[Dave Wojo]

Hello,

I am new to this forum and hoping someone can shed a little light on the g76 one line thread cycle. Most of our machines use the two line, but on this one particularly old one I do not have that capability.

The issue I am having is "chatter" in my threads.

I am running a really hard cast malleable iron. I've tried multiple attempted solutions but no consistency has been achieved.

My Current thread line looks like this: (creating a 2-11.5 npt external thread)

G76 X2.269 Z-1.12 K0.07 I-.044 D280 F0.08696 A60

I have read that if you add a P to this it will allow different infeed methods, but I honestly have no clue what that means. On the dual g76 lines I would just adjust the first line to adjust the finish depth of cut's. Is there Would changing the thread flank angle or the infeed help in this situation?

Thanks for your help,
Dave

[fordav11]

P is a later addition to the G76 command on Fanuc 15-series controls.
It is still available on later controls but first you must set a parameter to Fanuc 15-series style cycles then use the single line coding for cycles.
Parameter 0001 bit 1 (FCV) =1 for Fanuc 15-series format (1 line cycles)
FCV = 0 for Fanuc 16 series format (2 line cycles)
if your machine can do it you can do 4 types of in-feed.
see the attached for details.
I have not really noticed a difference with problem threading with using P. I normally have to either use a slower speed or more rigid tool, or do the job on a more rigid machine.

[Dave Wojo]

I tried all 4 types of P and your correct, it didn't change much at all. I think I will modify my workholding a little to try to get less overhang on my part. But I really do not have much more room to work with. Oddly, a slower speed it causing more chatter. And additional passes is causing more chatter as well.

The only luck I am having is to ramp the RPM's up to a high rate with very few passes. Though, that is causing my tool life to decrease dramatically (we run 5000 pc's per batch). I've tried multiple inserts including different chip breakers. I am just boggled to what else I can do to reduce the chatter.

[fordav11]

can you take a photo of your set-up with a part in the machine and post it here? unless you are cutting a thread that is 1/2" deep you shouldn't have chatter. another trick is to run the tool slightly below center. if your tool is upside-down then above center. pack the tool up/down only by about 0.010"-0.020" using shim or similar.

[ceh007]

Check the CNC handbook, tells all.

[harshal]

Check the CNC handbook, tells all.

http://www.hdknowledge.com/2018/07/g...scription.html
N10 M06 T01 01 ;
N20 M04 G97 S1000 ;
N30 G00 X45 Z5 ;
N40 G76 P020060 Q100 R50 ;
N50 G76 X38.7 Z-50 P1227 Q100 F2 ;
N60 G00 X45 Z5 ;
N70 M05 M09 M30 ;

DESCRIPTION OF MAIN PROGRAM :-

N10- Tool change command , select tool no. 1
N20- Spindle ON anti clockwise , constant spindle speed command , speed is 1000 rpm
N30- Rapid action command where X45 and Z5 .
N40- Threading cycle command , P020060
( P02 = No. of finished path
00 = Chamfer amount at end
60 = Angle of tool tip ) ,
Q100 = Each cut is 0.1 mm ,
R20 = finishing allowance 0.02mm
N50- Threading cycle command , Minor dia X axis , threading along Z- axis up to -50 , Threading depth , Depth of finish cut 0.1 mm , pitch is 2 .

: M40X2

Major diameter is 40
Pitch is 2
Thread depth calculation = Pitch x 0.61363
= 2 x 0.61363
= 1.227 mm in micron is 1227

Minor diameter = 40-1.23 = 38.7 mm

N60- Rapid action command where X45 and Z5 .
N70- Spindle off , coolant off , main program end .
for more info visit - www.hdknowledge.com

[harshal]

G76 FANUC TAPER THREADING CYCLE EXAMPLE
July 24, 2018
Jabong CPA IN


01542
N10 M06 T03 03 ;
N20 M04 G97 S1000 ;
N30 M08 ;
N40 G00 X50 Z2 ;
N50 G76 P010060 Q100 R50 ;
N60 G76 X45 Z-55 P1227 Q200 R10.5 F2 ;
N70 G00 X50 Z2 ;
N80 M05 M09 M30 ;

DESCRIPTION OF PROGRAM :-

Starting calculation please click here
01421- Name of program
N10- Tool change command , select tool no. 3
N30- Coolant ON
N20- Spindle ON anti-clockwise ( for RH thread) , constant speed command , speed is 1000 rpm
N40- Rapid action command , where X50 and Z2
N50- Threading cycle command , P01 - no of finish path
00 - chamfer amount is 00mm
60- angle of tool tip ,
Q100- each cut is 0.1 mm ,
R20- finishing allowance 0.02 mm
N60- Threading cycle command , X45 is end diameter , tool threading upto -55 in Z axis , P thread depth 1.227mm , depth of finish cut is 0.2 mm , R taper thread parameter is 10.5 , F is pitch is 2.

P Depth of thread = pitch x 0.6136 = 2 X 0.6136 = 1.227 mm = 1227 in micron
R taper thread parameter = ( end dia. - start dia ) / 2 = (45-24) / 2 = 10.5

N70- Rapid action command , where X50 and Z2
N80- Spindle OFF , coolant OFF , main prog. end .
for more info - visit ----
www.hdknowledge.com