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

John Stevenson wrote:

>
>
>>>>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
>>
>>
>
>Jon,
>As Mach3 uses a single pulse encoder the 30,000 counts a second don't apply.
>True you need an encoder but so will a black box and that will also need the stepper or servo to drive the screw.
>I know of one guy using mach3 commercially threading 1/8" BSP [ 28 tpi ] taper thread at 1,000 rpm to a shoulder.
>same applies to 1/2" x 20 tpi UNF.
>
>Surely that's proof ?
>
>

I guess a sub-thread has gotten off the original thread and subject
line, and the 30,000
was in reference to the leadscrew encoders or step pulses.
Specifically, I was replying
back about Mach3 monitoring following error by watching the encoder
signals in software,
without a hardware encoder counter. The post that started that
sub-thread was about
not being able to use a lathe as a manual machine after doing a CNC
conversion, except
by using the jog keys. So, I said our Bridgeport/Romi lathe is a
PERFECTLY fine manual
lathe, and if you didn't use the CNC feature, you really would think it
was a manual machine
with a rather odd looking DRO setup.

Jon