Re: [CAD_CAM_EDM_DRO] Re: Re: Re: Electronic Lead Screw & Power Cross Feed | Poor Man''s CNC ?

I keep reading what Mach3 wont do in regard to encoders in theory. It's a bit frustrating as I see everyday what it does.

A machine I recently retrofitted with Mach3 and encoder feedback to the PC. Put Mach in "reset" and it has a screen with nothing but DRO's for manual operation.

Here are the specs:

X and Y axis are 12,800 steps per inch, max rapid rate is 140+ ipm on both 5 tpi ballscrews (.200" lead) (3.2:1 belt reduction)

Z axis is 20,000 steps per inch. 10 screw revs per inch. .100"lead (4:1 belt reduction) Z rapids at 60 ipm (driving the knee).

All three axis's are monitored by their encoder in Mach, if position is lost the machine is halted.

Mach in 45 khz mode, all three axis's can be rapid simultaneously and no lost steps are encountered. It will actually go faster.

Do the math on the above for the true pulse/count rates.

The machine can be seen here, the white JET 836: (disregard my dirty shop..thx)
http://machsupport.com/forum/index.php?topic=2.0

The board used is at:

www.rogersmachine.net

Ron





Jon Elson <elson@...> wrote:
John Stevenson wrote:

>>Vaso wrote:
>>
>>
>>
>>>Bob:
>>>
>>>You've done an excellent review of the entire issue. Full CNC is
>>>clearly far more complex than electronic lead screw - and requires far
>>>more learning time. CNC leads to a different lathe machine altogether
>>>- where "machining" is replaced by "programming" - even for simple
>>>one-off pieces. I understand - once converted to CNC - a "CNC lathe"
>>>cannot be a good "hands-on" manual lathe - except maybe with expensive
>>>electronic handwheels.
>>>
>>>
>>>
>>>
>>Not necessarily true. We have a Bridgeport/Romi CNC lathe at work that
>>can be used manually as if it only had a DRO. You might notice a slight
>>drag on the handwheels, that is about the only sign. I don't see why a
>>CNC setup that preserved the handwheels couldn't be used manually.
>>It would need either low-cog stepper motors or servos. If the servos
>>had feedback to the computer, then it could act as a DRO when not in
>>CNC mode.
>>
>>Jon
>>
>>
>
>Mach3 does just this. A seamless swap over from manaul to CNC with the displays acting as DRO's
>
>

With a number of limitations. For instance, the encoders can never
exceed about
30,000 counts a second or there is the possibility of lost counts, since
this is
a software-only encoder counter. And, of course, you need to have encoders
and servo motors to read the position at all.

Jon



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