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

Sounds good Mariss! How about a white paper?

Also can you ratio to an axis that is already ratioed? In other words
in your example ratio y to the x axis which is already ratioed. The
net result would be a linear taper.

Dave


Mariss Freimanis wrote:

>I didn't realize this is such a big thing. Reason I say that is I
>added "ratio" to to the G-Rex instruction set but thinking it would
>be a semi-useless instruction.
>
>Ratio (RTO) causes an axis to select a target and follow it at a
>fixed ratio. It works like this:
>
>Say you have a 500-line encoder on your spindle and you have a 10-
>microstep drive. The spindle will genererate 2,000 counts per
>revolution and the drive will move at 2,000 steps per rev. Both are
>equal.
>
>Let's also say you want the step motor to move at 1/10 the spindle
>speed. The step motor is in the x-axis group as is the encoder. You
>would send the following insruction to the G-Rex:
>
>RTOxENCx+1000000000<cr>
>
>Meaning "have the x-axis motor track the target ENCoder x at a ratio
>of 0.1000000000 of the target's speed." The step motor would follow
>the spindle speed (position) in the same direction to a 10-place
>accuracy. That should be good enough for most folks.
>
>That's all there is to it. Connect a laptop to the G-Rex via USB,
>download that line of code from NotePad, disconnect and walk away.
>
>Mariss
>
>
>
>--- In CAD_CAM_EDM_DRO@yahoogroups.com, Jon Elson <elson@p...> 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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