low viscosity lubricant state [4]; In addition, ceramic materials generally have many advantages such as self-lubricating function, high temperature resistance, high hardness, high strength, low friction coefficient, and good thermal stability. Using ceramic materials as friction pairs can also correspondingly improve the overall performance of the spindle. In recent years, they have gradually been applied in the industrial field.
2 Forskning och Utveckling Status
2.1 Research on related ceramic materials
De vanligtvis använda teknik keramik material huvudsakligen inkludera oxid typ A12O3, ZrO2, och icke oxid typ SiC, Si3N4, vilket har olika friktion och slitage mekanismer under torr friktion och vatten smörjning förhållanden. När torr friktion inträffar, den friktion prestanda av keramik friktion par är avgörande; När den vatten film i den lager är intakt, vätskan friktion effekten av den keramiska friktion paret kommer vara mycket uppenbar [3% 5d. Men, under vatten smörjning förhållanden, tjockleken av den smörjningen vätska film är relativt liten, vilken är benägen till torr friktion. Därför, båda tillstånd behöver till vara anses.
I den torr friktion tillstånd, det kan vara hittat genom experiment det oxid keramik A12O3 och ZrO2 är benägen till spröd fraktur och slipmedel slitage, medan slitage beteende av icke oxid keramik SiC och Si3N4 huvudsakligen inkluderar mikrosprickor, plast deformation, plöjning, och vidhäftning. Men, Si3N4 är benägen till friktion skikt migration, och SiO2, a biprodukt av SiC in den friktion process, har a viss smörjning effekt, vilken kan minska slitage och friktion koefficient, So från den torr friktion tillstånd ensam, SiC är mer lämplig som a friktion par material.
Under the action of fluid friction, oxide ceramics have a significant fluid lubrication effect, among which the Al (OH) 3 generated by A12O3 during the process is more helpful in improving its wear resistance. Non oxide ceramics SiC and Si3N4 not only have fluid lubrication effect, but also produce obvious hydration reaction [5], forming colloidal SiO2 attached to the friction pair surface, which has the effect of polishing the surface and can significantly improve surface wear. However, the superiority and inferiority of SiC and Si3N4 materials have not been reflected in the experiments conducted by different researchers under different operating conditions. Overall, Si3N4 requires a shorter running time to reach a stable state, and SiC is more suitable for long-term operation or frequent starting and stopping conditions. Therefore, specific experimental analysis is needed to determine the choice after Z.
2.2 Spindel Test Forskning
At present, domestic experts and scholars as well as relevant enterprises have done a lot of research on the operation of water lubricated bearings, such as bearing performance, machining accuracy, friction chemical behavior in bearings, etc., but most of the research is mainly to carry out Test effort to verify that the water lubricated ceramic sliding bearing spindle can achieve the goals set by the test or required by the enterprise, For example, experimental research conducted by Zhang Guoyuan et al. on the hydrodynamic and hydrostatic bearings of water lubricated turbopumps has shown that water lubricated bearings can operate stably at high speeds without significant vaporization or cavitation. On the other hand, there are currently few experimental studies on the design optimization of water lubricated ceramic sliding bearings, among which STEVEN [7] adopts a new feedback throttling technology Sun Wenli et al. [8] broke through pure water and water-based lubricants when choosing lubricants, and adopted equilibrium solutions of various salts such as seawater. The "metal ceramic" fully enclosed structure designed by Lin Bin et al. [9] played an important role in further optimizing and applying water lubricated ceramic sliding bearings.
2.3 Application of Water Lubricated Ceramic Bearings
At present, due to the fact that water lubricated ceramic bearings are still in the research and optimization stage in terms of lubrication fluid and frictional chemical reactions of ceramic material friction pairs, there has not yet been a machine tool spindle unit supported by water lubricated bearings in China, but experimental engineering applications have begun abroad. For example, the HF170 HA-40HKV machine tool electric spindle, developed in collaboration with Swiss IBAG and Nintherur Technical University, is supported by water lubricated static pressure bearings. Its improved labyrinth and air seal system can effectively prevent water leakage from the bearings, with a speed of up to 40kr/min and a power of 37kW. The Hrdro-F electric spindle produced by FISCHER uses water lubricated static pressure bearings, with a speed of 36kr/min and a power of 67kW. The successful cases of foreign enterprises reflect the possibility of water lubricated ceramic spindles entering enterprises and promoting practice, which in turn promotes research by researchers to solve technical problems such as high processing and manufacturing accuracy that are difficult to achieve.
3 Development related technologies of water lubricated ceramic sliding bearings
3.1 Dynamic and static pressure technology
There are three main types of ordinary liquid sliding bearings for electric spindles: static pressure bearings, dynamic pressure bearings, and dynamic static pressure bearings. The obvious difference lies in the order of magnitude of the depth of the bearing oil cavity. Among them, dynamic and static pressure bearings are developed on the basis of the other two types of bearings. These types of bearings mainly rely on dynamic pressure at high speeds and static pressure at low speeds (starting and stopping stages). It utilizes the throttling principle of static pressure bearings to generate sufficient static pressure bearing capacity in the pressure oil chamber, thereby overcoming the wear phenomenon between the main shaft and bearings caused by dry friction during the start and stop of liquid dynamic pressure bearings, improving the service life and accuracy maintenance of the main shaft and bearings. At the same time, it also utilizes the dynamic pressure effect of the main shaft during high-speed rotation to reduce liquid energy consumption. Therefore, as long as the oil chamber parameters are reasonably designed and precision machining methods are used, the load-bearing characteristics of dynamic and static bearings can be utilized to be superior to the other two types of bearings, thereby compensating for the impact of lower viscosity of lubricants on their performance.
3.2 Theory and Structural Design
At present, the design of most sliding bearings adopts the method of establishing appropriate Reynolds equation according to the requirements of specific working conditions. However, since the general Reynolds equation is applicable to laminar flow, and the viscosity of water is small, it is easy to produce turbulent flow, so the generalized Reynolds equation should be used to solve it [10]; At the same time, considering the design of electric spindles for precision and ultra precision machining, the impact on temperature, pressure, and other factors cannot be ignored. Excessive temperature and pressure of the lubricating fluid film can cause surface deformation of the friction pair, while the thickness of the lubricating fluid film can affect the surface roughness of the friction pair. In recent years, the TEHD (Thermoelastic Fluid power Lubrication Analysis) model has been gradually accepted because it is closer to the actual situation. When this model is used in the calculation of water lubricated ceramic sliding bearings, the thermal and elastic deformation of ceramic bearing pads should be taken into account at the same time. Specifically, the viscosity temperature relationship, density temperature relationship, energy balance equation, continuity equation, etc. should be integrated when solving the Reynolds equation. In addition, the structure of bearings has a significant impact on the performance of bearings and even the spindle. Therefore, many researchers have attempted and tested in this regard, such as the fully enclosed structure mentioned above, which has achieved successful testing, ensuring rigidity while achieving a bearing capacity of over 3 tons.
3.3 Lubrication related technologies
Due to the non rost resistance of water, in practical research, vattenbaserad rost inhibitorer är generellt tillsatt till vatten till form ny låg viskositet vattenbaserade smörjmedel. Allmänt, tillsatser bör säkerställa tillräcklig löslighet under arbetsförhållanden till förhindra nederbörd från orsaka friktion yta skada; In addition, överväga att tjockleken av den smörjning film är relativt liten vid låg viskositet och den sannolikheten av mekanisk friktion är hög, aktiv design och konstruktion av geometriska former kan vara övervägd under design, och teoretisk certifiering kan vara genomförd före bearbetning och tillverkning.
3.4 Tillverkning och Testning
På grund av till faktum att keramik material är hårda och spröda % 2c tillverkning bearbetning svår% 2c och glidande lager (särskilt dynamisk och statisk tryck lager) kräver hög dimensionell noggrannhet för lager skal% 2c bussningar% 2c och olja håligheter% 2c precision bearbetning har alltid varit en viktig aspekt som begränsar utvecklingen av vatten smörjd glidande lager. Även om precision och ultra precision bearbetning verktyg och relaterad teknik är snabbt utveckla, det är fortfarande nödvändigt för att ytterligare hitta tillräckligt exakt och lämplig fabrik bearbetning metoder.
Experimentell teknik är en oumbärlig teknik som åtföljer den utvecklingen av spindel design teknik. Fastän den experimentella tekniken av vanliga glidande lager har allmänt blir mogen, på grund av den särdraget av vatten smord keramik spindlar, uppmärksamhet bör betalas till övervakning till synes vanliga miljöfaktorer sådana som vatten temperatur och tryck på den grunden av vanliga experiment. At the same time, advance testing and testing should also be conducted on the various properties of the ceramic materials used, Ensure that it meets the processing and manufacturing targets.
4 Sammanfattning och Outlook
Baserat på den föregående text, det kan vara sett det på grund av till dess olika fördelar, där är a stor möjlighet att vatten smörjt glidande lager kommer vara brett används i framtid precision höghastighets elektriska spindlar, som har också mottagits utbredd uppmärksamhet. Fastän där finns för närvarande nej produktion praxis i Kina, vi tror att med den signifikant framsteg gjort utomlands, människor kommer att investera mer energi i forskning och testning relaterade tekniker. Vi blicka framåt till bryta genom begränsningarna i teoretisk design och bearbetning tillverkning av vatten smörjd keramik glidande lager, och arbeta tillsammans med relevant spindel tillverkning företag till uppnå praktiska, marknad, och industrialisering som snart som möjligt.
MG-CR Filament Lindad Plast Självsmörjande Lager:
Hög styrka glas fiber med epoxi harts bakad med PTFE och special fiber som lager foder, baksida material ger hög belastning kapacitet och lager foder ouers låg friktion under torr tillstånd. Därför, denna special struktur ouered an enastående slitage funktion och anti-slag prestanda, lämplig för hög belastning med hög korrosion beständighet applikation liknande lyft maskiner, logistik maskiner, jordbruk maskiner, Lantbruk maskiner, och port maskiner etc.
https://www.marginalbearings.com/filament-wound-plastic-self-lubricating-bearings/mg-cr-filament-wound-plastic-self-lubricating.html
