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A scratch inetersection based material removal mechanism for CMP processes ix proposed in this paper. The experimentally observed deformation pattern by SEM and the trends of the measured force profiles (Che et al., 2003) reveal that, for an isolated shallow scratch. the material is mainly plowed sideway along the track of the abrasive particle with no net material removal. However, it is observed that material is detached close to the intersection zone of two scratches. Motivated by this observation, it is speculated that the deformation mechanism changes from ploughing mode to shear-segmentation mode as the abrasive particle approaches the intersection of two scratches under small indentation depth for ductile metals. The proposed mechanistic material removal rate (MRR) model yields Preston constant similar to those observed experimentally for CMP processes. The proposed model also reveals that the nature of the slurry-pad interaction mechanism, and its associated force partitioning mechanism, is important for determining the variation of MRR with particle size and concentration. It is observed that under relatively soft pads, small particles and low particle concentration, the pad undergoes local deformation, yielding an increased MRR with increasing particle size and concentration. At the other extreme, the intact walls of the surface cells and the connecting cell walls between the surface pores deform globally, resembling a beam or a plate, and a decreasing trend in MRR is observed with increasing particle size and concentration. The predicted MRR trends are compared to existing experimental observations. [ABSTRACT FROM AUTHOR]

This paper reports an integrated approach for jointly solving the process selection, machining parameter selection, and tolerance design problems to avoid inconsistent and infeasible decisions. The integrated problem is formulated as a bicriterion model to handle both tangible and intangible costs. The model is solved using a modified Chebyshev goal programming method to achieve a preferred compromise between the two conflicting and noncommensurable criteria. Examples are provided to illustrate the application of the model and the solution procedure. The results show that the decisions on process selection, machining parameter selections, and tolerance design tan be made simultaneously with the model. [ABSTRACT FROM AUTHOR]

Variation propagation modeling has been proved to be an effective way for variation reduction and design synthesis in multi-operational manufacturing processes. However, previously developed approaches for machining princesses did not directly model the process physics regarding how fixture, and datum, and machine tool errors generate the same pattern on part features. Consequently it is difficult to distinguish error sources at each operation. This paper formulates the variation propagation model using the proposed equivalent fixture error concept. With this concept, datum error and machine tool error are transformed to equivalent fixture locator errors at each operation. As a result, error sources can be grouped and root cause identification can be conducted in a sequential manner. The case studies demonstrate the model validity through a real cutting experiment and model advantage in measurement reduction for root cause identification. [ABSTRACT FROM AUTHOR]