Led Area Light,200W Led Area Light,Led High Area Light,Dlc Area Lights Fuonce-Lighting , https://www.fuoncelighting.com
High-precision narrow-deep grooves have always been a problem in machining. Previously, narrow depth grooves of >2 mm in width on common material parts were usually pre-milled with a slit milling cutter and then heat treated and then ground with a thinner resin or ceramic bond wheel. This process has low processing efficiency, low wheel strength, poor rigidity and short life, making it difficult to achieve high machining accuracy. The ordinary grinding wheel is used for the grinding process, and the high precision narrow groove can be processed by grinding the workpiece after heat treatment. For narrow and deep grooves with width <2mm, the cost is high and the precision is low during milling. When grinding with ordinary grinding wheel, the working part of the grinding wheel is thin, the dressing amount is large, and it is easy to be broken during grinding and dressing. Processing costs are high. In recent years, electroplated superabrasive grinding wheels have been widely used for slow-feed grinding of high-precision grooves. Foreign countries have used the electroplated CBN grinding wheel to slowly drill a narrow deep groove with a width of 1.52 mm, a depth of 6.35 mm and a rounded corner of 0.38 mm on a 4340 steel piece of hardness HRC42. In China, the CBN grinding wheel is also used to slowly drill a narrow depth groove of 1.5 mm wide on ordinary steel. Many aerospace parts made of difficult-to-machine materials have a variety of high-precision grooves, especially the machining of high-precision cogging and narrow-deep straight grooves in the turbine blade roots, which has been a difficult point in domestic blade processing. This paper will introduce the design of the grinding tool base for the grinding of narrow and deep grooves by electroplating CBN grinding wheel.
1 radius design of the base of the grinding tool
As the speed of the grinding tool increases, the roughness of the grinding surface decreases, which is because the increase of the grinding wheel speed causes the single abrasive grain to be undeformed and the thickness of the grinding debris to be reduced. High-speed grinding increases metal removal rates, reduces grinding forces, reduces power consumption, and improves grinding efficiency. Increasing the speed of the CBN tool can improve the surface roughness of the workpiece; the higher the speed of the tool, the better the surface roughness of the workpiece, the lower the tangential and normal grinding forces, thus reducing the force on the individual abrasive particles. Therefore, the wear of the grinding tool is reduced, and the grinding heat can be reduced. However, the increase in the speed of the grinding tool reduces the maximum depth of cut of the abrasive grains, reduces the cross-sectional area of ​​the chips, and increases the number of cuttings and the heat of grinding. Both of these factors increase the amount of clogging [1]. According to the process requirements, the line speed of the grinding tool should reach 3000 rpm or more, and the machine speed should reach 6000 rpm. In order to prevent the machine vibration from adversely affecting, we generally choose 4000 rpm. At this time, the linear velocity of the edge of the abrasive tool is v=πdn. d is the diameter of the grinding tool and n is the speed of the machine tool. We choose d = 200mm, calculated v = 41.9mps, in line with the speed requirements of the processing technology.
2 thickness selection of the grinding tool base
The total thickness of the abrasive tool is 2 mm. Considering the thickness of the plating layer and the bottom nickel, the designed substrate thickness δ=2-2d1-2d2. D1 is the electroplated abrasive particle size and d2 is the bottom nickel thickness. Generally, the thickness of the base nickel is 3 to 5 μm, which is 4 μm. The choice of abrasive grain size primarily considers the requirements for grinding efficiency and surface roughness of the workpiece. Combining the two factors, we choose CBN with 100~120 grain size. According to GB6408-98 standard, the corresponding size is 120~150μm, the maximum value is 150μm, and the thickness δ=1.692mm is calculated. However, considering the thermal expansion of the sand, the thermal expansion according to experience is about 5 μm, so the final thickness is set to δ = 1.687 mm.
3Building and finite element analysis of the base of the grinding tool
1) Element model of abrasive tool modeling and abrasive meshing
2) Perform a finite element analysis to see the 3rd order natural frequency.
**INDEXOFDATASETS
ONRESULTSFILE**SETTIME/FREQLOADSTEPSUBSTEPCUMULATIVE
12477.2111
27661.8122
37696.3133
(3) Deformation of the natural frequency of each order. When the grinding tool is critically rotated, the base of the grinding tool is subjected to the greatest stress and the strain is the largest. When the "critical" state is reached, the grinding tool vibrates strongly, resulting in a decrease in the life of the grinding tool and even damage to the grinding tool [2]. The relationship between the critical speed of the grinding tool and the frequency is: n=60×f. n is the rotational speed (rpm) and f is the frequency (Hz). The grinding frequency can be converted to a critical speed, see Table 1. The working speed of the grinding tool is 4000 rpm. It can be seen from Table (1) that the working speed of the grinding tool is much lower than the critical speed.
At these frequencies, the grinding tool has a small amount of deformation and does not cause the grinding tool to be damaged during operation and can work normally.
4 conclusion
Under the condition of ensuring the manufacturing process of the abrasive tool, the abrasive tool according to the above design has less damage to the machine tool, the life of the grinding tool is high, and the processing precision can be ensured.
introduction