[FoRK] Those wacky MIT students: a handheld CNC router

Ken Meltsner meltsner at alum.mit.edu
Mon Aug 27 16:14:36 PDT 2012

Handheld CNC router -- interesting idea, not sure if it actually makes
sense.  The one useful comment at the Fine Woodworking site where I
found this pointed out that it's still possible for the user to
overshoot the correct position and remove wanted material, but I think
the potential goes further than a replacement for hardboard templates.

The tool is interesting for a deeper reason.  Woodworking (and many
other handcrafting techniques) balances risk, effort, and results.
It's straightforward to set up a template for a lathe or router that
will give you an accurate result but that result often seems
mechanical or "cookie-cutter."  The most impressive work often
requires careful handwork with the potential of completely botching a
nearly finished piece -- consider the sort of shapes one can get with
handblown glass, for example, vs. the relatively pedestrian products
made in molds.  Or the rounded edges of furniture designed by the
Greene brothers -- the rounding does not have a constant radius along
the edges, and required careful use of an unjigged chisel to yield the
desired effect.

With smarter controls, the tool's descendants might provide quality
comparable to a skilled craftsman's work.  Or not, if it turns out to
be too hard to describe numerically the sort of "organic" curves that
many people respond to.

"Many kinds of digital fabrication are accomplished by precisely
moving a tool along a digitally-specified path. This precise motion is
typically accomplished fully automatically using a computer-controlled
multi-axis stage. With that approach, one can only create objects
smaller than the positioning stage, and large stages can be quite
expensive. We propose a new approach to precise positioning of a tool
that combines manual and automatic positioning: in our approach, the
user coarsely positions a frame containing the tool in an
approximation of the desired path, while the device tracks the frame's
location and adjusts the position of the tool within the frame to
correct the user's positioning error in real time. Because the
automatic positioning need only cover the range of the human's
positioning error, this frame can be small and inexpensive, and
because the human has unlimited range, such a frame can be used to
precisely position tools over an unlimited range."



Ken Meltsner

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