Fanuc 3T soft limits

Kenre · Dec 14, 2019

Had my first, and hopefully last big crash the other day.
Totally my fault, proving out a new program and to save time during code adjustments i started it part way through the program. A tool change, without going back to zero resulted in turret crashing into the chuck.

Tore a jaw clean off the chuck. Was going to purchase a new chuck in the near future anyway, it had plenty of wear in it.

Is there a way to change the Z axis limit so i can avoid this again. Turret does not need to go past the chuck in any of my work. By doing this the worst i could do is wreck a tool, much cheaper!

I could move the Hard limit switch but wonder if there is a better way.

yardbird · Dec 14, 2019

That Sucks! To avoid this again add a couple safety blocks to the start of each tool. If you have to stop it mid program flip the optional block delete switch to off. Once you've got it started put the block delete back to on.

/G28 U0
/G28 W0
/G0 U6.
/G0 W-10.
G50 X0 Z0
yadda
yadda

G0 X0 Z0
M30

When you've got the machine at wherever it is going to run orgin your relative U & W position then never start it without seeing double zeros on the CRT screen.

Bill can explain this much better than I can.

Brent

litlerob1 · Dec 14, 2019

I'm about 95% sure you can adjust the soft limits. I just don't know how. Point is-keep asking, Vancouver will know.

But in my experience, it doesn't matter. You can still crash Bars and Drills and shit into the Chuck. So best practice is learning from mistakes, use a safety protocol like Brent posted.

R

Vancbiker · Dec 14, 2019

Look at parameter 74. If your machine is set up to use soft limits that will be your Z negative limit from the machine zero return point. If your machine is built with metric screws (most likely) the units will be microns. If the machine has imperial screws, the units will most likely be .0001"

Dan from Oakland · Dec 14, 2019

Another approach- when proving out edited programs throw a minus Z work shift in and run through the program a given distance from your part. that way you can stop the program and check for interference at critical points. For me, and as stated above, there are just too many things that can cause a z crash other than relying on soft limits- jaw height, boring bar lengths etc. Oh- one more suggestion- turn your rapids down to 25% when you do your dry run.

Kenre · Dec 15, 2019

Thanks Vancbiker!
That was the one. Easily changed.

Yes i know it wont save me from crashes, id rather have a crash and just destroy a tool,and not the chuck like happened.

Tool change before crash X was retracted partially. Z was still up close to the chuck. No time to react, happened very quickly. Wiped out a tool holder and z kept on going until it hit the chuck.

With new Z limit only tool would hit, not the actual turret.
Amazingly turret was only knocked a couple of thou out. Just completed my 1st turret alignment.

Search

Largest Manufacturing Technology Community on the Web

Search

Fanuc 3T soft limits

Kenre

Cast Iron

yardbird

Titanium

litlerob1

Diamond

Vancbiker

Diamond

Dan from Oakland

Titanium

Kenre

Cast Iron

Similar threads