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New skills of bearing ring grinding and super processing and its development at home and abroad
Source: China Bearing Network Time: 2013-05-25
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Foreign bearing industry; 60 era has formed a stable ferrule grinding super-processing process and fundamental approach; namely: double-face grinding centerless cylindrical grinding raceway cutting into centerless grinding raceway super-finishing processing. In addition to the special layout Bearings; demand is attached to a number of processes; many produced ferrules are processed according to this process. For decades, the process has not changed fundamentally; however, this does not mean that bearing production skills have not been carried out. Briefly In the 60th era, only the process of “double-end centerless circular cutting into the grinding and super-finishing†was established and carried out; and a series of cutting-in centerless grinding machines and super-finishing machines were born accordingly; the machining accuracy of parts reached 3~5um; Processing time 13 ~ 18s (small and medium-sized scale). The 70th era is mainly based on the use of 60m / s high-speed grinding, control grinding skills and control grinding machine; a digital control skills of electronic control skills characterized by integrated circuits It has been selected a lot; then it has improved the stability of the grinding machine and the process; the machining accuracy of the parts has reached 1~3um; the parts processing time has been 10~12s.80 times; the process and equipment Machining accuracy is not the problem; the primary direction is carried out under conditions of stable quality; seek higher power; adjustment more convenient and CNC production and automation systems.
2. The grinding of the bearing ring is in the production of the bearing; the grinding labor accounts for about 60% of the total labor; the number of grinding machines used is also about 60% of the total metal cutting machine; the cost of grinding accounts for the entire bearing cost. More than 15%. About high-precision bearings; these parts of grinding processing are bigger. Others; grinding processing is the most messy in the whole processing process; it is still the most inexpensive one. It is still a messy table. Nowadays, the required functional indicators are more, the precision is higher, the processing and forming mechanism is more messy; there are many factors affecting the machining accuracy, and the processing parameters are difficult to be detected online. Therefore, the grinding process is one of the key processes in the bearing production; how to choose New technology; new skills; end the grinding process with high precision, high power and low cost; it is the primary task of grinding.
2.1 High-speed grinding skills High-speed grinding can end the two principles of modern production skills. Product quality and labor power. Practice has proved that if the grinding speed is improved from 35m/s to 50-60m/s; usually produced The power can be improved by 30% to 60%; the durability of the grinding wheel is improved by about 0.7 to 1 times; the roughness value of the workpiece surface is reduced by about 50%.
Generally, the grinding speed reaches 45m/s or more, which is called high-speed grinding. It is represented by the ZYS 811 full-active bearing internal grinding machine developed by our company in the 80th era. It is the first to use high-speed grinding in the domestic bearing professional ring grinding process. Skills; successfully developed high-rigidity, high-speed, high-power electric spindle and high-speed grinding wheel. High-speed grinding at home and abroad has been widely used; and it is widely used with high grinding ratio, high durability super hard abrasive such as CBN; Grinding speed has reached 80 ~ 120m / s; even higher. Such as: Germany Mikrosa, Japan KOYO company's centerless grinding machine; Japan TOYO company's bearing internal grinding machine; external and external grinding wheel speed of 120m / s; inside and outside Table grinding line speed of 60m / s ~ 80m / s.
Increasing the power of the grinding wheel drive (drive) system and improving the rigidity of the machine tool; it is an important measure to end the high-speed grinding; while the high-speed spindle unit is the most important part of the high-speed grinding machine. In high-speed grinding, the grinding wheel should be satisfied. In addition to strength; also need to ensure outstanding grinding function; to achieve high grinding effect. Others; cooling equipment is also one of the equipment to end high-speed grinding is not short.
2.2 CBN grinding wheel grinding technology Cubic boron nitride abrasive is referred to as CBN abrasive; the grinding wheel made by it is called CBN grinding wheel; it has the following characteristics: (1) High hardness; high thermal conductivity; good thermal stability; acceptable 1300~ 1500 °C high temperature. (2) High durability; wear. ãƒéž…瓤 4,000 ~ 10000 (grinding ratio refers to the ratio of the amount of workpiece data to the wear of the grinding wheel in the grinding process) and usually the corundum grinding wheel is only 50 ~ 80. (3) Grinding Cutting force. ム刃 .. ã™ãœ ã™ãœ απ. è¿é˜Œ α Ρ 蛎 .. (4) auxiliary time (dressing wheel, replacement grinding wheel) greatly reduced.
For China's bearing profession; the use of CBN for ferrule grinding is a new processing skill; the application of the vision is very broad; but the need to discuss the following skills: CBN grinding wheel production skills, finishing skills, special bearing grinding machine and grinding cooling Liquid, etc.
Because CBN grinding wheel has outstanding processing characteristics; the use of CBN grinding wheel for bearing ring grinding has been developed and used in production abroad; and it is called "a revolution in production and processing skills". Since 1982; CBN grinding wheel It has been used in large numbers in Japan; and it has increased at a high speed.
2.3 External and external surface grinding wheel active dynamic balance skills on external and external surface grinding; due to the large grinding wheel and non-homogeneous structure; the center of gravity of the grinding wheel system always violates the middle of the spindle; the high-speed rotation must incur the grinding wheel system and its entire machine tool The vibration directly affects the service life of the machine tool. In this case, the grinding process will be difficult to reach high precision; it is easy to cause the grinding surface of the workpiece to be worn; the waviness is increased.
Mechanical or other active dynamic balancing equipment on the machine wheel directly on the machine wheel; the speed is directly forced to the most balanced position after starting the machine; the active balance is perfect and the static balance of the wheel can be saved. The breaking of this skill promotes the grinding The development of skills; together can greatly extend the grinding wheel, trim diamond and spindle bearing life; reduce machine vibration; long-term adherence to the original accuracy of the machine.
2.4 The ability to quickly eliminate the internal and external grinding of the lost machining in all bearing grinding equipment; the level of the internal and external surface grinding machine has the meaning of the mark. This is mainly because the grinding aperture constrains the grinding wheel scale and the corresponding system organization mobilization parameters; It fundamentally constrains the rigidity of the process system; together with its high processing precision requirements, it is necessary for us to deepen the process of the internal and external surface grinding process; in addition to the maximum restraint to carry out the cutting ability of the machine tool and the grinding wheel; Reducing the auxiliary grinding time is the key to improving the grinding power; since the grinding dead time accounts for about 10% of the entire grinding time.
At present, the skills of using a wide range of speeds to eliminate grinding and emptying at home and abroad include the following: control force grinding skills; constant power grinding skills; using active measuring instrument skills and measuring electric spindle current skills.
2.5 CNC numerical control skills and communication servo skills communication servo motor and PLC programmable controller positioning module; servo amplifier connected to form a servo system; servo motor itself with optical rotary encoder; its output signal is reflected The servo amplifier can form a semi-closed loop control system. It can ensure the positioning accuracy at high speed (3000rpm) and low speed operation. The servo system can end the fast jump, fast trend, trimming compensation, rough grinding; Simplification; the reliability of the function is greatly improved.
2.6 Communication frequency control technology In the grinding, the linear speed of the grinding wheel gradually decreases with the consumption of the grinding wheel; the ratio of the starting speed to the final linear speed is about 3:2. Currently; the high line has been selected in the grinding wheel grinding category. Speed ​​grinding; in order to improve the grinding power and ensure the consistency of grinding quality; use the programmable controller to calculate the grinding wheel radius after each dressing wheel; and then calculate the input frequency of the inverter that adheres to the constant line speed of the grinding wheel; Transfer to the communication inverter; then ensure that the grinding wheel line speed does not change.
3. The super-finishing processing of the bearing ring is carried out from the middle of the 30th century; its creation is to align the bearing to the surface of the rolling; it is a fine and economical processing technology; followed by machining parts The continuous improvement of the fineness and appearance quality requirements; the ultra-finishing processing has become more and more widely used. It plays an important role in the finishing of the bearing production (polishing, abrasive belt grinding, super finishing and super finishing).
Super-finishing processing; referred to as “super-finishingâ€; usually refers to the excellent smooth condition; the workpiece is rotated at a certain speed; the oil stone elastically presses the workpiece to the outer surface according to a certain pressure; and rotates perpendicular to the workpiece The direction of the reciprocating vibration movement according to a certain rule, which can be actively finished.
The superfinishing process consists of three distinct periods of independent distinction: trimming, stable cutting, polishing (also divided into: during cutting or self-sharpening, half-cutting, finishing) and the entire process is fundamental Process parameters (such as cutting speed, oil pressure and hardness, vibration frequency, abrasive type, workpiece data, smooth coolant, etc.) are automatically terminated under the same conditions.
3.1 The advantages of superfinishing processing
3.1.1 can be useful to reduce the circular error (primarily waviness).
3.1.2 can usefully improve the linearity of the raceway busbar or process it into the desired crown shape.
3.1.3 can remove the grinding enthalpy layer; reduce the surface roughness value.
3.1.4 can make the appearance of the remaining compressive stress.
3.1.5 can form a texture that is even and delicate and more ambitious in the processing appearance.
3.1.6 can increase the touch area of ​​the work.
3.2 Influence of super finishing on the function of rolling bearing
3.2.2 The precision of the rotation of the progressive bearing; reduce the vibration and noise of the bearing.
3.2.2 The bearing capacity of the progressive bearing.
3.2.3 Progressive bearing smoothing effect; reduce wear.
3.2.4 Reduce the heat generated during bearing operation.
3.3 Super-finishing processing skills
3.3.1 Oilstone production skills It resolves the use of oilstone; it is the condition for the existence of super-finishing skills; the application of demand: oil stone cutting function is better; the loss is slow; there must be a satisfactory strength.
In the meantime; ceramics contact CBN super essential oil stone; can adhere to the constant high cutting rate; the amount of wear is very much. 俳缪沽 Ω 撸豢 èŸ ç‡å²£å–ãœ èŸ ç‡å²£å–ãœ èŸ ç‡å²£å–ãœ èŸ ç‡å²£å–㜠亢屯骋æ 亢屯骋æ 亢屯骋æ 金刚石 金刚石 金刚石 金刚石 金刚石 金刚石 金刚石 金刚石 金刚石 金刚石 金刚石 金刚石 金刚石 金刚石 金刚石 金刚石The highest cutting rate can be obtained; the minimum wear rate and the best appearance lapping effect. Cubic silicon carbide whetstone; similar to diamond cubic boron nitride; cutting force and processing quality are second only to the former two; Silicon high.
3.3.2 Super-finishing process skills Super-precision process The general super-finishing process is divided into two parts: coarse super and fine super. During the rough super period, the oil-stone abrasive is sharper; the oil stone pressure is higher; the workpiece rotation speed is lower; The pendulum frequency is higher; therefore, the cutting force is strong; it is the first period to remove the workpiece processing amount. The oil stone abrasive is relatively passivated during the fine super period; the oil stone pressure is lower; the workpiece rotation speed is higher; the swing frequency is lower; The polishing effect on the surface of the workpiece is strengthened; the roughness value of the surface is greatly reduced.
In the meantime; one-stage two-segment method; one-sequence two-step method; oil stone active compensation skills; oil stone active supply skills; rough, fine super oil stone active change skills and high-frequency small vibration plus low-frequency reciprocating skills are all on domestic or foreign equipment Some use.
3.3.3. Work positioning technology The current workpiece positioning methods commonly used in the raceway superfinishing machine are as follows: mechanical clamping of the end roller mechanical clamping; hydraulic clamping of the hydraulic centering roller; double roller drive End face compression type without heart clamping.
3.3.4 Smooth cooling skills Super-finishing smooth liquid first three effects: scouring cooling; smooth; constitutes the adsorption oil film.
Ultra-finishing needs for smooth cooling: proper viscosity; rust-proof function; volatility.
Ultra-finishing has severe requirements for the filtration accuracy of smooth coolants; therefore, it is necessary to have high-precision filtration equipment to ensure.
In summary, the Process Tooling Professional Committee surrounds the needs of the “10th Five-Year†project of the Central Axis Association Skills Committee; builds a fine roller bearing;
1. The grinding of the bearing roller and the super-difficult problem. The super-precision skill of the logarithmic curve of the roller crown has been successful in the “Eighth Five-Year Planâ€; the current priority is to promote the application and progress of the reliability and stability of the ultra-precision system.
2. Developed and improved the ferrule raceway crown super-precision machine. Although this skill study has achieved certain results, the leading level of the gap to reach SKF company is still a certain interval.
3. Developed with the skills and equipment of the convexity of the file.
4. Roller end face super-fine skills research and equipment development.
5. Promote the industrialization of new oilstones and the use and application.
6. Applying the above-mentioned leading and latest patented skills to the roller bearing's grinding equipment upgrade and the development of a new generation of equipment, together with the development of the roller bearing's active production assembly line.
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