RESUMO
Roundness is one of the most important evaluation indexes of rotary parts. The formation and change of roundness in the machining of parts is essentially the formation and genetic process of profile. Centerless positioning machining is one of the main surface finishing methods of rotary parts. The rounding mechanism of centerless positioning machining determines its unique roundness profile formation and genetic characteristics. How to eliminate the roundness error of centerless positioning machining has become one of the important issues in the research of high-precision rotary part machining. This paper explores the influence of process parameters on the roundness error from the perspective of profile evolution during centerless grinding and electrochemical mechanical machining, with the aim of providing a cross-process collaboration strategy for improving bearing raceway accuracy. Through an experiment of centerless grinding, the influence law and mechanism of process parameters on the profile are discussed. On this basis, electrochemical mechanical machining experiments are designed to explore the variation rules and mechanisms of different profile shapes in the machining process. The cross-process collaboration strategy is studied, and reasonable parameters of centerless grinding and electrochemical mechanical machining are determined. The results show that in the centerless grinding stage, increasing the support plate angle can form a multiple-lobe profile with high frequency within a wide range of process parameters. Electrochemical mechanical machining can effectively smooth the high-frequency profile and appropriately expanding the cathode coverage can improve the roundness error and reduce the requirement of initial accuracy of a multiple-lobe profile workpiece to a certain extent. Therefore, the combined machining technology of "centerless grinding + electrochemical mechanical machining" provides an efficient technical means to realize the precision machining of rotary parts such as bearing raceways.
RESUMO
Background and Aim: A technique of endoscopic tightening of the cardia mucosa for the treatment of gastroesophageal reflux disease (GERD) was developed and its clinical efficacy was observed. Methods: 120 patients with GERD who underwent endoscopic tightening surgery from December 2017 to December 2019 were included in this study. GERD-Q score and constitution type of patients were evaluated preoperatively and at 1 month, 3 months, 6 months, and 1 year after surgery. In addition, effectiveness and side effects of the procedure were graded based on gastroesophageal flap valve (GEFV) function. Results: GERD-Q score of 1 month, 3 months, 6 months, and 1 year after surgery were significantly decreased (P<0.01) compared with preoperative score. There were no significant differences between GERD-Q score of 1 month, 3 months, 6 months, and 1 year after surgery. The surgery proves to be effective in all GEFV grades, especially in Hill-III. Conclusion: Endoscopic tightening is an effective method for the treatment of patients with GERD, especially of Hill-III patients. Attention should be paid to cardia width, ligation ring depth, and ring number during operation. Relevance for Patients: ETCM is a safe endoscopic procedure with minimal trauma, which has been proved effective for patients who are diagnosed with GERD.
RESUMO
Background and Aim: A technique of endoscopic tightening of the cardia mucosa for the treatment of gastroesophageal reflux disease (GERD) was developed and its clinical efficacy was observed. Methods: 120 patients with GERD who underwent endoscopic tightening surgery from December 2017 to December 2019 were included in this study. GERD-Q score and constitution type of patients were evaluated preoperatively and at 1 month, 3 months, 6 months, and 1 year after surgery. In addition, effectiveness and side effects of the procedure were graded based on gastroesophageal flap valve (GEFV) function. Results: GERD-Q score of 1 month, 3 months, 6 months, and 1 year after surgery were significantly decreased (P<0.01) compared with preoperative score. There were no significant differences between GERD-Q score of 1 month, 3 months, 6 months, and 1 year after surgery. The surgery proves to be effective in all GEFV grades, especially in Hill-III. Conclusion: Endoscopic tightening is an effective method for the treatment of patients with GERD, especially of Hill-III patients. Attention should be paid to cardia width, ligation ring depth, and ring number during operation. Relevance for Patients: ETCM is a safe endoscopic procedure with minimal trauma, which has been proved effective for patients who are diagnosed with GERD.