Fanuc 3m Contol, Morton Mill, X overtravel alarm

[brgrii]

1. I recently purchased this old non-working mill, installed a new Power supply and - wah-la it works (mostly). Everything seems to be fine except the x axis indicates an overtravel in +x just past what should be the mid point of travel. In the minus direction it will travel all the way to the limit switch. I scoured the manual and find parameters 0070 -0075 seem to be a software limit of travel settting. The settings are 11000, 21500, 6700, -695000, -370000, and -137000. The seem a bit odd. Dare I change these settings? Is something possibly broken in the mechanics? Any ideas?

2. I have the Fanuc 3m-C manuals, but nothing for the mill itself - anyone know where I can get a manual for this old Morton (1985)? I can't find anything on the web about the Morton Machine company.

Thanks for any help!

[Al_The_Man]

Originally Posted by brgrii 1. wah-la it works (mostly). Everything seems to be fine except the x axis indicates an overtravel in +x just past what should be the mid point of travel. In the minus direction it will travel all the way to the limit switch.

wah-la (voilá)
Most Fanucs have a button sequence on power up to get rid of software overtravels, I am not sure if this is valid for the 3M but here it is:

Power off the control and before you power it on again the push and
hold at the same time the letter "P" and the "cancel"button then power up
the control, hold down the two buttons until the control powers up
completly. Perform home routine.
Al.

[Dan Fritz]

The Fanuc 3M is a lot like the 6M, only it has limited memory and no parallel tape reader port. I'm very familiar with these controls, but I don't have a manual on the 3M, so I can't help you with the parameters.

The "software" overtravel limits are called "stored stroke limits", and there should be two different kinds of limits on this control. One kind is used for simple overtravel protection, and these software limits are usualy set just inside the boundaries of the hardware overtravel switches. I don't have a 3M manual, but there should be a set of parameters for +X, +Y and +Z, then another set for -X, -Y and -Z. These distances are programmed in "Detect units", which are probably metric (.001mm) if your machine has metric ball screws. The numbers are the distance from the zero-return point to the limit. The software overtravel limits are not effective until you zero return the machine the first time after power up. One thing about these software limits is that they are "look-ahead", which means that the CNC will alarm out if you just PROGRAM the machine to exceed a limit. If you are in the middle of your table travel and you program a move that would exceed a limit, the CNC will alarm out BEFORE the machine makes the move. That means that it's possible to get the alarm without actually coming near the limit.

Another set of software travel limits were sometimes used to set a 3D "box" that the machine could not enter. I seem to recall that this was called "stored stroke limit 2", or something like that. This feature was intended to protect your vise, your fixture, your chuck (on a lathe), etc. There is also a parameter that makes this "box" either "inside" or "outside". If it's set to "outside", then the tool can't enter this box. If it's set to "inside", then the tool can't go OUTSIDE this box.

When adjusting the hardware switches for overtravel or adjusting the zero return switches, we would always put big numbers (positive and negative) in these parameters. We'd put "99999999" in the positive limits and "-99999999" in the negative limit parameters. Then, the software limits would never be triggered and we could do other service related work. There's no harm in doing this, but if your machine needs the software overtravel limits, it would be wise to set these parameters back to their original settings afterwards. There should be at least TWO methods for preventing a crash at the end of your machine's travel. Most machines use a hardware overtravel switch and a SECOND overtravel switch that puts the control into E-stop. That way, if one switch should fail .....

The software overtravel limits were used on many machines to save the trouble of mounting two sets of overtravel switches. They work fine ...if they're programmed correctly, of course.

Al_The_Man is correct that many Fanucs have a key sequence to disable the software OT alarms, but I don't think that the Fanuc 3 or the Fanuc 6 ever had this feature. We always had to set the parameters to big numbers, or just turn off the software option to disable the limits. If there was a key sequence for this, they never told us about it.

Hope this info is helpful.

[brgrii]

Thanks guys ( I assume, I guess) - it worked. But now I do indeed have the concern Dan raises - I have only the one overetravel protection. When I performed the "P-cancel" trick, what happened? Did this reset some parameter so that I can now go back and check them against the list I input(ed? inputi?) to see what has changed? And if not, how do I get this protection back in and set correctly?
Thanks again! (I never realized voila was wah-la - I thought that was just a very small cello!)

[brgrii]

Opps, forgot another little problem. How DO I zero return this thing? I set the toggle to "ZRN", which I assume to be the zero return, and then jog the machine in X,Y, or Z. I then assume it will stop at this nebulus zero point, but it just keeps going until it trips the overtravel limit. Dang, I wish I had the Morton manual!

[brgrii]

Thanks - took a lot of goofing around with settings and fixing hard stops, but she now zeros and runs just fine.

[nestormc]

i`m looking for a fanuc 3m manual, can you send me a copy please, if you have it in archive.

[hrh]

Just for interest sake you can command G23 to disable the stored stroke limits before you zero return. This depends if your machine allows any MDI commands before zero return is completed.
G22 is modal and usually active upon power on. This enables stored stroke check.

[mechman5000]

My experience tells me to go to parameter 1815 and set apz to 0 then restart machine, run axis to 2nd limit then move back till 2nd limit isnt made then set parameter 1815 apz to 1 and restart . This action will set your new 0 position to just befoore the second limit and stroke limit should be fine.

[sderyck]

we have a fanuc 3m here, anybody know where I can get a programming manual?