Re: CNC division

Hi Rab,

I'm in a similar point in my "4th axis thinking". Yes, even steps per
degree sounded like a nice idea. As I've just said in a previous post,
Sherline's 72:1 worm and 1/2 stepped 200 step stepper gives 80 steps to
the degree. But unless you're doing it "by hand", I don't think it
matters!

I'm not fully decided, but I THINK I'd rather not have the table "wrap
around", I.E., I'll go from 300 deg to 400 deg, when I want to get
around to 40 deg again. If I "wrap" a long rotary move to my 'Y' axis,
it works this way. If I want to cut 3 threads, I would just go 360*3
degrees.

I DID do "wrap around" calculations for a stepper motor driving a
gearbox to rotate a beam antenna. Made sense there!

I'm open to other's thoughts, this IS a confusing issue. Similar to
figuring out G02/G03 cuts with start angle at 300 deg, and end angle at
40 degrees (CCW). BUT, you might want to cut CW, the LONG way around!

Alan KM6VV

rab@... wrote:

>
> 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
> Taig headstock and driving that via the Z axis from Master5CNC, which
> seems to give good results. 72 and 90 tooth wormwheels seem to be
> quite common as well.
> I am quite new to this side of it, so if you find a definitive answer
> as to best practice, please do pass it on.
>
> Do you know what happens in the A axis when you go beyond 360
> degrees ? Does the work rotate back to the start or take the shortest
> route "through" the 360 mark ? In using the Z axis for my machine I
> had to work out a way for the software to keep track of the number of
> revolutions it was on and add 360 per revolution while taking the
> shortest route between points. Is there a better approach ?
>
> Rab
>
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