1 Advantages of resin grinding wheel grinding steel balls
The main components of resin grinding wheels are abrasives, resins, wetting agents, etc. They are characterized by finer grain size, higher hardness, uniform and dense internal structure, regular appearance and accurate size. Due to the elasticity of the resin grinding wheel, the pressure on the steel ball during the grinding process is small. Under similar grinding conditions, the steel ball processed by the resin grinding wheel with the grinding and grinding process has higher precision and surface quality than the steel ball ground by the cast iron disc. Good, the vibration value is low, and the mute effect is good after the bearing is fitted. In addition, the resin grinding wheel has high grinding efficiency, and its production efficiency is more than double that of cast iron discs. Although the price of the resin grinding wheel is higher than that of the cast iron disc, its processing efficiency is high, the grinding wheel is durable, and its overall cost is lower than the grinding cost of the cast iron disc. At the same time, the special grinding fluid (oil) for resin grinding wheels is more environmentally friendly, and the surface of the steel ball after processing is easy to clean.
2 Selection of resin grinding wheel grinding machine
The domestic resin grinding wheel is carried out on a vertical ball grinding machine with the grinding instead of grinding process. Because the grinding plate of the vertical machine tool is placed horizontally, the grinding debris falling off the resin grinding wheel during the grinding process is embedded in the grinding groove, relying on the grinding fluid The flushing is difficult to rule out. Therefore, the difficulty of chip removal has become a difficulty for the resin grinding wheel of vertical machine tools to replace the research process with grinding.
For this reason, the horizontal machine tool has become a machine tool for grinding steel balls with resin grinding wheels. The 3M77 series steel ball grinding machine adopts a horizontal layout and an open overall design. The design of the bed and head frame adopts the modular design of the high and low combination (low weight L-shaped structure) guide rail, which improves the strength and rigidity of the machine tool. The bed adopts special craftsmanship in processing, which eliminates potential deformation and fully guarantees the coaxiality and parallelism of the machine tool. At the same time, a special spindle structure and technological means are adopted, and imported bearings and optional installation are adopted, which greatly improves the rotation accuracy of the spindle and is stable for a long time. It provides a prerequisite for the resin grinding wheel to process high steel balls by grinding instead of research. The movement of the spindle headstock adopts rolling linear guide rail positioning, and the machine tool has high repeat positioning accuracy, which overcomes the change of the parallelism of the two discs at different positions during the pressurization process of the machine tool caused by the positioning of the cylinder. The application of the separation of the pressurization and sliding mechanism of the machine tool greatly improves the rigidity and stability of the whole machine, and provides a guarantee for batch processing of G5 and even G3 grade low-noise steel balls. The electric and hydraulic systems of this series of machine tools adopt advanced frequency conversion control technology and electro-hydraulic proportional adjustment technology, which can realize three-level program control conversion of initial pressure, intermediate pressure and fine pressure. Pre-set processing parameters such as pressure and time according to the process route, realize automatic conversion during work, and greatly improve production efficiency.
The 3M77 series horizontal machine tool adopts the resin grinding wheel of a Japanese company, the size is 800 mm×420 mm, 660mm×420mm, the thickness is 30 mm and 50 mm, the commonly used particle size is 2000#, 3000#, 4000#, the organization number is 9, and the adhesive It is BZ (long life) and BZL3 (good cutting performance), and it is well used.
3 Selection of resin grinding wheel
Although the resin grinding wheel grinding and grinding steel ball technology has been used, due to insufficient understanding of the resin grinding wheel, there are many misunderstandings in the selection of resin grinding wheel grades and organizational structure, so that the ideal steel ball grinding processing effect is not achieved.
The selection of the special resin grinding wheel for steel ball grinding should be determined according to the material of the steel ball, the grinding method, the grinding parameters and the processing accuracy, and the production efficiency. First select the appropriate resin grinding wheel label, including abrasive, particle size, bonding degree, bonding agent, organization and the size of the grinding wheel. When selecting a resin grinding wheel, it is necessary to consider both its grinding ability and workpiece grinding accuracy. The resin grinding wheel must have moderate durability, but also ensure a small amount of consumption, and always maintain good self-sharpening. Then formulate a reasonable processing technology according to the selected wheel mark to ensure the uniformity of the grinding pressure.
In the processing of steel balls, ceramic grinding wheels (WA/C 180Z ~ 320Z) are generally used in the initial process, resin grinding wheels (WA500Z ~ 2000Z) are used in the intermediate process, and resin grinding wheels (WA3000Z ~ 6000Z) are used in the process.
4 Selection of grinding fluid and filter system
Choosing the right grinding fluid, strictly controlling the temperature of the grinding fluid (oil), and preparing a suitable filter system are very critical in the grinding process of the resin grinding wheel. Due to the finer particle size of the resin grinding wheel, the grinding debris, abrasive particles, bonding agent, etc. produced during the processing are often embedded in the gaps between the grinding wheels and the grinding wheel loses its cutting ability. Under normal circumstances, a soft grinding ball is used for string grooves to eliminate the fatigue layer of the grinding wheel groove. Therefore, when choosing a grinding fluid, it is necessary to consider both its machinability and its cooling, lubricating and cleaning properties. Secondly, the filtration and cleanliness of the grinding fluid is also particularly critical. The impurities that may be generated during the grinding of the steel ball by the resin grinding wheel include: the shedding of the grinding wheel abrasive; the iron filings under the grinding of the steel ball; the impurities in the cutting fluid flowing through the channel Objects, dust, paint, etc. The current resin grinding wheels are mainly imported from Japan, most of which are 2000#, 3000#, 4000#, and 6000#, which are equivalent to the particle size of my country's grinding wheel powder W10, W7, W5, W2.5. This requires the filtration accuracy to basically reach about 10~2μm, and the filtration system provided in China still needs to be improved, especially the system filtration problem caused by the resin grinding wheel grit shedding, which is still a key factor affecting the further improvement of the quality of steel balls. Compared with the grinding of cast iron discs, the chemical properties of the cutting fluid have undergone great changes. The content of physical impurities in the cutting fluid and the size of the particles are not the same; this has a relatively more impact on the surface of the steel ball and the vibration value. Larger is more direct, so it is very important to choose an ideal filtration system. In addition, the temperature control of the grinding fluid (oil) is also very important. According to a Japanese company, the temperature control of the grinding fluid (oil) in the resin grinding wheel grinding of steel balls abroad is very strict, generally around 25 ℃.
5 Bonding, installation and dressing of resin grinding wheels
When resin grinding wheel is bonded, the grinding wheel must be cleaned first, and then bonded with glue, otherwise it will be difficult to bond firmly.
The dressing of the rotating grinding wheel is completed by the grinding wheel dresser. The dresser of the grinding wheel is hydraulically driven, which makes the diamond dresser perform linear reciprocating motion to complete the dressing of the grinding wheel. Adjust the diamond dressing block to make it level to ensure that the surface of the grinding wheel is smooth. The dressing of the fixed grinding wheel needs to be removed from the machine tool.