Re: CNC newbie questions

John:

I've just completed adding CNC to my the Model 2000 CNC ready mill.
I can't comment on Sherline's stepper motors - I used US Digital
MS23's with a running torque of 114 in-oz. Due to various projects
that I'm working on, I used Gecko 201's as the stepper drives.
Others using the Xylotex seem to be quite happy with their choice.
The power supply is one of my own design 10A 40V driving three 4A
motors. It does work well. The sizing of power supplies in the
Gecko white paper is correct.

TurboCNC works well. It has its own idiosyncracies as does every
implementation of a G-Code interpreter. Download the latest version
3.24C from the newsgroup http://groups.yahoo.com/group/turbocnc files
section. V4 should be released soon and will, providing added
functionality, and a more user friendly interface.

Just a hint: http://cgi.ebay.com/ws/eBayISAPI.dll?
ViewItem&item=2559085195&category=25276

Tony



--- In CAD_CAM_EDM_DRO@yahoogroups.com, "john_haddy" <jhaddy@c...>
wrote:

> Hi all,
>
> I'm about to embark on an investment in CNC and have opened
> a can of worms, I think!
>
> I'll be buying a Sherline 2010 mill and proably using
> Sherline's steppers, unless somebody on this list advises
> me that I need better motors.
>
> I'll either make my own microstepper controller (4-axis), or
> maybe will use Xylotex boards.
>
> Now for the questions: (!)
>
> 1/ Does anybody consider the Sherline steppers to be underpowered
> for the machine? (I assume the main limitation is in the maximum
> usable step rate?)
>
> 2/ I'm having trouble understanding the power supply requirements
> that I've seen documented (e.g. in Gecko Drives' white paper).
> Assuming the motor is at rest in the 45 degree step position, where
> the motor will need the maximum current, each winding needs to be
> powered with Iwinding = Imax/sqrt(2). From this, it would appear
> to me that the drive power supply needs to provide an average
> current of 2 x Iwinding = 1.4 x Imax
> This conclusion doesn't gel at all with the requirements in the
> white paper (in that my calcs show a MUCH gruntier supply is
> needed), so I'm confused as to where I've got it wrong.
>
> 3/ Any suggestions/recommendations as to CNC software? I've looked
> at DeskCNC, Mach2 and TurboCNC. Each seems to have ups and downs.
>
> DeskCNC has a serial interface to proprietary hardware, which
> appears to avoid PC hardware compatibility issues, and it includes
> some CAM functionality. I'm not sure about it's ability to
> support 4 axes in either CAM or CNC. I was advised that it does
> but the downloadable S/W doesn't seem to.
>
> Mach2 supports 4 axes but may limit my computer installation, since
> it needs to do naughty things to get Windows to be pseudo real

time.

> It also doesn't have any CAM, so I'd need to sort a solution out
> there (Suggestions welcome).
>
> TurboCNC gives me the option of using a really cheap PC running DOS,
> at the expense of lower step rates. I haven't had a chance to look
> at this closely yet - I don't know whether it can handle 4 axis
> control.
>
> At the moment I guess I'm leaning toward Mach2, if I can sort out
> the CAM issue. Maybe I'll have to bite the bullet and buy
> BobCAD/CAM. I have access to SolidWorks so I wasn't really that
> keen on having to shell out for a CAD package I don't really need
> at the moment.
>
> Any others I should consider?
>
> Thanks for any assistance for the newbie,
>
> John Haddy
> Sydney, Australia