Need help! Fanuc oi-td g76 taking entire depth in one cut.

Here's what I've got.
G76 P030060 Q20 R20;
G76 X2.588 Z-2.5 R0 P081 Q180 F.125;
I can't figure out why it immediately plunges in to the entire depth.

Peewee_750 said:

Here's what I've got.
G76 P030060 Q20 R20;
G76 X2.588 Z-2.5 R0 P081 Q180 F.125;
I can't figure out why it immediately plunges in to the entire depth.

Click to expand...

Hello Peewee,
In your second G76 Block, you have specified a Thread Height of only 0.0081 (P081) and a First Pass DOC of 0.0180 (Q180). Accordingly, its not surprising that the tool goes to full depth.

Given the specified Lead (F0.125) and X coordinate (assuming its an External Thread), I suspect that the Thread Major Diameter is 2.75". That being so, the P value should be 0.081. When the period is omitted from the value, the specified value represents a number of Least Programmable Increments. As it appears that your program is using imperial values, the program as is would be specifying 81 x 0.0001 units for the Thread Height (0.0081) and 180 x 0.0001 units for the First DOC (0.018). Accordingly, the control would calculate a First Pass X coordinate of 2.5682". As the control will not go to a value less than the specified X value in the second G76 Block, the First Threading Pass would be at 2.588".

Your P value should be P810 and your Q value of Q180 will work.



Regards,

Bill

Well, I just figured out that I needed another digit in the single side depth.

I went back through the o list, found another program that cut 8 tpi and the P value was P0811. I changed my P081 to P0811 and it straightened right up.

Thank you Bill.

Peewee_750 said:

I went back through the o list, found another program that cut 8 tpi and the P value was P0811. I changed my P081 to P0811 and it straightened right up.

Click to expand...

Hello Peewee,
When the period is omitted, the Leading Zeros are not required, only the Trailing Zeros are important. Think of it in terms of the number of Least Programmable Increments and specify that value. P0810 and P810 are equal.

Regards,

Bill

Peewee_750 said:

Here's what I've got.
G76 P030060 Q20 R20;
G76 X2.588 Z-2.5 R0 P081 Q180 F.125;
I can't figure out why it immediately plunges in to the entire depth.

Click to expand...

It took one single pass at full depth? Or did it jump to full depth and take two passes at the exact same depth? I spent a fair amount of time trying to make the 2 line G76 cycle take one single pass at full depth. I never was able to make it happen. Lol...

Brent

angelw said:

Hello Peewee,
When the period is omitted, the Leading Zeros are not required, only the Trailing Zeros are important. Think of it in terms of the number of Least Programmable Increments and specify that value. P0810 and P810 are equal.

Regards,

Bill

Click to expand...

Gotcha! Thank you for clarifying.

yardbird said:

It took one single pass at full depth? Or did it jump to full depth and take two passes at the exact same depth? I spent a fair amount of time trying to make the 2 line G76 cycle take one single pass at full depth. I never was able to make it happen. Lol...

Brent

Click to expand...

It jumped in just a few thou. over final depth. It got about 1/4" across the part before I stopped the machine. I didn't let it complete the first pass.

Peewee_750 said:

It jumped in just a few thou. over final depth. It got about 1/4" across the part before I stopped the machine. I didn't let it complete the first pass.

Click to expand...

Oh! Yeah I bet you did! I don't know why I didn't make the connection you were actually going to full depth on a part. Good on you for getting it shut down in a hurry. That kinda shit'll drive me back to drinking. Lol...

Brent

yardbird said:

Oh! Yeah I bet you did! I don't know why I didn't make the connection you were actually going to full depth on a part. Good on you for getting it shut down in a hurry. That kinda shit'll drive me back to drinking. Lol...

Brent

Click to expand...

Yes, indeed. It was enough to turn my stomach. Its the only part I have to run and I'd hate to have to weld it up. Lol.