초정밀 가공 방법중 하나인 자기연마 가공법을 사용하여 자동차용 인젝터 노즐의 초정밀 가공을 연구하고 자기연마의 가공후 수치 변동이 거의 없다는 장점을 이용하여 사용하여 고장판정 받은 인젝터 노즐의 니들을 자기연마 가공하여 인젝터의 재사용 가능여부를 실험하기 위하여 인젝터 성능실험한 결과 인젝터 성능실험 기준치에 모두 합격하는 좋은 결과를 얻을수 있었고 인젝터 노즐을 초정밀 가공 할 수 있었다....
초정밀 가공 방법중 하나인 자기연마 가공법을 사용하여 자동차용 인젝터 노즐의 초정밀 가공을 연구하고 자기연마의 가공후 수치 변동이 거의 없다는 장점을 이용하여 사용하여 고장판정 받은 인젝터 노즐의 니들을 자기연마 가공하여 인젝터의 재사용 가능여부를 실험하기 위하여 인젝터 성능실험한 결과 인젝터 성능실험 기준치에 모두 합격하는 좋은 결과를 얻을수 있었고 인젝터 노즐을 초정밀 가공 할 수 있었다.
초정밀 가공 방법중 하나인 자기연마 가공법을 사용하여 자동차용 인젝터 노즐의 초정밀 가공을 연구하고 자기연마의 가공후 수치 변동이 거의 없다는 장점을 이용하여 사용하여 고장판정 받은 인젝터 노즐의 니들을 자기연마 가공하여 인젝터의 재사용 가능여부를 실험하기 위하여 인젝터 성능실험한 결과 인젝터 성능실험 기준치에 모두 합격하는 좋은 결과를 얻을수 있었고 인젝터 노즐을 초정밀 가공 할 수 있었다.
Amidst growing demands for higher precision parts by each industrial segment abreast with the advancement of industrial technologies, researches on technological methodologies focused on deburring or mirror finishing have been intensely made. Among them is magnetic abrasive finishing or polishing (M...
Amidst growing demands for higher precision parts by each industrial segment abreast with the advancement of industrial technologies, researches on technological methodologies focused on deburring or mirror finishing have been intensely made. Among them is magnetic abrasive finishing or polishing (MAF), that is, an environment-friendly method providing highly polished surfaces with ease such as inner or outer surfaces of pipe. The MAF process has evolved along with wide spectrum of researches on e.g. improvement of surface precision involving such difficult-to-cut materials as aluminum, ceramic and titanium as well as high efficiency in machining of molded surfaces, removal of micro-burrs in precision parts, etc. Taking advantage of MAF allowable for little change in terms of dimension of workpiece after grinding, this study pursues higher level of precision as for automobile parts by experimentally performing ultra-precision machining of needles in an injector nozzle used as car part, and explores the possibility of reusing those needles having been judged as defective if they are MAF processed. More specifically, needles of injector nozzle judged as no-more-usable were selected as specimens for MAF, and measured in terms of Ra and Rz of surface roughness at the time of pre- and post-MAF based on the preset test design. They were further measured for roundness and comparatively analyzed one by one. Meanwhile, new (not used) needles were measured with respect to Ra and Rz of surface roughness and roundness, whereby values measured were deemed as experimental references. Next, MAFs applied to as-defective ones were carried out and their surface hardness subject to abrasive was observed in an attempt to obtain Ra/Rz values better than the above references and improve roundness. Diamond was used as abrasive. Observations were made as per the polishing characteristics of diamond depending on size thereof and the MAF characteristics of specimens depending on size of iron base particles. By way of investigating the polishing characteristics of specimens depending on sizes of diamond abrasive and iron base particle, the sizes exhibiting the best result were determined. Diamond and iron base particles having such sizes were mixed to make an abrasive, which was used to observe the status of surface polished subject to the number of rotation of the specimen with an aim to finding the optimal polishing condition. According to the result of rotation speed that led to the best polishing, the characteristics of magnetic abrasive polishing for specimens were observed under the wet and dry abrasive condition. In the case of MAF using 1.0 um size of diamond abrasive, Ra value was the best when polishing was made for 25 sec by showing 0.015 um, while as for 0.5 um sized diamond abrasive Ra was 0.02 um exhibiting specific change. In the case of MAF using 1.0 um size of diamond abrasive, Rz value was the best by showing 0.1 um when polishing was made for 5 sec, 25 sec and 30 sec, respectively. Although slightly irregular change was found in all abrasives, the value of roundness was best obtainable by showing 0.15 um when polishing was made for 15 sec with the use of 0.5 um diamond abrasive. As for 0.5 um size of diamond abrasive, values in terms of surface roughness were regularly varied when viewed from the result of post-polishing specimens. Change in diameter was also accomplished within permissible error in regard of injector as automobile part and roundness values were agreeably acceptable. In the experiment aimed to observe the MAF characteristics by size of 0.5 um abrasive and iron base particles, it was found that 800-mesh size of iron base particles showed irregular variation in terms of both Ra and Rz of surface roughness. What was worse was that such irregularity was detected in terms of roundness, which demonstrated that #800 could not be good abrasive in view of MAF. On the other hand, in case where MAF was performed by using the mixture of 0.5 um diamond abrasive and #500 iron base particles, surface roughness, Ra, was improved to be up to 0.02 um with stable change, while surface roughness, Rz, also exhibited stable change. As to roundness, 15-second application resulted in 0.15 um, which was the best in testing for magnetic polishing characteristics by size of iron base particles. For testing targeted on #320 iron base particles, Ra showed comparatively stable change, but Rz generated irregular change, while roundness tended to be up to 0.21 um when polished for 15 sec. In an experiment using #200 iron base particles, Rz was the best with 0.015 um over experiments by size of iron base particles. Rz also showed not-so-bad result with achievability up to be 0.1 um. As for roundness, good result was obtainable to the extent of being 0.19 um when polished for 30 sec. The finding via this study to investigate the optimized composition of abrasive fit to MAF in connection with reuse of injector was that mixing of 0.5 um size of diamond and 200 mesh of iron base particles lead to the best result. In tests attempting to analyze magnetic polishing characteristics depending on rotating speed of specimens based on mixture of 0.5 um diamond abrasive and #200 iron base particles, not so much improvement was made due to irregularly changing Ra and Rz values with increasing rotation speed of specimens. Roundness of specimens was also the same case. Changes in weight and diameter of specimens after the application of MAF were greatly changeable with the faster the rotation of specimens. The reason why surface roughness failed to be better with increasing rotating speed of specimens was that abrasive particles tended to be dispersed around a magnet due to centrifugal force arising from specimen’s rotation. Under the condition like that, it could be said that, to induce noticeable improvement in terms of surface roughness and roundness of specimens sampled for this study, MAF be processed with low rotation speed of 1,000 rpm. With regards to tests for observing MAF characteristics under both wet polishing and dry polishing conditions with the use of abrasive specimens made by drying diamond for seven days, and mixing 0.5 um diamond abrasive and #200 iron base particles, the case of MAF in a wet state in which 0.07 ml of light oil was added showed better result in terms of Ra and Rz rather than the case of dry state to which no light oil was added and the case where diamond abrasive was dried for 7 days so as to make dried the oily content of the abrasive. Improvement of roundness of specimens was the best in the case of MAF under the dry state without addition of light oil. As to changes in diameter and weight of specimens, they were the biggest in a wet state with 0.07 ml of light oil added. For tests of MAFs according to the magnetic polished status of specimens, the case of MAF under the wet condition showed the best improvement involving roundness only, having no betterment in terms of surface roughness. The performance test with respect to injector nozzle was carried out in such a way that abrasive in this regard was prepared by mixing 0.5 um diamond abrasive and #200 iron base particles and specimens being rotated with 1000 rpm were magnetic-polished for 15 sec in a wet state. This test was made under the support by a company named, “Jeonjoo Common Rail” focused on 3 factors such as idle injection, main injection and returning quantity by using injector testing instrumentation. Specimens used hereof were those obtained by applying MAFs against 4 needles of injector nozzle which had been determined defective. As a result, all of those 3 performance factors were improved with significance. The conclusions of this study on analysis of MAF characteristics of adopted specimens are as follows; the MAF processing condition, i.e. use of 0.5 um diamond mixed with #200 iron base particles and 15-sec long application of MAF in a wet state with 1,000 rpm, leads to the results of 0.015 um of surface roughness, Ra, and 0.1 um of surface roughness, Rz, 0.22 um of roundness and 0.31 um of diameter change rate, all the values of which address that such MAF processing condition bears better result than even newly machined product. These experimental conclusions were verified by testing needles of injector nozzle that had been judged as defective for automobile parts through MAFs, resulting in good scores in all experimental factors. In addition to the authentication backed up by preceding researches that the MAF process is contributed to longer life span of workpieces, this study surely reconfirms that ultra-precision machining of needles relying on MAF will greatly prolong use life of those parts.
Amidst growing demands for higher precision parts by each industrial segment abreast with the advancement of industrial technologies, researches on technological methodologies focused on deburring or mirror finishing have been intensely made. Among them is magnetic abrasive finishing or polishing (MAF), that is, an environment-friendly method providing highly polished surfaces with ease such as inner or outer surfaces of pipe. The MAF process has evolved along with wide spectrum of researches on e.g. improvement of surface precision involving such difficult-to-cut materials as aluminum, ceramic and titanium as well as high efficiency in machining of molded surfaces, removal of micro-burrs in precision parts, etc. Taking advantage of MAF allowable for little change in terms of dimension of workpiece after grinding, this study pursues higher level of precision as for automobile parts by experimentally performing ultra-precision machining of needles in an injector nozzle used as car part, and explores the possibility of reusing those needles having been judged as defective if they are MAF processed. More specifically, needles of injector nozzle judged as no-more-usable were selected as specimens for MAF, and measured in terms of Ra and Rz of surface roughness at the time of pre- and post-MAF based on the preset test design. They were further measured for roundness and comparatively analyzed one by one. Meanwhile, new (not used) needles were measured with respect to Ra and Rz of surface roughness and roundness, whereby values measured were deemed as experimental references. Next, MAFs applied to as-defective ones were carried out and their surface hardness subject to abrasive was observed in an attempt to obtain Ra/Rz values better than the above references and improve roundness. Diamond was used as abrasive. Observations were made as per the polishing characteristics of diamond depending on size thereof and the MAF characteristics of specimens depending on size of iron base particles. By way of investigating the polishing characteristics of specimens depending on sizes of diamond abrasive and iron base particle, the sizes exhibiting the best result were determined. Diamond and iron base particles having such sizes were mixed to make an abrasive, which was used to observe the status of surface polished subject to the number of rotation of the specimen with an aim to finding the optimal polishing condition. According to the result of rotation speed that led to the best polishing, the characteristics of magnetic abrasive polishing for specimens were observed under the wet and dry abrasive condition. In the case of MAF using 1.0 um size of diamond abrasive, Ra value was the best when polishing was made for 25 sec by showing 0.015 um, while as for 0.5 um sized diamond abrasive Ra was 0.02 um exhibiting specific change. In the case of MAF using 1.0 um size of diamond abrasive, Rz value was the best by showing 0.1 um when polishing was made for 5 sec, 25 sec and 30 sec, respectively. Although slightly irregular change was found in all abrasives, the value of roundness was best obtainable by showing 0.15 um when polishing was made for 15 sec with the use of 0.5 um diamond abrasive. As for 0.5 um size of diamond abrasive, values in terms of surface roughness were regularly varied when viewed from the result of post-polishing specimens. Change in diameter was also accomplished within permissible error in regard of injector as automobile part and roundness values were agreeably acceptable. In the experiment aimed to observe the MAF characteristics by size of 0.5 um abrasive and iron base particles, it was found that 800-mesh size of iron base particles showed irregular variation in terms of both Ra and Rz of surface roughness. What was worse was that such irregularity was detected in terms of roundness, which demonstrated that #800 could not be good abrasive in view of MAF. On the other hand, in case where MAF was performed by using the mixture of 0.5 um diamond abrasive and #500 iron base particles, surface roughness, Ra, was improved to be up to 0.02 um with stable change, while surface roughness, Rz, also exhibited stable change. As to roundness, 15-second application resulted in 0.15 um, which was the best in testing for magnetic polishing characteristics by size of iron base particles. For testing targeted on #320 iron base particles, Ra showed comparatively stable change, but Rz generated irregular change, while roundness tended to be up to 0.21 um when polished for 15 sec. In an experiment using #200 iron base particles, Rz was the best with 0.015 um over experiments by size of iron base particles. Rz also showed not-so-bad result with achievability up to be 0.1 um. As for roundness, good result was obtainable to the extent of being 0.19 um when polished for 30 sec. The finding via this study to investigate the optimized composition of abrasive fit to MAF in connection with reuse of injector was that mixing of 0.5 um size of diamond and 200 mesh of iron base particles lead to the best result. In tests attempting to analyze magnetic polishing characteristics depending on rotating speed of specimens based on mixture of 0.5 um diamond abrasive and #200 iron base particles, not so much improvement was made due to irregularly changing Ra and Rz values with increasing rotation speed of specimens. Roundness of specimens was also the same case. Changes in weight and diameter of specimens after the application of MAF were greatly changeable with the faster the rotation of specimens. The reason why surface roughness failed to be better with increasing rotating speed of specimens was that abrasive particles tended to be dispersed around a magnet due to centrifugal force arising from specimen’s rotation. Under the condition like that, it could be said that, to induce noticeable improvement in terms of surface roughness and roundness of specimens sampled for this study, MAF be processed with low rotation speed of 1,000 rpm. With regards to tests for observing MAF characteristics under both wet polishing and dry polishing conditions with the use of abrasive specimens made by drying diamond for seven days, and mixing 0.5 um diamond abrasive and #200 iron base particles, the case of MAF in a wet state in which 0.07 ml of light oil was added showed better result in terms of Ra and Rz rather than the case of dry state to which no light oil was added and the case where diamond abrasive was dried for 7 days so as to make dried the oily content of the abrasive. Improvement of roundness of specimens was the best in the case of MAF under the dry state without addition of light oil. As to changes in diameter and weight of specimens, they were the biggest in a wet state with 0.07 ml of light oil added. For tests of MAFs according to the magnetic polished status of specimens, the case of MAF under the wet condition showed the best improvement involving roundness only, having no betterment in terms of surface roughness. The performance test with respect to injector nozzle was carried out in such a way that abrasive in this regard was prepared by mixing 0.5 um diamond abrasive and #200 iron base particles and specimens being rotated with 1000 rpm were magnetic-polished for 15 sec in a wet state. This test was made under the support by a company named, “Jeonjoo Common Rail” focused on 3 factors such as idle injection, main injection and returning quantity by using injector testing instrumentation. Specimens used hereof were those obtained by applying MAFs against 4 needles of injector nozzle which had been determined defective. As a result, all of those 3 performance factors were improved with significance. The conclusions of this study on analysis of MAF characteristics of adopted specimens are as follows; the MAF processing condition, i.e. use of 0.5 um diamond mixed with #200 iron base particles and 15-sec long application of MAF in a wet state with 1,000 rpm, leads to the results of 0.015 um of surface roughness, Ra, and 0.1 um of surface roughness, Rz, 0.22 um of roundness and 0.31 um of diameter change rate, all the values of which address that such MAF processing condition bears better result than even newly machined product. These experimental conclusions were verified by testing needles of injector nozzle that had been judged as defective for automobile parts through MAFs, resulting in good scores in all experimental factors. In addition to the authentication backed up by preceding researches that the MAF process is contributed to longer life span of workpieces, this study surely reconfirms that ultra-precision machining of needles relying on MAF will greatly prolong use life of those parts.
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