Re: How Would You Design question

Hi Tim,

It seems from your post that you want to hold a 37 inch long piece of
wood, and have it pass the blade to cut thin slices, 37 inches long.

a moving table holding the wood would need a sturdy clamping system
and about 7 feet of actual travel.

on the table you would need to advance the part by small ammounts.

this should not be too difficult, as once the first cut is made, all
remaining cuts can be referenced from the previous cut.

It seems then that your choices fall to moving the whole 7 ft slide
assembly forward by 4 inches, or to mount the part advancement on the
table and just move the part forward by the 4 inches.

The feed rate is not a critical design problem as you can easily
accept a large variance from actual. ie: 8 ipm or 8.5 ipm would not
be a problem.

the slow and accurate 4 inch feed could easily be a micro adjustment
at a maximum of one IPM.

I would look into timing gears, leadscrews and linear rails.

To meet your $$ you will need to get surplus, but I think if you
doubled your $$ you could buy new.

If on the other hand, you are making 3x4xthin wafers, a chop saw
design could be done with less.

Dave

--- 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