Meaning
Mathematical ratios describing the spatial efficiency of parts within a mould or on a sheet determine the material waste in production. The nesting index compares the total area or volume of the finished parts to the total area of the feedstock or the mould footprint. It functions as a metric for optimizing the layout of cavities in injection moulding or shapes in sheet extrusion.
This measurement accounts for the gaps between parts and the width of the runners or scrap edges.
Spatial Efficiency
Layout optimization aims to maximize the number of units produced per cycle. High nesting index values indicate a dense arrangement that uses almost all the available material. Poor nesting leads to large amounts of regrind or scrap which increases the total part cost.
Economic Impact
Material utilization directly affects the profitability of a moulding run. When the nesting index is low, a larger percentage of the resin is spent on non-functional features like sprues. Reducing the distance between cavities can improve this ratio and lower the energy required per part.
Tool Design
Engineering the runner system is the main way to influence the spatial ratio. High nesting index values are achieved with hot runner systems that eliminate the waste of solidified cold runners and allow for tighter part spacing. Balancing the cavity layout ensures that each part fills at the same rate while maintaining a high density.
