An automated random stacking tool for packaged horticultural produce

Abstract

One of the major obstacles to the modelling and optimisation of horticultural cooling processes is the construction of an accurate 3D bulk fruit geometry. When a collection of horticultural products is packed into a box, the shape of the individual fruits or vegetables combine to form a stack with a complex and convoluted shape. The precise shape of the stack may have a significant impact on the airflow pathway and hence the rate of transfer processes in the system, such as cooling. Thus it is important for a realistic model for cooling of stacked, packaged fruit to have the capability to explore sensitivity to the randomness of possible stacking outcomes. Numerous realistic stacks of fruit may need to be generated to enable subsequent simulation to quantify effect in outcome. In this paper a new tool is developed that is capable of rapidly generating the geometry of a fruit stack. The tool (implemented in Blender) takes a size and weight distribution of fruit (in this case Hayward kiwifruit) and simulates the effect of gravity and friction forces to form a realistic stack. The tool-generated stacks were validated against CT scans of real fruit stacks and found to be similar, except that in the CT scans the presence of an internal polyliner appeared to hinder the occurrence of fruit in the bottom corners of the stack, which was not simulated in the stacking tool. Generating a stack required only 150 s on a desktop PC, which makes the tool viable for integration with other simulation systems to optimise packaging design. Automated methods to generate a realistic polyliner shape were also developed, and the tool was used to predict box volumetric efficiency to within 2%.