THREAD CHATTER

[mousongie]

Hi !

Im having a CHATTER problem when cutting metric thread (M24x2) on my Cnc lathe KIA TURN with fanuc controls.
In fact im machining a steel but its happens that my thread are comming out with terrible chatter.

Here is the overview of the program;

N4(Thread M26x2)
G40G0T0303;
G97S400M3;
G0X25.Z10.M08;
G01Z6.161;
G71P000030 Q250 R30;
G76X21.546 Z-20. P1227 Q280 R0 F2.0

[quocknguyen]

if you have problem with thread chatter when you put in new insert..... turn off coolant and run one or two parts.... dont extend the part out too long from the jaw......i used to run thread everyday.

[SumDumPhuckr]

Since you can not increase the feed, Reduce the speed

[dcoupar]

You did mean to put G76 (not G71) in the first block of the cycle, right?

G71P000030 Q250 R30

I don't work in metric, but it looks to me like the Q (min depth of cut) in the first block is 0.25mm which is 0.0098. These are pretty heavy cuts at the bottom of the thread.

Also, your tool angle is 30, which I believe results in a 15 degree infeed, which may be a little steep. Have you tried 60 or 55 degrees?

Lastly, you're not taking any "spring passes". Don't know if that would help or not.

[sinha_nsit]

R should be in mm in the first block:
G76 P030060 Q100 R.03 (if you mean 30 microns)

[dcoupar]

Originally Posted by sinha_nsit R should be in mm in the first block: G76 P030060 Q100 R.03 (if you mean 30 microns)

Pardon my ignorance, but in mm, isn't R.03 the same as R30? In inch mode, the two values would be different, but as there's 3 decimal places to the right (nnnnn.nnn) in mm, R30 would be .030?

Inch Mode (nnnn.nnnn):

R0.03 = 0.0300
R30 = 0.0030

MM Mode (nnnnn.nnn):

R0.03 = 0.030
R30 = 0.030

[sinha_nsit]

Trailing zeroes can be omitted. So, R.030 is same as R.03
Whether R30 would be 30 microns or 30 mm, might depend on 3401#0.
Did I understand your question correctly?

What you have said is correct.

[dcoupar]

Originally Posted by sinha_nsit Trailing zeroes can be omitted. So, R.030 is same as R.03 Whether R30 would be 30 microns or 30 mm, might depend on 3401#0. Did I understand your question correctly? What you have said is correct.

Yes, I know that trailing zeroes can be omitted. I included them in my example for clarity.