Search Results

Controlling the Cost of Variance is essential to the manufacturing process of Printed Circuit Board Assembly for low volume high mix production. The material variance is identified as the additional components and resources consumed beyond the minimum required to complete the project. This Quantity Variance occurs at the effects of defects at key steps of the manufacturing process. Such occurrences result in the need to purchase additional components for the completion of the order. These additional components termed Quantity Variance alter the sequence of the manufacturing process affecting quality, timely delivery of the job and directly impacting company profitability.

A study was performed to determine the effects of varying the wall thickness and material glass fiber concentration for parallel and perpendicular shrinkage rates for a constrained thin-walled box shaped component. An analysis of the shrinkage for the bottom portion of a 3 dimensional constrained thin walled injection molded component was performed using measurements made from bitmap images of the components that were obtained from a traditional flatbed scanner. The shrinkage rates were determined by comparing mold cavity hatch lines to the correlating transposed hatch lines on the plastic molded component. The perpendicular and parallel shrinkage rates were determined and are discussed as a function of thickness and glass fiber content. A wide range of processing control factors was used in the study.