I mentioned yesterday that the RT was rotating "backwards". Say, if
the pointer arrow was at 20 degrees and I told it to go to 30 degrees
by saying

G0 A30

it would actually go backwards and stop at 10 degrees instead.

Well, I fixed it by reversing DC leads and by changing the sign of
INPUT_SCALE.

I am also sure that I have some kind of a tuning or mechanical issue
with the RT and will try to open it up on the weekend. It takes a lot
of torque to move (about 3-5 amps) and moves in a slightly jerky
fashion. It may also be a servo loop tuning issue too, purely a
software problem or a wrong setting of the onboard pots on the DC
servo drive.

i

Ignoramus31164 wrote:

I mentioned yesterday that the RT was rotating "backwards". Say, if
the pointer arrow was at 20 degrees and I told it to go to 30 degrees
by saying

G0 A30

it would actually go backwards and stop at 10 degrees instead.

Well, I fixed it by reversing DC leads and by changing the sign of
INPUT_SCALE.

I am also sure that I have some kind of a tuning or mechanical issue
with the RT and will try to open it up on the weekend. It takes a lot
of torque to move (about 3-5 amps) and moves in a slightly jerky
fashion. It may also be a servo loop tuning issue too, purely a
software problem or a wrong setting of the onboard pots on the DC
servo drive.

i

You've checked that the RT turns smoothly and without excessive drag by
turning the motor shaft manually with everything unpowered? No table
locks / clamps / brakes applied and dragging? CNC RTs often have
pneumatic operated table clamps that need to be released before
movement.

Next you need to work up a design and G-code to machine a mounting
bracket for your home switch and the ramp to trigger it.

On 2011-01-27, Pete C. wrote:

Ignoramus31164 wrote:

I mentioned yesterday that the RT was rotating "backwards". Say, if
the pointer arrow was at 20 degrees and I told it to go to 30 degrees
by saying

G0 A30

it would actually go backwards and stop at 10 degrees instead.

Well, I fixed it by reversing DC leads and by changing the sign of
INPUT_SCALE.

I am also sure that I have some kind of a tuning or mechanical issue
with the RT and will try to open it up on the weekend. It takes a lot
of torque to move (about 3-5 amps) and moves in a slightly jerky
fashion. It may also be a servo loop tuning issue too, purely a
software problem or a wrong setting of the onboard pots on the DC
servo drive.

i

You've checked that the RT turns smoothly and without excessive drag by
turning the motor shaft manually with everything unpowered? No table
locks / clamps / brakes applied and dragging? CNC RTs often have
pneumatic operated table clamps that need to be released before
movement.

I will look tonight. I think that I need to open it.

It IS hard to turn by hand. I tried this months ago.

Yesterday, I opened an end cover of the place where bevel gears turn
rotation by 90 degrees, and found some strange brown grease, which
seems like it is clean. I will try to remove the turntable tonight
to see how the worm system looks like.

I have not found pneumatic anything on it. I think that it is a VERY
early model of CNC rotary tables, basically the same as the U12 rotary
table, but with a servo motor and 90 degree direction changer, instead
of a manual handle. This suite me just fine.

There is a lock nut on it, but I thought that I loosened it.

I will take some pictures if I open it up.

i

Next you need to work up a design and G-code to machine a mounting
bracket for your home switch and the ramp to trigger it.