Need help with ringing/chatter on turned part

We have a part that we are trying to move from manual to CNC Lathe.

See Picture.

> Part: Faceplate welded to shaft. 2-300/year, OEM
> Operation in question is final OP. We are finish facing the plate and finishing the counter bore. Usually the issue is ringing/chatter on the 2 faces. Sometimes the part is out of tolerance.
> Gripping on shaft with pie jaws. Using the pie jaws we have tried to also grip the OD, we have tried to grip the OD with rubber inserts-varied pressures with thickness changes. We tried putting rubber between part and jaws, tried ring on back of faceplate (bolted to threaded holes) Thinking must grip on shaft to hold tolerances
> Tolerances runout 0.002" perpendicular 0.003" over 14" - not an issue manually
> Checking parts with CMM
> Running manually the operators used a stick to stop ringing

Please feel free to ask questions!!
Edits:
Answers here;
> Machine HAAS ST-35Y 2015, Tooling Facing tool Walter WNMG080406-NM4 with breaker, Jaw pressure 100-150, Cutting speeds/feed 214 ramps to 400 (I did not know it was this low??) Programed feed 12.

looking into: Setting 165 value is 50,setting 166 value is 20
At 2" diameter the CSS happens to be lets say 2500 RPM
setting 165 will speed the chuck up to 2550 then down to 2450 RPM at 2 seconds per RPM change,if setting 166 value is 50 then it will change RPM every 5 seconds.
The control will not read this code in tapping mode but will in G92 or 76 though they recommend against it.

First used it today on a long bore that was giving me crap with chatter,once I figured out how to use it man it was the best thing after sliced bread.

Your part fixturing with pie jaws sounds rigid and should keep the workpiece round. I'd prefer clamping on OD of the flange, but if you must use the shaft for locating the turned features, then it's the place to clamp the workpiece.

What kind of tooling do you use for the turning operation? What kind of cutting speeds and feeds do you use for roughing and finishing? What kind of machine?

Answers in original post

desim said:

We have a part that we are trying to move from manual to CNC Lathe.

See Picture.

> Part: Faceplate welded to shaft. 2-300/year, OEM
> Operation in question is final OP. We are finish facing the plate and finishing the counter bore. Usually the issue is ringing/chatter on the 2 faces. Sometimes the part is out of tolerance.
> Gripping on shaft with pie jaws. Using the pie jaws we have tried to also grip the OD, we have tried to grip the OD with rubber inserts-varied pressures with thickness changes. We tried putting rubber between part and jaws, tried ring on back of faceplate (bolted to threaded holes) Thinking must grip on shaft to hold tolerances
> Tolerances runout 0.002" perpendicular 0.003" over 14" - not an issue manually
> Checking parts with CMM
> Running manually the operators used a stick to stop ringing

Please feel free to ask questions!!
Edits:
Answers here;
> Machine HAAS ST-35Y 2015, Tooling Facing tool Walter WNMG080406-NM4 with breaker, Jaw pressure 100-150, Cutting speeds/feed 214 ramps to 400 (I did not know it was this low??) Programed feed 12.
Mark

Click to expand...

Ok, so it sounds like you are getting a major problem with resonance especially when gripping the work on the shaft. On manual lathe the 'stick' method tends to dampen the vibration - correct? So how do you dampen (or de-vibrate) the set-up when running in the cnc lathe?

Well, you have a bunch of threaded holes on that large flange/plate, the front face is being machined, but what about the back face? If that is not being machined then maybe you could make up something like a 1" thick slave plate from some sort of plastic like nylon or acetal, screw it on to the back face with the holes that are already there, then try machining the assembly with the plastic plate attached and see if that dampens the vibrations out enough. Otherwise drastically reduce your cutting speeds, and go to a cutter with a sharper tip geometry, uncoated if necessary.

If the 1" plastic plate idea works you may just have to make a few of them if you are running production, to give an operator time to swap the dampener out onto next parts.

Cheers, Dean.

Haas has a function that will allow you to oscillate (perhaps not the right word) the rpm up and down automatically in order to disrupt the resonance. Cant remember what it is offhand. Will try to find it and get back.

Maybe try a cutter with a smaller tool nose radius and see if that helps. I find the larger the radius the more it likes to sing.

Gobo said:

Haas has a function that will allow you to oscillate (perhaps not the right word) the rpm up and down automatically in order to disrupt the resonance. Cant remember what it is offhand. Will try to find it and get back.

Click to expand...

M38 turns on the SSV function. It has been a while since I used it, if I remember correctly a parameter setting (cant remember which one) increases and decreases by a given percentage your programmed spindle speed. This should help disrupt any resonance. A smaller nose radius combined with a positive rake cutting edge will reduce cutting pressure.Go to the Haas forum. There may be detailed info on the SSV function.

think I would a few different geometry choices perhaps to direct the cutting forces more toward the center and perhaps a different radius. You may fund a less-chatter insert but may sacrifice a bit of tool life (or not).
Don’t know if you stated part material but might try a geometry for a different material.

Building on Kiwi's suggestion: a plate of lead bolted to the back of the flange will probably kill the resonance.

Bolt the whole thing to a 2-4" thick disc of cast iron.
Ringing gone.

Its well within spindle mass allowance (do check).

Optionally, use lead inside a thin-skin CI/steel faceplate.

Ideally, imo, ime, dampener mass is several times workpiece mass.

You can't do this at lathe speeds but for long and chatter jobs in grinding we would put on, or wrap on a slug of children's modeling clay. That made chattery parts run dead solid.

For the time needed to put on and take off weights, playing with geometry and sharpness would be a possible choice.
Sometimes the force to penetrate the material builds up to the needed amount and then the break away can set up a harmonic and cause chatter. Cast iron and harder steel are very common to do this as they often fracture rather than flow. The angle of the shear force can sometimes direct the force in a more favorable way. Some time pos/neg mill cutters do this with having an axial attitude one way and radial the other.

[we are trying to move from manual to CNC Lathe} are the tool holder as hefty on the CNC?

Just a thought...

With a bit of double sided tape, apply some soft rubber material to the front of your pie jaws.

Leave the last 1" or so from OD of part rubber free on the jaws.

Fab up a "C" shaped gauge to set distance from back of part to face of jaw that the operator will have to apply a moderate amount of pressure to to give some crush onto the rubber when shoved against the "C" gauge (gage?).
Using the gauge will serve two purposes. one is to maintain a consistent length for your G54 and to load against the rubber which should dampen the vibration.

PS...Strips of electric tape under your boring bar holders work wonders if your using the BOT turret. Used to use a 2012 HAA ST-30, helped loads with chatter issues, does not effect accuracy of machine.

Use a diffrent insert - something sharper and take a lighter finishing cut. IME chip breakers are a key source of resonance on parts like this, to break the chip they oftern increase the thrust on the part, then the chip breaks releasing that pressure, get a flexable part with the correct resonance and you have chatter galore! Switch to a stainless style finishing insert that’s sharper and it generally solves the problem for me!