Re: [CAD_CAM_EDM_DRO] Servo-DRO advice sought

paragon032003 wrote:

>I was thinking of using components from cheap electric battery
>operated screw drivers that employ sun gears to generate a fair
>amount of torque to the shaft.
>
>

any backlash in the system leads to instability in the control loops.
These units are probably much too slow for reasonable movement
on a machine.

>The encoder would be a digital dro ( the ones that are similar to
>digital calipers but with mounting brackets) with an io connector.
>(Any other idears welcome!)
>
>

These units only update 2-4 times a second. That would allow precise
movement of about 10 inches/hour.

>The software I was looking at would be Linux EMC.
>
>Ok ....
>By having the encoders (DRO's) mounted directly to the x y and z axis
>of the mill any movement would be recorded and relayed back to
>emc ....... This would eliminate backlash issues as the physical
>position of the table is taken as opposed to motor shaft position.
>
>

No, it corrects for backlash errors, but TOO LATE. The motor has to
rev up in a hurry to get to the other side of the backlash, then slow to
a crawl to take up the backlash. In the meantime, the table is free to
be pushed around by the cutting tool.

>Could this work?
>

No, it will be a total disaster.

>What problems would I encounter?
>

Probably more than just the ones I have mentioned.

Jon