1 Bearing Introduction
The bearing shell is a sliding bearing used for the crankshaft journal and the like in the engine. The bearing is composed of a bimetal strip with a steel belt as a substrate and a layer of bearing alloy attached to the surface, and is manufactured through a series of processes. There are usually three types of bearing alloys in this layer: babbitt, aluminum tin alloy and copper lead alloy. This machine is an inner circle finishing boring machine designed and manufactured for Shaoxing Textile Machinery Factory and used for processing EQ140-1 spindle flanged tile (Figure 1). The bearing alloy of this spindle flange is aluminum-tin alloy, and the part that is cut by the broaching machine is the bearing alloy layer part.
Figure 1 EQ140-1 spindle flanged tile
2 Axial Bearing Inner Circle Finishing Process and Features
There are two main methods for precision machining of bearing bushes. One is boring machining and the other is broaching. The respective characteristics are shown in Table 1.
Table 1
Machining method boring broaching thickness accuracy(mm) Domestic 0.006 0.01 Foreign 0.004 0.006 Surface Roughness Ra
(μm) Domestic 0.4 0.4 Foreign 0.2 0.1 Productivity
(pieces/hour) Domestic 300 500 Overseas 400 1200
3 The current state of the internal bearing boring machine in China
At present, the general condition of the internal bearing boring machine in the country is:
The fixture adopts a gantry structure, but its rigidity is not strong, and the adjustment is inconvenient. The broach special sliding table adopts a traditional sliding guide rail, the guide rail has a large gap, the linear motion accuracy of the slide table is poor (0.016/1000), and the frictional resistance is large, resulting in the drive cylinder The heat is large, and the stability of the machine's precision is not good. Normally, it needs to be adjusted 2 or 3 times a day. In addition, the cutting and chip evacuation of the machine tool are manual operations, and the labor intensity is high, and the production efficiency is not high. In order to improve the accuracy and output of product parts, we have redesigned the broaching machine to solve the problems of poor accuracy, low productivity and poor stability.
4 Overall layout of the machine
The machine adopts horizontal layout (refer to the horizontal layout of the slide table, see Fig. 2). It is composed of clamps, pulling tires, sliding tables, broaches, feeding devices, feeding devices, electrical and hydraulic components, and its processing is : Put the part into the material collection slot of the feeding device. The slide will start from the B point to the left and go to point A. It will automatically take one piece of material from the collecting trough, then the right line will return to the B point and take the material to C at the same time. Point; ejector in the C point to the top of the material into the pull of the tire, the clamping device in the fixture will clamp the part, ejector back; slide left again, driving the broach pull the workpiece to point A; At the same time, at the point C, the material that has just been pulled is unloaded; the blanking device pulls the pulled part with the right line of the slide and pushes it into the material chute of the material feeding device; Take it out manually. In this way, a motion cycle is completed. All actions of the cycle are automatically performed under the control of the PLC.
Figure 2 Overall layout of the machine
1. Bed 2. Feeding device 3. Fixture 4. Broach 5. Cutting device 6. Feeding slot 7. Cylinder 8. Control panel 9. Hydraulic station
5 Main parts and technical requirements of machine tools
The fixture of the machine tool adopts a gantry structure (see Fig. 3), which has the function of supporting the pulling of the tire and clamping the workpiece. Since the jig is subject to full broaching force, it must have sufficient rigidity to withstand about 20,000 N impact force during broaching.
Figure 3 Fixture
1. Fine-adjusting the nut 2. Clamping the cylinder 3. Clamping the concrete 4, 6, 10. Tie rod 5. Chute slider 7. Balance lever 8, 9. Fine-tuning ramp 11. Pressure plate 12, 21. Pull the tire 13. Tool 14 Slide 15. Spindle 16. Revolver 17. Bumper cylinder 18. Draw lever 19. Stopper 20. Draw slider
The clamping mechanism is a key part of the fixture. First, it is required not to affect the broaching process during clamping. Since the clamping point of the bearing pad is on the steel back of the opposite side of the bearing pad, the thickness of the steel back is 2.15 mm, and the maximum clamping pressure width is 2 mm, so the press plate is used for each action. The location must be accurate so as not to press the knife more, and less pressure and pressure. Therefore, the pressure plate should set the positioning step. When relieving, the platen must be fully retracted so as not to touch the part when the material is removed. Second, the clamping force should be appropriate. Generally, the clamp pressure is 150% of the force applied when the bearing height is detected. The machine is 11000N, which is more appropriate. If the clamping force is too large, it will leave a mark of clamping pressure on the clamping point of the bearing bush; if the clamping force is too small, the fitting ratio of the positioning surface of the bearing pad and the positioning surface of the pulling tire will not reach more than 80%, which will affect the pull. Sharpness stability. Third, the clamp pressure on the two facing surfaces of the bearing bush should be equal, otherwise the bearing bush will rotate within the pulling tyre. The machine adopts a symmetrical pull rod force applying mechanism, which can make the clamp pressure on both sides equal. Fourth, the clamp should be self-locking so as not to cause fluctuations in the oil pressure and affect the stability of the product's accuracy when a large number of oil cylinders are involved in broaching. The machine adopts inclined self-locking device, the self-locking angle is 13° (see Figure 3), and it can be reliably locked.
Pulling the tire is a high-precision part, and the clamp needs to have a higher precision for pulling the bearing surface. However, since the curve of the arc surface of the tire after installation is difficult to be concentric with the axis of the round broach, the pulling of the tire on the fixture should be adjusted slightly from top to bottom, as shown in FIG. 3 . The machine adopts 1:100 slope adjustment, convenient and reliable, and good accuracy retention.
Because the bearing shell is a flexible part, when the clamping pressure plate is released, the part will not fall off by itself, so it needs to be struck on the steel back. In order not to injure the parts, the blanking lever in the material device (see Fig. 3) intentionally cuts off part of it to form a weak gap to increase the elasticity and cushion the striking force so as to avoid injuring the parts without affecting the beat of the processing. .
Sliding table (see Figure 4) is a dynamic part that drives the broach to cut, and its quality directly affects the machining accuracy of the part. The slide table of this machine tool is a hydraulic drive slide table. The slide table must have high linear motion accuracy, large thrust force (the thrust of the machine's cylinder is 35000N) and high movement speed. This not only improves efficiency, but also improves the surface roughness of the part and reduces cutting resistance. The slider's broaching speed is 20m/min and the return speed is 34m/min. The old sliding guide rail is difficult to meet these requirements. Therefore, the machine adopts a clearance-free rolling guide, six sliders (three sliders per guide, see Fig. 4) are selected, and rigidity of the saddle is improved. And carrying capacity. Since the rolling guide has a high linear motion accuracy (0.008/1000) and a small rolling friction coefficient (0.005), it can also pre-tighten the guide rail to form a backlash-free rolling, thus ensuring a greater load resistance of the slide table. Under the smooth linear motion, not only less heat, but also very easy to repair and replace.
Figure 4 slide
1. Slider 2. Saddle 3. Cylinder 4. Pressure plate 5. Pressure block 6. Cylinder bearing 7. Guide rail 8. Bed
The slide cylinder is also a key component. Due to the high speed of the slide, the cylinder must have good cushioning to reduce the impact. This cylinder adopts front and rear cover adjustable buffer device, see Figure 5. After the cover is taken as an example, the principle is: When the member 4 enters the member 3, the triangular groove starts to throttle, and the A cavity oil enters the B cavity through the triangular groove; when the triangular groove is closed, the A cavity oil enters the B through the adjustable flow cone valve The cavity forms a smaller throttling than the triangular groove and forms a buffer. The buffer effect produced by this type of structure is ideal, and even if the machine tool stops after high-speed operation, there is no impact phenomenon.
Figure 5 buffer device
1. Piston 2. Cylinder bore 3. Throttle ring 4. Damper sleeve 5. Throttle cone valve 6. Oil port 7. Retainer 8. Rear cover 9. Piston rod 10. Steel ball 11. Spring 12. Triangular groove
The quality of the tool is closely related to the quality of the part. The broach of this machine tool consists of 9 circular blades with a mandrel through the locking (see Figure 6), the first to the fourth piece is a rough cutting blade, each tooth volume is 0.1mm, 5th to 8th For teeth and proofreading teeth, the amount of tooth lift is shown in Table 2. The 9th piece is eccentrically mounted (the back of the mandrel has a 2mm step down) and is used to cut oil grooves on both sides of the bearing. The entire broach is held by the knife holder on the sliding saddle, and each blade can rotate when released. When the blade is worn, rotate the blade 180° to continue using it. In addition, it is better to grind the broach before use, so that the accuracy of the pull out of the bearing is stable, the broaching surface is bright as a mirror, the roughness up to Ra0.1μm; otherwise there is a trace on the surface of the part that is pulled out.
Figure 6 Broaches
1. Lock nut 2. 4. Spacer 3. Blade 5. Spindle
Table 2
Teeth number 4～5 5～6 6～7 7～8 Tooth volume (mm) 0.08 0.06 0.04 0.04The automatic loading and unloading device has a very large effect on the stable and reliable operation of the machine at high speed. The feeding device consists of a collecting trough and a spacer (see Figure 7). The collecting trough can vertically set 15 bearing bushes. When feeding, the spacer separates the upper material from the lowermost one, so as not to take two pieces at the same time during automatic feeding. The blanking device is composed of a slider-type jointer and a material chute (see Fig. 8). Their actions are accomplished by colliding with each other when the slide moves left and right. The action is: When the left side of the sliding table reaches point A, the impacting spacer moves to the left—separation of material. At this time, the bottom sheet of material falls on the ejector on the slide table (waiting for the ejector to follow the slide table. Return to point C, the top of the material into the pull the tire), at the same time at the C point has been processed bearing bushes, it was hit to the material slide chute on the slide; right slide, spacer in the spring Under the effect of the right move - discharge, to B, when the blank slider hit the bed fixed in the bed of the material, the material is automatically moved to the collection slot, after the full (15) was Workers take away. In this way, a loading and unloading cycle is completed. The loading and unloading device has a simple and reliable structure and is very convenient to use.
Figure 7 Feeding device
1.Retainer plate 2. Collection trough 3. Spring 4. Partition plate 5. Nut 6. Top material port 7. Impact block 8. Slide table 9. Bracket
Figure 8 Cutting device
1. Slide 2. Pusher 3. Slide 4. Slider 5. Tension spring 6. Sink 7. Holder
6 Conclusion
This machine has been used by users for several years and shows that it can run normally and automatically, with few faults and stable accuracy. The stability accuracy is: wall thickness tolerance is 0.007mm, surface roughness is Ra 0.1μm, productivity is 650 sheets/hour. This machine only needs to replace the pulling tire components, broach (with the same diameter does not change) and adjust the aggregate tank, it can adapt to different types, different specifications, different materials, the processing of the bearing, the inadequacy of the chip is not ideal.
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