G78-NEED HELP PLEASE

[CHANDRU]

Friends,

Recently after commissioning a cnc with oi-TC controller we had G78 Threading cycle problem.

While machining after few passes the spindle was stopping and the tips were breaking.Later we found that there was some G-CODE missing in the program like G90,G53 and G97.

Following is the G78 threading cycle program.

Any mistake pl identify them.

G90 G53 T0505:
G97 S500 M04:
G0 X135.0 Z20.0:
G0 Z5.0 M07:
G01 Z20.0 F1.0:
G78 X132.6 Z-25.0 F4.233:
X132.4:
X132.2:
X132.0:
X131.8:
X131.6:
X131.4:
X131.2:
X131.0:
X130.8:
X130.6:
X130.4:
X130.2:
X130.0:
LIKE THAT
UP TO X128
AND FROM X128.0
X127.95:
X127.9:
X127.85:
X127.8:
X127.767:
G0 Z20.0 M09:
T0000
G0 X0 Z110.0 M05:
M01:

Similarly while doing internal threading cycle with g78 after few passes the tool is digging.

IAM NOT FAMILIAR WITH PROGRAMMING SO PL HELP ME.

Thanks

CHANDRU

[dcoupar]

First of all, I assume that parameter 3401 bit 7 = 0 and bit 6 = 1, correct? (G-code system B)

I don't see anything wrong with the program except maybe you could insert a G95 (Feed Per Revolution) for safety.

When the spindle stops is the insert in the cut? Are there any alarms when this occurs?

[CHANDRU]

Dear decoupar,

YOU ARE WRIGHT AND THE PARAMETER 3401 BIT 6 IS 1.

COULD YOU PL TELL ME WHERE EXACTLY WE HAVE TO INSERT THE G95 CODE.

THANKS,

CHANDRU

[dcoupar]

In with the G97 block would be fine. You didn't answer my question about where the spindle is stalling and if there are alarms.

[CHANDRU]

Dear dcoupar,

The spinle is stalling after few passes and that too while doing initial setting.Suppose we are not getting the proper thread form after the completion of the cycle and when we give 0.3 or 0.5 cut more depending on the appearance/requiremnt of the thread the tool after passing few threads a digging like sound is coming and we are getting the following alarm.

The spindle alarm no is 9031 and as such the encoder cable is thoroughly checked and the related parameters like 4002 bit 1,0 are(10) and the parameter 4005 Bit 0 is 1.

Thanks

CHANDRU

[dcoupar]

9031 sounds like the spindle is stalling. Does your machine have a gearbox? If so, try running the thread in low gear.

[CHANDRU]

Thanks dcoupar,

The machine is nothaving a gear box.




CHANDRU

[dcoupar]

Have you watched the load meter during the cuts? Does the machine have a dual winding motor? What make/model of machine is it?

[CHANDRU]

Dear dcoupar,

The cycle works fine with components having dia of less than 100mm but when the dia increases above 100mm this problem is occuring.

Should we go for G92 instead of G78

We donot want to leave the problem as it is without solving

The spindle motor is Beta6-8000 series

Thanks,

CHANDRU

[dcoupar]

I'll repeat my question: What make/model of machine is it?

[CHANDRU]

Dear decoupar,

The machine is an INDIAN MAKE and the controller is FANUC 0i-TC


Thanks,

CHANDRU

[dcoupar]

G92 on your control is not a threading cycle. It's coordinate system setting or max speed setting.

You might try a G76 cycle with an infeed angle of 30 degrees the tool will cut on the leading edge only, and this might reduce the load enough to avoid stalling the spindle.