การประยุกต์ใช้ชุดเทคนิควิศวกรรมย้อนรอยเพื่อปรับปรุงประสิทธิภาพของเฟืองยกของปั้นจั่นแบบหอสูง

Abstract

This research was studied to improve efficiency of a hoist gear set of a tower crane using reverse engineering technique. It was focused on the characteristics and properties of a hoist gear part, including dimension, composition, microstructure and hardness as well as hardening process. It was found that the original gear was made from low alloy steel with chromium and molybdenum addition or SCM 425 grade. Hardness at surface and at the base of teeth of the gear was 60 and 42 HRC, respectively. The hardness depth having 550 HV was about 0.7 mm. The microstructure at surface was martensite whereas the base of the teeth was bainite. Compared to the original part, gears produced by a local machining shop had smaller width and longer height of their teeth about 10%. SCM 440 grade steel, medium carbon steel, was used to manufacture the gear set due to a limitation of supply in Chiang Mai area. New gear set manufactured by gear hobbing process in this study had better accuracy in dimension, comparing to the damaged gear from the local shop. The hardness profile at the base of the teeth was improved by carrying out experiments on a cylinder and gear specimens with different heat treatment conditions. It was believed that the developed gears might have better efficiency, leading to longer life.