Re: [CAD_CAM_EDM_DRO] CNC division

Hi Tony,

Good points! You're saying that MaxNC enters steps per degree? Not
steps per revolution of the table? THAT'S BAD! (Hope CNCpro isn't
doing that). The linear axis for MaxNC are entered as steps/inch, I get
8000 for the Sherline setup and 1/2 step drives.

I just fired up a demo copy of MaxNC from (TMG site), and it shows "A
RESOLUTION" expressed as a DECIMAL. (80.0000) And it takes 44.4444
just fine! I will be trying it (in one direction only) ;>) after
getting new bipolar steppers installed on my mill and rotary table.

I agree with you, this would be a serious flaw for a software program!
But unless I've missed something, MaxNC "TMG" and "DLX" should be fine!

Alan KM6VV


Tony Jeffree wrote:

>
> At 01:00 06/04/2001 +0000, you wrote:
> >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!
>
> Depends on what you're using to control the 4th axis. For example, in the
> MaxNC software, setting up the 4th axis involves configuring the number of
> steps per degree. So, if your drive system doesn't result in an integral
> number of steps per degree, any rotary moves you make will generate a
> positional error. For example, if you had a 40:1 worm drive & a directly
> connected stepper, this would give 16000 (half) steps per 360 degrees,
> which is 44.4444r steps per degree. The best you could do with MaxNC would
> be to set 44 steps per degree, so you would get .444 steps error per degree
> of movement - 160 steps in a full rev, approx. 4 degrees out. Absolutely no
> good if you were doing anything critical, like milling a gear wheel. So,
> the only option with Max is to use a drive system that results in an
> integral number of steps/degree. Bad software design in my opinion - if
> they had chosen steps per 360 degrees, it would have accommodated any
> dividing head/rotary table ratio that you had to hand. As it is, you can
> only work accurately with MaxNC if your rotary table's drive ratio is a
> multiple of 9, so the "conventional" rotary table ratios of 40:1 and 60:1
> don't hack it without using additional gearing between the stepper & the
> worm. This makes 72:1 and 90:1 dead convenient for users of the MaxNC
> software.
>
> Regards,
> Tony