Robotical Handling of Polyurethane Foams with Needle Grippers

Abstract

The handling of non-rigid materials implicates different problems than handling usual rigid parts. The soft polyurethane foam is widely used in the production of car seats. Automating the handling of these materials requires special gripping methods. In this paper we focus on the needle gripping method. This method is based on a set of needles penetrating into the foam and lifting the foam by using the frictional force between the needles and the foam. A mechanical model is proposed for the calculation of the force needed to pull out a needle from a foam part. The theory is based on continuum mechanics and fractal geometry. The theory is then compared with the test values and measured results. A method for the principle of designing a needle gripper is also presented and explained on a newly developed gripper.