WTF???? Suddenly cutting undersized.

[alphonso]

Fanuc 0TC
Turning part.
Roughing tool brings diameter to 2.02".
Finish tool brings diameter to 2.00".
Did this 149 times.
17th part of the day, the finish tool cut to 1.944" instead of 2.0.

No changes to anything, just load, run, measure, load next part.

Run the next tool, finish tool for another section of part. Does not cut anything. Display shows desired diameter.

Now we are at WTF?

Manually bring first tool down to the 1.944 section and display says 1.944. Re-qualify tool and the X value in geometry table changed by .001. No wear offset for this tool.
Rerun the finish sequence. Display says X2.00, tool is skimming a smidge off the part at 1.944.

WTF????? What, other than encoder could cause this behavior?

Sprockets, belt and couplings all seem to be tight. AFAIK they have not been touched in 10+ years.

 

[nihilistic]

Maybe the tool slipped? Sometimes a birdsnest can cause weird behavior like that. Reseat, retighten and retouch.

Also restart the machine and re-zero the axes etc.

Double check work coordinates.

 

[alphonso]

No tool slippage. No change after power down/up.
Manually bring first tool down to the 1.944 section and display says 1.944. Re-qualify tool and the X value in geometry table changed by .001. No wear offset for this tool.
Rerun the finish sequence. Display says X2.00, tool is skimming a smidge off the part at 1.944.
Work shift unchanged.

 

[Ox]

Hot in your shop?

-------

Think Snow Eh!
Ox

 

[Ox]

Just fer grins, maybe edit the tool call-out from T101 to T113 and try that?


--------------------

Think Snow Eh!
Ox

 

[cnctoolcat]

Sounds like a wonky encoder...possibly heat related.
And since it is a Fanuc, make sure your tool is not picking up some erroneous TNR cutter comp...or comp'ing twice! It is important to properly cancel cutter comp/TNR for each tool after it finishes cutting.

ToolCat

 

[L C Svc]

Does your lathe us limit switches for ZRN ? If YES, try holding "P" and "CAN" keys while powering on. Hold the keys until machine comes ready.
Then ZRN both axis, This will reset zero position using the switches.

 

[alphonso]

Ox,
yes it is hot. 115. This machine is just inside an open 15 X 19 door with a 3 foot diameter squirrel cage fan blowing on it. Hadn't thought about calling a different comp.
LC,
Has limit switches. P CAN was one of the first things we tried. The home procedure seemed normal.
Toolcat,
Tool comp is canceled at every tool change just before the tool moves to toolchange position. Oddly enough, I was watching the screen and can verify that tool comp was off. Wondering about the encoder losing its mind.

 

[Ox]

Fanuc 0TC
Turning part.
Roughing tool brings diameter to 2.02".
Finish tool brings diameter to 2.00".
Did this 149 times.
17th part of the day, the finish tool cut to 1.944" instead of 2.0.

No changes to anything, just load, run, measure, load next part.

Run the next tool, finish tool for another section of part. Does not cut anything. Display shows desired diameter.

Now we are at WTF?

Manually bring first tool down to the 1.944 section and display says 1.944. Re-qualify tool and the X value in geometry table changed by .001. No wear offset for this tool.
Rerun the finish sequence. Display says X2.00, tool is skimming a smidge off the part at 1.944.

WTF????? What, other than encoder could cause this behavior?

Sprockets, belt and couplings all seem to be tight. AFAIK they have not been touched in 10+ years.

Can we make any sense of it with the math?

2 - 1.944 = .056
10mm pitch X screw (?) = .7874"D / rev
.7874 / .056 = 14.06
360* / 14.06 = 25.6*
That's a LONG ways in an encoder!

OK, I don't think that is gitt'n us anywhere.

-----------

I'm not sure exactly how to read the part in blue?
The tool is where it should be at that point, but not where it should be at the other point?
Or maybe it is not deep enough on the other point, while being too deep here?

Are all the other tools right where they're s'posed to be?
C/drills and drills all on C/L? (or there abouts?)
Would you know if a rougher was off .056?
Any other finishers?

If other tools are fine, and I'm guessing that they stick out further (well, maybe not the rougher(s)) a "punt" might be to pull this finisher out a bit further and see if your ghost stays or goes.


-------------------

Think Snow Eh!
Ox

 

[EmGo]

Has limit switches.

Could have picked up a chip.

 

[gmc1724]

Fanuc 0TC
Turning part.
Roughing tool brings diameter to 2.02".
Finish tool brings diameter to 2.00".
Did this 149 times.
17th part of the day, the finish tool cut to 1.944" instead of 2.0.

No changes to anything, just load, run, measure, load next part.

Run the next tool, finish tool for another section of part. Does not cut anything. Display shows desired diameter.

Now we are at WTF?

Manually bring first tool down to the 1.944 section and display says 1.944. Re-qualify tool and the X value in geometry table changed by .001. No wear offset for this tool.
Rerun the finish sequence. Display says X2.00, tool is skimming a smidge off the part at 1.944.

WTF????? What, other than encoder could cause this behavior?

Sprockets, belt and couplings all seem to be tight. AFAIK they have not been touched in 10+ years.

My Mazak would do this, turned out to be a loose grub screw on the encoder coupling, nipped it up and that was that.

 

[alphonso]

Can we make any sense of it with the math?

2 - 1.944 = .056
10mm pitch X screw (?) = .7874"D / rev
.7874 / .056 = 14.06
360* / 14.06 = 25.6*
That's a LONG ways in an encoder!

OK, I don't think that is gitt'n us anywhere.

-----------

I'm not sure exactly how to read the part in blue?
The tool is where it should be at that point, but not where it should be at the other point?
Or maybe it is not deep enough on the other point, while being too deep here?

Are all the other tools right where they're s'posed to be?
C/drills and drills all on C/L? (or there abouts?)
Would you know if a rougher was off .056?
Any other finishers?

If other tools are fine, and I'm guessing that they stick out further (well, maybe not the rougher(s)) a "punt" might be to pull this finisher out a bit further and see if your ghost stays or goes.


-------------------

Think Snow Eh!
Ox

Don't know how much the tool you highlighted was actually at, just know that it only cut air. Roughed diameter is 2.54, finish is 2.5. 2.5 is what displayed. Measured rough diameter after the finish tool didn't cut anything and it was the expected 2.54.
Did not check other tools to see where they are and think they are.

GMC1724,
Uses split collar rather than grub. Was really tight.

EG,
Didn't find a chip on the dogs.

 

[Ox]

Well, in your case, if your rough tool was U/S the same amount on feature B _ as the finish tool was on feature A, and the finish tool was correct on feature B, then it would be where you said.

Otherwise, the finish tool is +.040 on B, and -.040 on A.

Point is, is the issue effecting the rough tool as well, or is it effecting the finish tool in 2 different ways?


--------------------

Think Snow Eh!
Ox

 

[alphonso]

Both roughing tools seemed to cut correctly. Finish tool A cut undersize, finish tool B cut oversize.

 

[GENERALDISARRAY]

run a repeatability test for turret index positions.

 

[EmGo]

EG,
Didn't find a chip on the dogs.

Yup, it's almost never the easy stuff but you still have to look first. This is repeatable, it does it every time now or you quit after the first messup ?

 

[Bill in PA]

run a repeatability test for turret index positions.

I have had this happen. The teeth on the coupler would clash and get stuck with certain tools depending on how the turret was balanced (heavy tools on just one side of the turret). It would not do it all the time. It would affect the part shoulder locations and diameter. Added an optional stop at each tool change to see what was going on. I think my proximity switches need adjusted on the back of the turret.

Bill

 

[alphonso]

Haven't had time to get back to machine. Haven't messed with it since the quick check with the second tool. Ambient temp at machine is 112 F. Fuck it, I ain't gonna mess with it this afternoon.

 

[alphonso]

Able to spend a few minutes with the machine this afternoon. Touched off part with 4 tools and they all read some .056 smaller than actual size.
Temp is 114 F, Looks like I'll qualify 11 tools Monday morning and see what happens.

 

[alphonso]

Solution found. Programmer error. G41 instead of M41.