Balsa thicknessing was Re: How Would You Design question

Alan,

From the dims given (and the use of the word "sheets", instead of
strips), I'd guess balsa sheets for model airplanes, etc...

Tim,

Most of these are cut commercially by bandsaw setups, then sanded to
thickness. If your use IS structural, I'd be wary of using the
tablesaw cut "as is"

Even an Ulmia 6 kilobuck saw (or a $20K altendorf) will introduce
slicing of the external fibers, which will weaken the output product
considerably. Partly by the reduced thickness in the area OF
the "slicing" path of the circular blade through the material, and
partly from the localised stress which will be the result OF
these "sliced" fibers. (AND a tablesaw blade will likely leave a lot
more stock as waste sawdust, compared to the Bandsaw- even with thin
kerf TS blades)

The mechanics of the carriage of a sliding table saw like the
altendorf would be a good place to start, IMO. (Even deltas' version
for the unisaw might work, since your pieces are only 37 inches long)
I knew a dulcimer maker who set up a bandsaw to cut sides (very
similar to what you envision) automatically. NO cnc involved at all!

I'd control the FENCE by cnc, and the carriage by pneumatic/electric.
You need straightness, but not necessarily the "captured" effect of
expensive linear bearings. Use a "low-pressure area" on the fence
(vac pulled through mdf) to minimise re-cutting of the material

This is a fly to swat, no need for a sledgehammer, IMO.

Hope this helps,

Ballendo

P.S. If volume is anticipated, put some digital control on the
sander. Maybe even some "homemade" in-process SPC. Check out the
operations of people cutting woods for musical instruments. Their raw
material (like yours) is relatively expensive, and must be cut
economically into thin sheets. And you aren't too far from some balsa
suppliers in the midwest. Others have done what you are trying to do,
and success leaves clues...

--- In CAD_CAM_EDM_DRO@y..., "rcstickman" <alantrest@h...> wrote:
> Hi Tim,
>
> Correct me if I am wrong but I am trying to picture this project in
> the correct light.
>
> This sounds something like a linear cut veneer saw's operations.
> Does this sound accurate?
>
> Alan Trest
> Pensacola Florida
>
>
>
> --- In CAD_CAM_EDM_DRO@y..., "Tim Goldstein" <timg@k...> wrote:
> > Been thinking about creating a specific purpose CNC machine and
> thought it
> > would be help to see how some of you would attack the problem.
The
> question
> > revolves complete around the mechanical design of the equipment
and
> does not
> > at all consider the electrical or software from the motors to the
> computer.
> >
> > Here are the design parameters:
> > 1) The machine will be single purpose to cut sheets of wood off
of
> blocks
> > with a maximum dimension of 3" x 4" x 37"
> > 2) The resulting sheets need to be consistent in thickness over
the
> lenght
> > of the sheet + - .0025
> > 3) The thinnest sheets cut will be .050" and the thickest will
> be .200"
> > 4) The cutting motion travel will need to be in the speed range
of
> 20 - 60
> > ipm with a rapid backfeed in the 200+ ipm range.
> > 5) The actual cutting equipment will be a high end table saw with
> very good
> > bearings so that the spindle rigidity, run out, etc do not need
to
> be part
> > of the design discussion
> > 6) The designed mechinism has to fit on and be compatable with a
> high
> > quality table saw
> > 7) The mechanical portion of the design (not including motors,
the
> base saw,
> > electronics, or software) should be able to be constructed for
> about $500
> > 8) Specifying expensive components that are commonly able to be
> found in the
> > surplus market to meet the cost goal of #7 is acceptable.
> >
> > I think that pretty well lays out the general requirements I am
> trying to
> > meet. Look forward to the various ideas that everyone may have on
> how to
> > accomplish this. I have some ideas in mind and it will be
> interesting to see
> > if they are consistent with the group consenses.
> >
> > Tim
> > [Denver, CO]
> > http://www.KTMarketing.com/CNC.html