2 research outputs found
Automatic Support Removal for Additive Manufacturing Post Processing
An additive manufacturing (AM) process often produces a {\it near-net} shape
that closely conforms to the intended design to be manufactured. It sometimes
contains additional support structure (also called scaffolding), which has to
be removed in post-processing. We describe an approach to automatically
generate process plans for support removal using a multi-axis machining
instrument. The goal is to fracture the contact regions between each support
component and the part, and to do it in the most cost-effective order while
avoiding collisions with evolving near-net shape, including the remaining
support components. A recursive algorithm identifies a maximal collection of
support components whose connection regions to the part are accessible as well
as the orientations at which they can be removed at a given round. For every
such region, the accessible orientations appear as a 'fiber' in the
collision-free space of the evolving near-net shape and the tool assembly. To
order the removal of accessible supports, the algorithm constructs a search
graph whose edges are weighted by the Riemannian distance between the fibers.
The least expensive process plan is obtained by solving a traveling salesman
problem (TSP) over the search graph. The sequence of configurations obtained by
solving TSP is used as the input to a motion planner that finds collision free
paths to visit all accessible features. The resulting part without the support
structure can then be finished using traditional machining to produce the
intended design. The effectiveness of the method is demonstrated through
benchmark examples in 3D.Comment: Special Issue on symposium on Solid and Physical Modeling (SPM'2019
Haptic Assembly and Prototyping: An Expository Review
An important application of haptic technology to digital product development
is in virtual prototyping (VP), part of which deals with interactive planning,
simulation, and verification of assembly-related activities, collectively
called virtual assembly (VA). In spite of numerous research and development
efforts over the last two decades, the industrial adoption of haptic-assisted
VP/VA has been slower than expected. Putting hardware limitations aside, the
main roadblocks faced in software development can be traced to the lack of
effective and efficient computational models of haptic feedback. Such models
must 1) accommodate the inherent geometric complexities faced when assembling
objects of arbitrary shape; and 2) conform to the computation time limitation
imposed by the notorious frame rate requirements---namely, 1 kHz for haptic
feedback compared to the more manageable 30-60 Hz for graphic rendering. The
simultaneous fulfillment of these competing objectives is far from trivial.
This survey presents some of the conceptual and computational challenges and
opportunities as well as promising future directions in haptic-assisted VP/VA,
with a focus on haptic assembly from a geometric modeling and spatial reasoning
perspective. The main focus is on revisiting definitions and classifications of
different methods used to handle the constrained multibody simulation in
real-time, ranging from physics-based and geometry-based to hybrid and unified
approaches using a variety of auxiliary computational devices to specify,
impose, and solve assembly constraints. Particular attention is given to the
newly developed 'analytic methods' inherited from motion planning and protein
docking that have shown great promise as an alternative paradigm to the more
popular combinatorial methods.Comment: Technical Report, University of Connecticut, 201