Optimization of guillotine shearing operations

A guillotine shear machine is modeled for blank-to-sheet optimization. Low volume production, which is the case studied, is highly inefficient for direct labor, direct material, and machine utilization. This study recommends general rules of operation under the conditions of variable job-lot quantities and blank layouts given limited choices of standard sheet dimensions. Stated differently, what is the sheet size and blank orientation that drives optimum material yields and labor efficiency when the blank dimensions are set by the product design? A data base of 180 cost estimates is determined by allowing the rectangular blank size, sheet stock size, layout orientation, and job quantity to vary. Results indicate there is a linear relationship between the number of blanks per sheet and material yield, but superior material yield and labor efficiency, and hence lowest cost, is achieved by orientation of the length-of-blank to the length-of-sheet. While this result is statistically relevant to the data base, sufficient evidence is presented to permit its generalization. Trends indicate that cost variance between designs decrease with increasing job quantities. It is shown that material cost dominates labor considerations in the determination of part cost for guillotine shear operations.