What's new
What's new

Any OmniTurn experts around?

DocsMachine

Titanium
Joined
Jan 8, 2005
Location
Southcentral, AK
I'm getting a GT-75 up and running, and have been practicing writing and cutting a few test parts. My skill level with such things is still very much on the 'neophyte' level, but I'm tryin'. :)

I have two questions:

One, on the X-axis servo, is a small pneumatic ram or actuator:

actuator.jpg


This is fed low pressure air from one of three regulators in the cabinet below the work area, and when I got the machine, the line feeding it- which had already been patched at least twice- had popped off, and had apparently been that way for quite a while.

The manual warns against trying to move the axis without air pressure, so I'm assuming this thing is a sort of brake considering the steep angle of the X slide.

While testing, it's thrown up errors three times, saying the servo 'can't hold position'- twice while at extreme lower travel (very possibly reaching the limit OF travel) and once when the slide was more centered.

Am I right in thinking this thing IS a brake of some sort? It's not mentioned or shown in the manual, just the warning about moving it without air pressure. If so, it's been moved and probably a lot without pressure, as the hose looked like it'd been laying in the swarf and coolant for a good long time.

Has anyone ever been into one of these, or a similar device?

The other issue is I can't seem to get it to thread. I've followed the book closely- G33, a 'canned cycle'- and whenever the program reaches that line, motion stops (but the spindle and coolant keep going) and then the screen gives me something that looks more like a DOS error screen than an OS error dialogue.

First tried threading a part I'd turned, then tried just a thread on a raw bar. Seems that when it reaches that G33 line, whether that code or something else in the line, it chokes and can go no further.

The screen does give me some code- something like an "error 9", maybe, but I never thought to take a photo of it. No idea what that means.

I thought maybe the spindle encoder was bad, but in the 'troubleshooting' section of the manual, they show you how to test it- basically Ctrl-S in Jog mode turns the "RPM" readout into straight encoder-pulse counts. It should count up to 3999 and then go back to zero- zero is the index mark. Mine worked perfectly, just as the manual describes.

I have the newer "Gen 4" controller, and I know there's a "new" and an "old" version of that- I'm not sure which I have (probably older) but the threading code and description is identical- down to the typos- in both 'new' and 'old' manuals.

Any ideas? I'll be calling OT later this week, but figured I'd ask here, see if anyone's run across either of these issues before.

Doc.
 
Well, at least as far as the threading goes, put that one down to operator malfunction. :)

When it asked for the thread pitch, stupid me gave it TPI instead. It was trying to cut a 16" pitch thread, and so, of course, errored out.

Give it a proper 0.0625" and fancy that, it works! :D

Doc.
 
I have 2 running converted machines. Y axis is horizontal so no need for a brake when the machine is off. Seems logical your machine would need a brake. Fail safe is if the pressure goes the brake applies? When powered off I can push on either axis and move the slides. I guess a 12 inch slide with 10 tool holders would weigh enough to move it when mounted near vertical. Your servos will push to maintain the location if the brake is trying to keep it from getting there, it would seem that an overload could take place. Mine with older controls will trip the axis breakers when trying to maintain a position against spring pressure. On mine there are Bellville springs on each axis to soften the blow if you over travel in rapid. If you creep up to the limits and let it sit there they will trip out after a few minutes. If that brake is dragging you would see the error more often when trying to going "up hill".
All this said the fellows at Omniturn are very helpful in solving problems. I would bet they have a modestly priced kit for fixing the air lines. I have an air collet closer on one of mine and the plastic lines got hard and cracked after about 15 or 20 years. They were most helpful in getting that fixed.
 
Thank you, sir.

The lines weren't necessarily the issue. That's all pretty standard 1/4" push-to-lock pneumatic tubing and fittings.

I'm worried that, as you say, the air disengages the brake (the air routing into the ram is to retract) and being without an air connection for a fair amount of time, whatever it uses as a "brake pad" is likely burned out or worn off by now.

Doc.
 
Thank you, sir.

The lines weren't necessarily the issue. That's all pretty standard 1/4" push-to-lock pneumatic tubing and fittings.

I'm worried that, as you say, the air disengages the brake (the air routing into the ram is to retract) and being without an air connection for a fair amount of time, whatever it uses as a "brake pad" is likely burned out or worn off by now.

Doc.

I would expect that also. Maybe whoever tied it in the open position to make it run without air. Omniturn will be most helpful either way. If you are forced to run without the brake I would run it down hill before powering down so the slide would have less momentum when it hit the "soft stop". If that is near zero powering up and homing will be easier. If that is the wrong direction homing will be a minor pain.
 








 
Back
Top