Re: [CAD_CAM_EDM_DRO] questions for new cnc user

scott_in_tucson2002 wrote:

> Hello,
>
> I'm a new cnc user, and I have a couple of questions. I have a
> sherline 5500 milling machine. I'm using some powermax II stepper
> motors with gecko 201 (just 201, not the 'a' version) drives. The
> g201's are connected via parallel port to a dos machine. For
> software I'm using cncpro.
>
> 1) My steppers are 1.8 degree/step, the sherline is 20 revolutions
> per inch, and the gecko is a 10-microstep driver, so I compute
> 40,000 steps per inch. However, when I command the software to move
> 1 inch, it only moves (approx) 0.75". Where did I go wrong?

Is it approximate, or is it exact. Using a dial indicator, move 1" away,
and then back. Does the position repeat exactly each time, or is there
some fluctuation in the position. If it repeats exactly every time, then
I would guess maybe your 10 x microstepping is set wrong, and
you are really getting x 7 or x 8 step multiplication. By careful
measurement,
you may be able to determine the exact numerical basis of the problem,
and that may suggest WHAT the problem is. Make sure you approach
all reading points from the same direction to eliminate backlash from
the results. What constrains the leadscrews? Do you have ball bearings
or are you just using the motor's bearings? The motor's bearings might
allow
end play in the screw.

> 2) I've tried using some software (DeskEngrave) to engrave TTF
> fonts. I'm using a 3/16" end mill. The problem I'm having is that
> the end mills are centered on the edges of the font characters,
> resulting in really fat characters. I would rather have the end
> mills moving inside the character, with the edge of the end mill
> matching the edge of the character. (I hope this makes sense). Is
> there a common way to do this? Is there better (freeware/shareware)
> software for engraving text?

I can tell you that Bobcad doesn't do much better.

Jon