| Summary: | 碩士 === 國立中興大學 === 機械工程學系所 === 105 === Spindle is the key component of a machine tool thus requires high precision. In addition to the precision of the spindle, firm and accurate assembly also play important roles in its final precision. This study is aimed toinvestigating tolerance analysis and adjustment in the assembly of the spindle head system for a CNC lathe. A cost-tolerance model dedicated for this spindle is constructed. Sensitivity and contribution analysis of each tolerancing specification and corresponding fabrication cost, in addition to tolerance analysis, are employed for adjusting tolerancing of the spindle in order to ensure it satisfies precision requirement with lower fabrication cost.
For estimating fabrication cost, cost-tolerancing models for different fabrication processes are developed based on cost estimation data from engineering practice. Machining cost can be estimated using the developed cost model through calculating machining time and cost coefficientcorresponding to the machining process. Machining time is calculated from material removal as well as process parameters while fabrication cost is estimated according to processequipment, tool accessories, fixture, labor as well as administration and other costs. Based on this model, a computer spread sheet is also developed for the designer to estimate the fabrication cost in tolerancing design.
The main contribution of this study is to build cost-tolerancing model using machining time and the cost coefficient for estimating fabrication cost. This model, together with sensitivity analysis and contribution analysis, provide an approach for tolerancing design of a spindle that satisfies precision requirement with lower fabrication cost.
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