Threading Issue Cincinnati HTC-250

JT22 · Apr 11, 2016

New to the forum and I've found this site very useful for years. First off I'm not a programmer by trade but have been thrown into the role since our engineers at my workplace don't contribute much in this aspect of my job in Maintenance and we don't have a cam program for our cnc lathes. We have a pretty extensive set of duties here including full machining, electrical, repair, building etc. You name it we have to have some knowledge in it.

I've read every post here concerning G76 code programming for my machine which has a Fanuc 21i-TB control. I'll list the program and what it does. I'm trying to turn 1/2-20 threads and I have self taught myself on this machine so far. It's done everything I've programed with other repetitive canned cycles but just won't thread on this portion . Here's what I've got in the part of the program where it stops on 2nd line of G76 and just sits there doing nothing:

N340 T0909
N350 G97 S800 M04
N360 G0 X.550
N370 G76 P020060 Q0050 R.0005
N380 G76 X.404 Z-.90 P0100 Q0472 F.0769
N390 G1X5.0 F.150
N400 M30

It just seems like the machine is waiting for more information as it sits at the starting point of where the threading starts. In running the simulation it appears to only run 2 passes in the threading portion but it does show it threading. Everything else in this program works fine.

Any input or help would be greatly appreciated as I've exhausted every means. Thanks again for this great site!

JT

yardbird · Apr 11, 2016

20 threads per inch .0769? More like 50 but I'd think it'd still run?

P is the thread height Q is the first depth of cut. Try swapping them numbers and try it again?

Also I'd give it a Z.5 on N360. Obviously M4 isn't backwards spindle rotation?

Brent

JT22 · Apr 12, 2016

Correct, my feed rate should be .05. I'm going to try your suggestion right now. Thank you!

JT22 · Apr 12, 2016

I corrected the feed rate and changed line 360. Still just feeding down to .404 dimension on 2nd line of G76 command and sitting there. I have this now:

N360 G0 X.550Z.500
N370 G76 P020060 Q0050 R.0005
N380 G76 X.404 Z-.90 P0100 Q0472 F.05

Possibly you meant switch the order of P and Q and put Q first in order of how i write them?

angelw · Apr 12, 2016

JT22 said:
I corrected the feed rate and changed line 360. Still just feeding down to .404 dimension on 2nd line of G76 command and sitting there. I have this now:

N360 G0 X.550Z.500
N370 G76 P020060 Q0050 R.0005
N380 G76 X.404 Z-.90 P0100 Q0472 F.05

Possibly you meant switch the order of P and Q and put Q first in order of how i write them?

P should be 0472 (Thread form height, Q should 0100 (DOC first cut).

Ensure that the control is in Feed Per Revolution Mode by executing G99 prior to the Threading Cycle.

Regards,

Bill

sinha · Apr 12, 2016

angelw said:
Ensure that the control is in Feed Per Revolution Mode by executing G99 prior to the Threading Cycle.

Regards,

Bill

Bill,
The manual says that F is Lead. It does not describe it as feedrate. Therefore, I believe, G98/G99 have no effect on threading cycles on a lathe???

Sinha

angelw · Apr 12, 2016

sinha said:
Bill,
The manual says that F is Lead. It does not describe it as feedrate. Therefore, I believe, G98/G99 have no effect on threading cycles on a lathe???

Sinha

Hello Sinha,
See below the Screen Shot extract from manual. G76 with regards to Feeds follow the same rules as G32.

Unless the OP specifying the Thread Depth 1st Pass (Q) being greater than the Thread Height (P) is confusing the control, there is nothing else in the OP's code listing that would cause the G76 cycle to stop, other than a Feed Per Minute Feed Rate being so slow that the cycle appears to have stopped.

To JT22
Run your current program again and when the Threading Cycle appears to have stopped, change to a Coordinate Position Page and observe if there is any change in the Z axis display.

Regards,

Bill

sinha · Apr 12, 2016

Bill,
I tested G76 with both G98 and G99 on Fanuc NCGuide. There was no difference. In both cases, the "actual feed" (ACT. F) displayed the same value (in mm/min).

Sinha

Ox · Apr 12, 2016

N340 T0909
N350 G97 S800 M03
N360 G0 X.550 Z.5
N370 G76 P020060 Q0050 R0005 (I never use decimal here, but book doesn't say that it's not OK)
N380 G76 X.435 Z-.90 P0315 Q0119 F.05
N390 G0 X5.0
N400 M30

Personally, I would make the first line look like:
G76 P010160 Q0010 R0010
A min depth of .005 is a lot of cut in and of it'self, but I'm not sure how the control would interpret that with a .0005 finish pass? But what we have up top may function. Or maybe that is what it's tryin' to figger out???

I thread in G98 on a Fanuc all day long. 16, 18, 18T. No worries...

These will help you:

G76%20Cheat%20Sheet%20001_zpsw4h7t7mx.jpg

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I am Ox and I approve this h'yah post!

JT22 · Apr 12, 2016

Hey guys thanks for the input so far. I have taken all information given so far. Here's what I have modified in the program with your given information:

N340 T0909
N350 G99 G97 S800 M03
N360 G0 X.550 Z.5
N370 G76 P010160 Q0010 R0010
N380 G76 X.435 Z-.90 P0315 Q0119 F.05
N390 G0X5.0
N400 M30

Ran program...same results. Machine gets in starting position at X.550 and Z .5, feeds down to X.435 dimension in 2nd line of G76 and just sits there. Won't continue further. This is frustrating to say the least. Can't remember ever having an issue like this while learning how to program. Anything?

HuFlungDung · Apr 12, 2016

Try having the minimum depth of cut greater than the finish cuts, not equal. Ox wrote this above. I'd probably take a couple of .001" cuts to finish, so I'd spec a minimum depth of cut of .004 or so, there is no use dragging the tool along on the surface too many times with barely cutting anything.

sinha · Apr 13, 2016

Try R0.001 in N370

angelw · Apr 13, 2016

JT22 said:
Hey guys thanks for the input so far. I have taken all information given so far. Here's what I have modified in the program with your given information:

N340 T0909
N350 G99 G97 S800 M03
N360 G0 X.550 Z.5
N370 G76 P010160 Q0010 R0010
N380 G76 X.435 Z-.90 P0315 Q0119 F.05
N390 G0X5.0
N400 M30

Ran program...same results. Machine gets in starting position at X.550 and Z .5, feeds down to X.435 dimension in 2nd line of G76 and just sits there. Won't continue further. This is frustrating to say the least. Can't remember ever having an issue like this while learning how to program. Anything?

Hello JT22,
Take a look at Parameter 0001, Bit 1; this is the second bit from the right. The control may be set to FS15 Format and is not understanding the arguments specified in your Two Block Format. If Parameter Bit 0001.1 is set to "1", then the control is set to FS15 Format. FS16 Standard Format is set with a "0" in Parameter Bit 0001.1

Regards,

Bill

Ox · Apr 13, 2016

I'm bett'n on the param issue as well at this point.

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

I am Ox and I approve this h'yah post!

JT22 · Apr 13, 2016

Parameter 0001.1 is set to '0'. Still same issue.

Ox · Apr 13, 2016

This is just a single turret machine - right?

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

I am Ox and I approve this h'yah post!

Ox · Apr 13, 2016

Have you ran any code in G99 on this machine?

I don't know if the threading would pick up on the same encoder as the G99 would?

I take it that you are on 3rd shift eh?

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

I am Ox and I approve this h'yah post!

yardbird · Apr 13, 2016

Try going out 6 places on the Feed? This sumbitch ought to be running? If the cycle didn't ignore the feed override I'd suggest taking it of zero. wtf? Try kicking it?

Brent

Ox · Apr 13, 2016

The fact that it is feeding down to the X.435 dimmension tells me that it is not reading the code correctly. It should only feed to prox X.475 on the first pass. So it seems more like a param or macro issue to me.

Just dbl checking, but you know that bit "0" is all the way to the right eh?

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I am Ox and I approve this h'yah post!

JT22 · Apr 13, 2016

Yes, single turret.

Threading Issue Cincinnati HTC-250

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