[John3]

Hi, I need a little help with Swiss Slant Lathe controlled by a Dual Fanuc 0-T.

The problem is two fold;

1. The Main spindle X-Axis behaves differently at the negative "-" end of travel compared to the positive "+" end of travel.

When I handwheel to the + limit, the position screen switches to an X-Axis overtravel alarm "510 OVERTRAVEL X+". All that have I have to do to recover is crank the other direction and reset the alarm.

If I handwheel to the - limit, a relay drops out and the position screen only changes with the addition of a message "NOT READY" in the lower left. To recover from this I have to Re-Zero-Return all 5 axis. And something crazy happens to the X axis absolute coordinate value (problem #2).


2. After a not ready condition (as caused by above) the X-axis absolute display (and command position) has an extra offset amount added to its value. The machine X-axis value is still the same. The machine zero point matches before and after the NOT READY condition. However, the absolute position display has an extra offset added to it. This extra offset value is the X value when the NOT READY occurred. I cannot figure out how to clear this errant absolute X-axis value offset other than power cycling the machine. It must be stored in a parameter somewhere????

Thanks in advance for any thoughts,

John

[Al_The_Man]

The 510 overtravel is a stored stroke over travel, IOW it is a soft overtravel, the other is a hard overtravel because you have it a hard wired limit switch and tripped the E-stop input.
You can cancel the stored stroke limits by pushing P & Cancel button while powering up until the normal screen comes up.
In the 700 parameters there is the value for the stored stroke limits, you can put the maximum + & - distance in them so the strok is ignored if you wish.
Al.

[John3]

Thanks for the help!

It seems that I'm better off with the stored stroke limit instead of the hard limit switch?

When I "bump against" the stroke limit, the machine is fine, just needs a reset. When I hit the limit switch, all sorts of stuff is lost and must be reset.

Sounds like my problem is that the stroke limit is set on the wrong side of the limit switch. I need to have the stroke limit reached before the hard limit switch.

Am I seeing this correctly?

John

[Al_The_Man]

Yes this is one of the reasons for the soft limit, there are parameters to set it up including wether it is looked at, at power up, before home or after.
Do you have the manuals?
Al.

[John3]

Al, thanks again!

I don't have the actual manual for the particular machine and control (Fanuc 0-T) but I do have portions of manuals that come close.

The ball screws are metric, machine coordinate dimensions are mm. The machine would trip out the limit switch (E-Stop?) relay at X=-6.355 mm. The X- soft limit in parameter #704 was set to -8000. I changed it to -6000 and that fixed the problem sometimes. I changed it again to -5000 and now its all better.

This brings up a bigger question. This 6-axis lathe is in good mechanical and electrical shape, but its been "abused" over the years by people screwing with the limit switch dogs and I presume some of the limit and offset parameters.

For instance, this machine has another annoying problem. If the rear spindle Z axis is sitting near home and you do a Zero-Return, the machine trips out with a Z- over travel. If you first move the rear spindle Z to mid travel, the Zero-Return works fine.

What would the procedure be if I wanted to redo this stuff and make it right. For instance I think first I need to find the actual limits of the mechanical travel. Then after that how and in what order do I do; setting the travel limit switches, setting the home/deacceleration switches, setting the grid shift values, the soft limits, the zero-return parameters, the X-axis turret mirror value and anything else I'm forgetting or don't know about?

John