"We must complete the polishing of the piston rod on February 27, and we must not affect the normal development of the final assembly work in the later stage." The leader of the CNC machining branch of Jiangnan Industrial Group said at the work meeting when arranging the production of the new batch of seat cushions.
All chrome-plated surface treatment parts must be polished before proceeding to the next final assembly work. In the whole production process, the most difficult thing is the polishing of the piston rod. The piston rod is the core part of the seat buffer, and it is necessary to do a cooperative sliding between the seal guide barrel and the upper lock assembly, which requires very high surface roughness. Drawings require roughness to reach Ra0.8 or above, but according to the company's previous production experience, the internal control requires roughness to reach Ra0.2 or more.
After receiving the polishing task on February 14, the CNC machining branch factory handed it over to Fu Jian, the second shift leader of the fourth workshop who specialized in gnawing "hard bones", to be responsible for completing it. He polished the outer diameter of the piston rod according to the previous method, first using water sandpaper for preliminary grinding, and then using wool felt for precision grinding, and the roughness only reached Ra0.6. He Peng, the person in charge of the final assembly of the seat buffer who assisted in the production and the quality officer of the fitter class in the first workshop, proposed that the 240# sandpaper should be sanded three times before polishing, and then the conventional polishing operation should be carried out. This removes peaks from the outer surface of the product, resulting in better results when grinding. This method increases the surface roughness to Ra0.4.
The polishing of the outer surface could not be attacked for a long time, and Fujian reported the problem to the branch workshop. The branch arranged Liu Hong, director of the technical quality room, and Cao Yuxiang, a quality inspector, to cooperate with the research. Liu Hong analyzed that diamond cotton is more delicate than sandpaper and rougher than water sandpaper. He suggested adding a work step after sandpaper sanding and before sanding water sandpaper, using diamond cotton to polish three times to remove the second layer of peaks on the surface. Cao Yuxiang analyzed after inspecting the polishing process, the wool felt is very delicate, as the last step of fine polishing, if the polishing time is not enough, the polishing amount must be very limited. He suggested increasing the polishing time of wool felt from 1 hour to 2 hours to increase the polishing volume of fine polishing. The above two supplementary improvement schemes were implemented together, and the roughness finally reached Ra0.2.
After finishing the research on the outer surface, Fujian began to polish the inner hole. The bottom depth of the inner hole is finger-long, and if the finger is pressed against the wool felt for grinding, there is a safety risk, and the roughness of the bottom of the inner hole cannot be guaranteed. He thought of a way to make a nylon stick to grind the inner hole by pressing the wool felt instead of his fingers. He clamped the piston rod to the lathe's three-prong and turned the spindle to rotate. At this time, the nylon rod could not hold the wool felt, and after a while the wool felt ran away in the direction of the rotation of the main axis. He tackled the problem again, glued the back of the wool felt with 502 glue, and pasted it on the nylon rod for internal hole polishing, which completely solved the problem of the alienation of the wool felt and ensured that the bottom of the inner hole was polished in place.
Then, through the joint efforts of the seat buffer project team members, the polishing problems such as low grinding efficiency and ring patterns on the surface were overcome in time. Fujian catches up with the production progress by working overtime to ensure the timely completion of the piston rod polishing work. (Correspondent Xu Xianghan)