Material Utilization and Part Nesting for Hard Tooled Sheet Metal
The material cost of a sheet metal part is based on the rough mass required to make the part. The utilization is equal to the finish mass of the part divided by the rough mass—rough mass includes any material scrap.
aPriori provides multiple methods for computing sheet metal material utilization. By default, aPriori uses different methods for different kinds of processes:
• For progressive die, aPriori uses a true-part shape nesting (TPSN) algorithm by default. In order to maximize material utilization and minimize waste, this algorithm finds the tightest nesting for parts using the blank’s actual perimeter. Note that the TPSN algorithm used by progressive die (and transfer die—see
Sheet Metal—Transfer Die) differs from the TPSN algorithm used by soft-tooled processes (see
Sheet Metal—Soft Tooled) in the following respect:
o Progressive die: uses an optimized strip-nesting algorithm in which parts are nested in rows, and all parts in a row have consistent orientations.
o Soft-tooled: allows neighboring parts to have different orientations, and doesn’t constrain parts to be organized into rows.
• For other hard-tooled routings (that is, hard-tooled routings other than progressive die), aPriori uses rectangular nesting by default. This algorithm considers length-wise and width-wise orientations using the blank’s smallest enclosing rectangle.
The Material Selection dialog (in the Manufacturing Process pane) provides you with four options for calculating utilization:
• Rectangular Nesting: assumes the part is rectangularly nested on a sheet, with either a lengthwise or widthwise orientation (whichever is more efficient).
• True-Part Nesting: for progressive die, uses the component’s actual perimeter to determine nesting, and tests various rotations of the component. See also
Blank XY Orientation within Part Strip for more information on progressive die strip nesting.
• Machine Default: uses the current machine’s associated average material utilization (the machine property Avg Utilization); use this to estimate material costs for dynamic nesting.
• Override: uses a fixed utilization value entered by user; use this when you know the exact utilization based on a supplier’s nesting pattern.
VPE administrators can customize the default utilization method with the cost model variable defaultUtilizationMethod.
The current nesting pattern on the currently selected stock is viewable in the Viewer using the Analysis menu. The stock can be changed via the Material Selection dialog.
Setup options for controlling trip strips, margins, and addenda are available—see
User Inputs for Hard Tooled Sheet Metal.