Gear bore and gear shaft cylindrical, carburizing quenching, the hardness of 50 ~ 62HRC. The use of carburizing quenching heat treatment before the margin, carburizing quenching heat treatment after grinding to the pattern requirements of the process; carburizing quenching heat treatment before the margin, carburizing quenching heat treatment, with CBN blade turning to the pattern requirements method. Gear and gear shaft with the hole and the outer circle has a higher accuracy requirements, carburizing quenching heat treatment before the margin, carburizing quenching heat treatment after grinding method, the grinding process production costs are higher, the production cycle is long. Carburizing quenching heat treatment before the margin, carburizing quenching heat treatment with CBN blade turning method to work out the workpiece, the surface roughness, shape accuracy is not stable, not mass production, poor economy.
1. Grinding method analysis
In order to ensure the gear, gear shaft carburizing quenching heat treatment after the normal processing, carburizing quenching heat treatment before leaving the margin, to avoid carburizing quenching heat treatment deformation, so that the workpiece size tolerance,Gear Shaft can not be processed to the pattern requirements, especially the thinner gear , Relatively large diameter of the gear shaft generally stay 1 ~ 3mm margin. There are the following difficulties in grinding:
(1) grinding wheel easy to blunt, batch production often need to dress the wheel, grinding wheel after the need to re-knife to ensure that the processing size.
(2) workpiece carburizing quenching heat treatment deformation, need to repeat the knife, set the grinding starting point.
(3) grinding feed speed is limited, too fast, easy to cause the workpiece surface burns, resulting in cracks.
(4) the operator's skill level dependence, can not achieve semi-automatic production.
(5) long-term grinding of the gas mist,Gear Shaft the operator has a certain health effects.
Grinding is the more common processing technology, can guarantee the accuracy of parts processing, but the production efficiency is low, not environmentally friendly, product delivery time is long, in the market economy environment competitive advantage is not obvious.
2. Turning method analysis
CBN blade hardness is high, compared to the processing of low hardness of the material, the tool to be harder, more wear-resistant, greater strength. Cutting itself is a collision, friction and extrusion process, and produce a lot of heat, especially the tip part of the highest temperature
Directly with the CBN blade semi-fine car, fine processing,Gear Shaft the tip of the fillet can easily occur after the angle of wear, or even rounded corners and other adverse conditions (see Figure 2).
The workpiece surface due to tool nose angle wear, tool edge failure can not guarantee the processing accuracy. The surface of the workpiece will be worn due to the tip angle, cutting can not be chip, chip removal, chip breaking, leaving the surface roughness quality deterioration
Processing diameter of 100mm, length 86mm hole, can be processed 62, of which 6 surface roughness value Ra = 3.6 ~ 4.5μm, 11 precision tolerance. So with CBN blade turning, although it can achieve the purpose of hard cars, but the quality of instability, not mass production, play no economic benefits.
CBN turning technology on the lathe, processing high hard parts can be doubled to improve efficiency, but by the current domestic tool manufacturing level restrictions,Gear Shaft the blade CBN components subject to a special process smelting, the current domestic can only provide cutting 50HRC the following price is better Of the CBN blade, 50HRC above the need to import, import SUMITOMO, Sandvik, KENNA and other companies blade, the domestic can provide the overall CBN blade, the use of good results.
3. Improved efficient hard drive technology
Improved hard car technology using semi-fine car and finishing two processes processing parts to the pattern requirements.
From the inspection records and production statistics, the use of ceramic blade semi-fine cars, CBN blade fine car parameters shown in Table 3.
Semi-fine car with a ceramic blade for hard car, a single margin of 0.1 ~ 0.2mm. Ceramic blade hardness inferior to CBN, but higher than carbide, the surface of the chemical coating with CVD, with high wear resistance, and the blade price at least 5 times lower than the CBN for semi-fine car to remove carburizing after heat treatment surface residual Oxide, carburized hardened layer, can get a good price.
Train used CBN blade hard car. CBN blade to be used with a back angle blade, the general 7 ° can be used with the angle of the former angle of the arbor, because the surface roughness value Ra should be less than 1.6μm, the tip angle should be used more than 0.4mm, cutting each Transfer should be controlled at 0.04 ~ 0.08mm / r, the line speed should be controlled at 60 ~ 80m / min, cutting depth should be controlled at 0.1 ~ 0.2mm. In order to ensure that the fine car is a knife that is required, the test should be a short distance to confirm the accuracy, the fine car to the pattern requirements. Fine car when the high pressure cutting fluid, the better.
A single edge processing diameter of 100mm, length 86mm hole, can be processed 151 pieces, of which 151 surface roughness value Ra = 1.0 ~ 1.6μm, no parts of the accuracy of tolerance. The production efficiency is increased by 68% to 75% compared with grinding, and the processing cost per unit is about 48%. Compared with CBN, the finishing cost is 38% ~ 50%, the processing cost is about 52.5% Quality and stability, to meet the mass production requirements.