Re: [CAD_CAM_EDM_DRO] Re: CNC division

----- Original Message -----
From: <rab@...>


> I'd have thought that using any ratio of wormwheel and / or pulleys
> that will divide up cleanly into 360 should be a good start, so that
> a specified number of steps will give you exactly one whole degree.
> I'm testing a 120 tooth wormwheel with a 200 step motor to turn a

Hi,

This is really the point I was making - most divisions DON'T divide cleanly
into 360. Wheel counts which I often have to divide include 7, 11, 13, 17,
54 and 366, none of which divide cleanly into 360. I appreciate that, by
drawing the wheel out in a CAD program, it should be possible to generate
g-code which minimises errors but I actually want to do something a little
more complicated than the norm and was hoping there might be a way to
separate the division from the cutting. I'll explain - What I am wanting to
achieve is cutting unusual, specialised tooth forms by generating them. If
you can imagine a disk with 13 maps of Italy sticking out from the edge this
will give some idea of the shape of a watch escape wheel. To cut such a
wheel normally involves buying or making 4 or 5 special cutters at a cost of
around 40UKP each - not very realistic for a one-off. So, I reckon that,
with a bit of clever maths, it should be possible to persuade a little cnc
mill to generate the form by coordinated movements of the A, Z and Y axes
while running the thin, round edged slitting saw cutter back and forth with
the X axis. I haven't yet found any software which would seem able to
produce the g-code for this from a dxf file (unless you can suggest one) and
so am almost resolved to coding it manually, in which case, having a method
of producing a 'loop' to do the tooth shape and a separate 'loop' to index
from one tooth to the next would seen to be easier than coding the whole lot
as one long file.

Perhaps I am wrong, I have been before - it was Tuesday I
think.....196x..... ;O) <g> Any sugestions or observations would be very
welcome.
Thanks to everyone else who has replied on this thread.

Ian
--
Ian W. Wright
Sheffield UK
www.iw63.freeserve.co.uk