[MotoDan]

Hello, I have a Fanuc 0-MC control on my Excel 520 VMC. My Z-axis machine limit is set such that I can't quite get the tool down to my work surface. Besides the limit switch (which I've bypassed with no luck in extending Z), how can I change the machine's Z limit? I only need to lower the limit by approx 1".

[jamesweed]

you have a stroke check1 soft limit that you will need to change. Its listed in the parameters. Tomorrow at work I can look to see which one(s) to change. I wouldn't think this soft limit would be set beyound the hard limit switch although??? Normally the soft limit is tripped before a hard wired limit switch. I'm thinking there are 3 stroke check limits avalible. 1 is used by machine builder, the other 2 are for operators' use. Isn't the hard wired limit switch there for a very good reason? I run a custom built mill so these limits were played with some in the beginning for me.

[RRL]

1.0000" is a lot! Mechanically you probably will not be able to do it without hitting something, such as a "bumper stop" on the ball screw, or something else. You need to look around the headstock and ball screw area to see if it is possible, and you may not be able to see everything.

I the past I have had customers looking to get .100 to .200" with no problems.

I either event the Z negative stroke limit parameter is 706. Make sure you record the original number to put back if needed. This is a metric value! You will need to add -2540 to the current value to get the 1" you say you need.

PLEASE USE EXTREME CAUTION!!!!! As I said you probably will not be able to get that much!

RRL

[MotoDan]

Thanks for your replies. I really appreciate your help.

I tried to gain access to the Z-axis ball screw, but was unable to. I did verify that there was plenty of room for the counterweight to move (quite a bit actually). I also measured the distance from the ways wiper to the end of the linear bearing which was 1.5". Definitely a limit I would not care to exceed.

The mechanical limit switch is set for about 0.3" beyond the soft limit, but could easily be moved a bit more without much trouble.

After looking over my fixture, it looks like I could get by with an additional 0.8" of Z travel, so it's not quite a bad as the 1" I originally was shooting for. Without seeing how close the nut is from the end of the ball screw, I have no way of knowing if I'm going to run into trouble by increasing the limit another 0.8".

I tried to look at parameter 706, but could not get to it. There's a gap in the parameter list, presumably to keep the uneducated from screwing things up! Should I decide to extend the soft limit, how do I get access to 706? Once changed, is the parameter saved in non-volatile memory or do I have to change the limit each time I power up the control?

As RRL said, it's in millimeters (from machine zero?), so if I wanted to extend the limit by 0.8" and my math is correct, I should add -2032mm to the existing limit.

Maybe I should just raise my fixture an inch and be done with it!

Thanks again for all of the advice.
MotoDan

[MotoDan]

Thanks to you guys I was able to make the parameter 706 change so that I could get another 0.8" stroke. I also made another limit switch cam which is set to shut down the machine if the stroke goes past the soft limit by approx 0.050". Everything seems to work fine. The soft limit is now exactly where I want it. Hopefully I'm not compromising the machine by doing this. The good thing is that no nasty sounds or binding occurred when I took it to the soft limit.

Once I had unlocked the parameter write bit, I was able to see P706. I then disabled any further writes and cycled power on the control and check the limit. It seems to be holding the new P706 limit just fine.

Thanks again for the great advice. You guys are a real asset to us all. Hopefully I can return the favor one day.

MotoDan

[Luslugger]

I get error 1002 soft limit 2, z axis is opposite zero end. I have about 17 in the work shift and the alarm comes at about 17.4 by the actual machine coordinates. I need to move .5 in the z minus direction. I can move the machine there with the handle. Where is this function set?

[Luslugger]

I have a leadwell lt15 ota and it has ussually been the same as a Mori Seiki