Application of CBN grinding wheel in grinding
Jan 16, 2020

In addition to the use of CBN materials for cutting tools, the largest application area is CBN grinding tools, which are used for high-speed and efficient grinding and honing, which can greatly improve grinding efficiency and improve grinding accuracy and quality by a level.

1.Grinding automotive parts--camshaft and crankshaft

The camshaft on the automobile engine has multiple cams. The rough grinding and fine grinding of the cam after quenching are the key processes that affect the quality of the cam. Generally, imitated shape grinding is used, and the increase of the workpiece speed is limited, and the workpiece is prone to generate grinding burn cracks. Using imitated shape grinding, the cam profile of the cam surface is affected by the diameter of the grinding wheel, so it is difficult Ensure that the cam profile is correct. Production practice proves that when the diameter of the grinding wheel is large, the cam that is ground is thin, and when the diameter of the grinding wheel is small, the ground cam is fat. Only when the diameter of the grinding wheel is close to or equal to the diameter of the roller for grinding the cam (usuallyφ570mm), The profiling error is close to zero, that is, the cam surface profile of the ground cam is close to the master cam. In actual production, the diameter of the grinding wheel used is generally from D600 (or 610) to D500, which is much different from the ideal grinding wheel diameter (570), so the cam curve of most camshafts in production always exceeds the standard. To solve this problem, we use CBN grinding wheel grinding on the cam cam grinding machine. The diameter of the CBN grinding wheel can be made as D575. The thickness of the CBN abrasive layer is 4 ~ 5mm. The minimum diameter of the grinding wheel is D565. Although the range is only 10mm, the number of grinding parts is equivalent to dozens of ordinary grinding wheels, which not only ensures the correct cam curve, but also does not produce grinding burns.

For example, Liton Industrial Automation Co., Ltd. uses aCBN grinding wheelto grind acamshaft, which reduces the cost by 50% and increases the fatigue strength of the cam surface by 30%. Dongfeng Motor Corporation's Xiangfan Diesel Engine Plant uses a ceramic bond CBN grinding wheel to rough grind cold-chilled cast iron camshafts. , Its cam grinding allowance t = 4~5mm,υsand = 60m / s, workpiece speed n = 100r / min,υf = 0.1mm / s, using high-speed grinding fluid, the life of CBN grinding wheel is basically equivalent to 20 pieces Corundum abrasive wheel.

2.Application of CBN grinding wheel in inner hole grinding

The efficiency of internal grinding has always been very low. The main reasons are the grinding speed, the material of the grinding wheel and the rigidity of the grinding rod. The time spent in dressing and changing the grinding wheel during the production process accounts for almost one-third to one-fifth of the man-hour. If inner circle or groove grinding adopts CBN electroplated grinding wheel, and increase the grinding wheel speed and increase the diameter of the grinding rod, the workpiece rotation speed and feed speed can be appropriately increased, and not only the hole (arc) diameter, groove width size and shape can be guaranteed Bit accuracy, surface roughness and avoiding burns, but also can double the processing efficiency and reduce processing costs.

For example, a domestic factory processed a rolling bearing sleeve for a textile machine with an annual output of 600,000 pieces, grindingφ15.5 + 0.04 holes and adjacent arc grooves. In the past, chrome corundum (GG) grinding wheels were used. M224 internal grinding machine, the groove (arc) diameter difference and the coaxiality of the size and the hole are difficult to ensure, and the efficiency is low. After using the CBN grinding wheel, the grinding rod is thickened, the feed is increased, and the trimming is saved And the time of changing the grinding wheel completely solved the original problem. Later, it was changed to simultaneous grinding of holes and grooves, that is, two grinding wheels were installed on the grinding rod, which doubled the grinding efficiency and saved a grinding machine. The surface roughness of the processed workpiece is Ra0.63μm. The grinding process parameters used are:υsand = 36m / s,υ2 = 19m / min, f rough cut = 1μm / r, f fine cut = 0.5μm / r, light grinding Time t = bs, using 10% concentration emulsification value.

CBN grinding wheels

3.Grinding gear with CBN wheel

Gear grinding has traditionally used single-toothed and multi-toothed surface grinding. Although single-toothed surface grinding can achieve high machining accuracy, it is low in efficiency and high in cost. Although multi-toothed surface grinding has high production efficiency, its processing Quality is worse than single tooth grinding. If the CBN grinding wheel is used for grinding, whether it is single-toothed or multi-toothed, grinding with electroplated CBN or ceramic bond grinding wheels will have significant effects:

(1) CBN grinding wheel can be made into tooth profile with high precision. Due to its high durability and infrequent trimming, it is not necessary to adjust the machine tool frequently to obtain stable tooth frame, lead and pitch accuracy.

(2) High-speed grinding and high-feed-rate grinding of tooth surfaces can be achieved, with low roughness and no burns, and high gear accuracy (grades 6 to 7) can be obtained under conditions that improve grinding efficiency.

(3) The CBN grinding wheel has a long life and good grinding performance, which saves a lot of auxiliary time such as grinding wheel replacement and dressing, machine tool adjustment, and workpiece inspection.

4.Application of CBN abrasive tools for difficult-to-machine materials and difficult-to-machine surfaces

For honing hardened steel or cold hard cast iron holes, CBN honing stones can be used. For high-strength, high-hardness and high heat-sensitive alloy steels, stainless steels, heat-resistant steels and alloys, high-hardness and high-strength CBN should be used. Grinding wheels are cooled by extreme pressure emulsion or high speed grinding fluid. CBN grinding wheels should be used for longer guide surfaces or complex profiles, and the master shaft of cam grinders.Promote the application of CBN materials in key processes of machining.

CBN materials can be used to produce cutting tools or grinding tools for high-speed cutting or grinding, and can receive significant effects such as improving product quality, improving processing efficiency, shortening processing cycles and reducing processing costs. Therefore, in processing, vigorously promoting CBN tools (grinding tools) is a powerful measure to improve manufacturing technology. However, if it is widely used, there are still many problems.

In order to better promote the use of CBN knives (grinding tools) in production, the following aspects should be done:

  • Give play to the leading role of CBN Knife (Abrasive) Research Institute (Institute)

At present, there are many domestic CBN material manufacturers and a lot of output, but there are not many high-quality products, and there are fewer stable users of CBN knives (grinding tools). The main reason is that the mechanical processing department lacks the knowledge of the selection and use of expensive CBN tools (grinding tools), and the purchased CBN tools have little practical effect. Under the conditions of economic contraction, they are afraid to invest in process tests easily. In order to solve this problem, only the CBN Knife (Abrasive) Research Institute (Institute) actively enters the manufacturing unit of machinery manufacturing, selects weak points of production efficiency and quality, and has points that are or are easy to create CBN processing conditions, and negotiates with users. Signed a joint development CBN application contract. The tool development unit is responsible for providing the CBN knife (grinding) tool for testing at no charge, and the user is responsible for providing the production test under the conditions required for the test. This has exerted the enthusiasm of many parties. From CBN quality selection to tool manufacturing, it will be carried out at the optimal and fastest speed. From the preparation of test conditions to the use, the user has seen the results of reaching the contract target value, and it is resolved without spending test costs. Production problems are easy to promote. The tool institute (institute) can also gradually recover profits in the future supply. As long as the two parties maintain reciprocity and mutual benefit, the cooperative relationship will be further consolidated. Our factory uses this method to develop many new technologies with a number of research institutes.

  • Realize three-point and one-line joint development, that is, CBN-tool manufacturing-users or CBN and tool manufacturing-machine tools-users jointly develop CBN applications

Although many machining difficulties in mechanical processing can be solved with CBN tools, at present, it is not something that can be done by any domestic company, because not all CBN tools have peculiar and versatile processing capabilities. We have also used CBN inserts for fine boring cylinder liners, and the results are not better than new ceramic inserts. The reasons are various, such as whether CBN quality, content, brand specifications, and binders are suitable for the processing of boron cast iron. As for the factors that affect the grinding effect of CBN abrasives, there are more factors. In addition to the quality of the raw materials, the ratio and the manufacturing technology of the abrasives, there are also conditions and technologies for use. Such as grinding speed (application of high-speed grinding speed), good rigidity of the grinding machine, no vibration, automatic fine feed and dressing compensation mechanism, appropriate grinding parameters and coolant, etc. These are important factors that complement each other and depend on relevant parties Working together to improve the quality of their own products and promote each other, can CBN tools and special equipment be successfully used in production.

  • Actively carry out research on CBN knife (abrasive) tool manufacturing and use technology

Users want to use effective CBN tools. To this end, the tool manufacturing unit is required to, in addition to improving the manufacturing technology of CBN tools as soon as possible, establish clear identification standards and methods for product quality, and distribute certain performance parameters, such as the CBN of the tool. Content and brand, hardness and CBN accuracy, concentration, etc. of the production and use test on this basis, in order to give full play to the user's production experience, compare and analyze the processing results obtained by different cutting parameters and coolant, so that CBN tools have been qualitatively improved. The scope of CBN tools, the conditions of use, and the technical support of the application (such as equipment and coolants), users can choose and use CBN tools correctly.

  • Users need to improve product quality awareness and have the courage to improve manufacturing technology

The 21st century is a high-tech era. Products must have high performance and high quality in order to have a market, and enterprises can have vitality. To this end, the level of manufacturing technology should be improved as soon as possible, and the promotion of the use of CBN tools to improve manufacturing technology is a powerful measure. This requires not only the strong funding and support of relevant authorities, but also the systematic and systematic promotion of CBN tool technology and The use also requires users to be brave to accept new materials and new technologies, and change the old production concepts and management methods in the past. That is, the average consumption cost of knives (grinding tools) is very low, which can only account for about 1/100 of the product cost, not Based on improving production efficiency and ensuring product quality, this will limit the use of high-quality and efficient knife (abrasive) tools and the production of advanced equipment. Practice has proved that the effectiveness of CBN cutters (grinding tools) can not only improve the processing quality of products, but also improve economic benefits.

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