CHARACTERIZATION AND CONTROL OF PIN DIAMETER DURING IN-MOLD ASSEMBLY OF MESOSCALE REVOLUTE JOINTS

摘要

Macroscale revolute joints can be formed by first molding the hole and then molding the pin inside the hole. As the pin shrinks during the solidification process, it moves away from the hole and provides the clearance for the joint to function. The value of clearance in the macroscale joint can be controlled by carefully selecting the process parameters and the material for the pin. However, for this strategy to work at the mesoscale, it requires the use of very thin cores to form submillimeter holes. Such thin cores are very difficult to make, are easily damaged during the molding process, and very difficult to retract from the hole. Our previous work has shown that making the pins first and then creating holes on the top of pins leads to successful mesoscale joints. This strategy is counter intuitive based on our experiences at the macroscale. At the macroscale, as the hole shrinks on top of the pin, the joint is jammed. So a fundamental question is why this counterintuitive strategy works at the mesoscale. In this paper we show that at the mesoscale, the joint jamming is prevented because of the deformation of the pin under the compressive loading during the second-stage molding. We also describe features in the mold that can control the pin deformation and hence control the joint parameters. We present experimental data and computational models to show how mesoscale revolute joints can be formed.