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Journal of Mechanical Engineering Science and Technology (JMEST)

Abstract

The durability of Bonnell springs, which are widely used in the manufacture of spring beds, is often compromised by height reduction during use, which negatively impacts product comfort and quality. This study aims to minimize spring height reduction by investigating the effects of heating temperature and carbon content in the spring steel. A full factorial experimental design was applied using two factors: heating temperature (250°C, 260°C, and 270°C) and carbon content (0.72%, 0.73%, and 0.74%). Nine treatment combinations were tested, with five replicates each, and the height reduction values were measured after 100 compression cycles. The data were analyzed using Analysis of Variance and HSD post-hoc test to evaluate the significance of the main effects and treatment differences. The finding indicated that heating temperature and carbon content had a significant effect on spring height reduction, while the interaction between the two was not statistically significant. Increasing carbon content from 0.72% to 0.74% reduced height reduction, and higher heating temperatures, particularly 270°C, also contributed to lowering the height reduction. The combination of 270°C and 0.74% C resulted in the smallest average height reduction of 0.62 cm, below the company's maximum tolerance of 1 cm. However, operational challenges with the spring coiling machine and reduced comfort limited its adoption. As an alternative, the combination of 260°C – 0.73% C was identified, resulting in a height reduction of 0.92 cm, well within the company’s specification and reducing the defect rate. These findings provide practical guidance for optimizing manufacturing parameters to improve the spring bed quality.

Publisher

State University of Malang (UM)

First Page

359

Last Page

552

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