1 main problem The point is made of forged blank, the material is 40Cr. The main process is: rough forging - rough axle end - rough milling (planar and two cranks) - heat treatment (tempering) - finishing two spindle ends - finishing milling crank - car Qu Chu - car oil pump eccentric - drilling - crank turn high frequency quenching - car oil pump eccentric - grinding spindle - grinding turn - milling keyway. However, some problems were found in the processing: the oil pump journal, the eccentricity, the grinding spindle, and the cranking tool are complicated, and the machining accuracy is not high; the surface hardness of the two cranks is low; the crank is easy to break; During the user's use, the connecting rod was found to be dead, and finally the crankshaft was found to be cracked at the inclined oil hole at the crank. 2 problem analysis and process improvement (1) Since the lubrication of the V2. 4 air compressor crankshaft is mainly through a plunger pump installed at the end of the crankshaft, and the plunger pump works by the rotation of the crankshaft to perform the crankshaft and the connecting rod and the connecting rod mounted on the crankshaft. Lubrication, so the crankshaft is designed to be eccentric at the end, but when starting the production process, I only want to use the tooling to ensure the machining accuracy of the parts. However, during the machining process, it is found that the center of the two ends is not on the same line, so the car turns, In some processes of eccentricity and grinding, molds must be designed and manufactured. Because they are different fixtures, during the installation process, the center will definitely be biased in consideration of the installation error. Therefore, it is decided to increase the length to 40 at the eccentricity and the outer diameter is 50 pieces of processing technology, so that it can be well ensured that the processing steps can be installed and processed in the same center hole, which not only can reduce the number of fixtures in the process, but also the dimensional accuracy of the parts. Can be well guaranteed. (2) The crank is a key part of the crankshaft movement, and the piston is driven by a connecting rod connected to the crank to compress the air. Therefore, the crank has to be strong enough to have sufficient strength and wear resistance. Therefore, the high-frequency quenching of the crank and the oil pump journal is arranged in the process, and the hardness value is required to be HRC45-50. However, after processing, the hardness value is lower than the design requirement, and then the crankshaft just heat-treated is measured. It was found that the hardness value was basically between 45 and 48, which met the design requirements. The reason for chasing the original is that the machining allowance is too large before the high-frequency quenching of the crank and the pump journal in the design process, resulting in the hardness value of the parts after grinding. Under the premise of not changing the heat treatment process, it is also necessary to ensure sufficient toughness of the core at the crankshaft of the crankshaft. Therefore, the rough grinding process is added before the high frequency quenching. That is, the rough grinding turns to 50. 4 0. 03, puts the finishing allowance of 0.4, after the processing according to this process, the hardness of the parts meets the design requirements. (3) After the user uses the crankshaft fittings provided by our factory at the beginning stage, the magnetic powder is detected on the crankshaft after one year of operation, and it is found that cracks appear at different points in the crank joint, which seriously affects the service life of the product. Security risks. Our company analyzes the problems raised by the customers layer by layer and finds that the excessive rounding of the crank can be too small, because during the crankshaft movement, the stress concentration phenomenon is most likely to occur here, and the information from the customer feedback is also the same. Where the cracks appear most, the reason is that the excessive rounding of the team's turn in the production process may be too small, according to the Machinery Industry Press? The reference formula provided by the piston compression design is r=(0. 05 0. 06)D, D is the diameter of the crank, and the company adopts the overfilling method. However, in order to not excessively weaken the strength of the crank, the company considered the excessive rounding to be R1 (the original design value is 0.5). After the customer used it, it reflected well. (4) The oil hole on the crankshaft is generally in the form of a slanted oil hole or a right angle oil hole, depending on the shape of the crankshaft and the mode of oil supply. The diameter of the oil hole is about 0.05 to 0.06 times the diameter of the journal, but it should not be less than 3 mm. The oil hole should be rounded and polished at the intersection of the journal surface. The radius of the round hole is about half of the diameter of the oil hole to improve The fatigue strength of the crankshaft. Our company's V2. 4 crankshaft oil hole diameter is 5mm. After the hole is finished, except for the oil hole at the crank, the other oil hole ends are sealed with G1/8 screw and sealed. However, during the use of the customer, the connecting rod and the crankshaft are killed, and the magnetic powder is detected on the crankshaft after the joint. It is found that there are two or three cracks on the end face of the inclined oil hole at the crank, and the crack may be generated after the analysis. This phenomenon occurs when the connecting rod is brought into motion. Our company later found that after drilling the inclined hole, one end and the crank turn produced a thin edge, analyzed the possibility generated in each processing step, and re-examined the magnetic powder in the stocked product, and finally determined that it may be in the right After the high-frequency quenching of the crank, the crack caused by the extremely rapid cooling. In order to prevent the similar situation from happening again, the company took a series of measures, but the effect was very small. There were more or less cracks on the edge of the inclined hole. Finally, it is decided to insert a length of not less than 8 in several oil holes of the crank, and the copper rod with a hole interference of not less than 0.05 is knocked into the oil hole before the high frequency quenching, and the end surface is smoothed after being knocked in. The high frequency quenching of the crank is eliminated. According to this processing technology, the subsequent batches of the crankshaft were inspected and analyzed, and no similar situation occurred, and the problem was finally solved. 3 Conclusion After the modification of the above process, the company's recent V2. 4 air compressor crankshaft finished product qualification rate has been greatly improved, after the customer's use, it reflects very well. Cylinder Type Sewing Thread Bobbin Winding Machine Tube Thread Winder,Spool Reeling Machine,Spindle Spool Textile Machine,Metal Yarn Winding Machine Ningbo Yongfu Textile Machinery Co., Ltd. , https://www.yfwinders.com
Improvement and use of air compressor
There are two basic types of compressor crankshafts, the crankshaft and the crankshaft. The crankshaft structure, together with the motor shaft, generally has only two main bearings, which are less sensitive to bearing deflection and facilitate crankshaft mounting. However, the crankshaft compressor can only be used in a horizontal type, which makes the machine bulky and has a large foundation. The V2.4 air compressor made by our company adopts a curved shaft to arrange the connecting rod piston structure in a symmetrical manner, so that the compressor is compact and light in weight. However, there have been many problems in the early processing of the crankshaft. In order to solve these problems, we have taken a series of improvement measures.