Characterization and control of pin diameter during in-mold assembly of mesoscale revolute joints

TitleCharacterization and control of pin diameter during in-mold assembly of mesoscale revolute joints
Publication TypeJournal Articles
Year of Publication2009
AuthorsAnanthanarayanan A, Gupta SK, Bruck HA
JournalNorth American Manufacturing Research Institute
Date Published2009///

Macro-scale revolute joints can be formed byfirst 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 macro-
scale joint can be controlled by carefully
selecting the process parameters and the
material for the pin. However, in order for this
strategy to work at the mesoscale, it requires the
use of very thin cores to form sub-millimeter
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 macro-scale. At the
macroscale, as the hole shrinks on top of the
pin, the joint is jammed. So a fundamental
question is why this counter-intuitive 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.