Chatter on small dia parts SL-30

[RickOmatic]

Ok, some quick information. I have been a machinist for over 30 yrs.(love having dirty hands...) Mostly manual, now in cnc mills and learning cnc lathes. Started with the Prototrak lathe and think it's great for what it is intended for. (quick and easy for 1/2/3 parts) Now I am working with a Haas SL-30 and running the same type of programing as the trak and getting terrible results! The machine was purchased used and had to be repared/serviced when it arrived. No visible damage, but I was told the headstock and turret were re-alligned. We tried a LOT of programing variations and it still comes out with chatter. Pretty sad that the other part shown below was cut on a machine half the size and not nearly as robust as the HAAS! Anybody have any thoughts? Dia of pics is .787 about 10.0 long
Headstock bearings/damage? Turret not locked solidly enough? Tailstock problems? (we tried changing the pressure a few times) I gotta get this figured out cause' this is way too cool not to play with, er, run ! Thanks for your time! Rick

[Geof]

I don't think headstock bearings or turret locking have anything to do with that chatter; if it was coming from either of these it would continue all the way up the the end near the chuck.

Try looking at the tool centering; a tool slightly above center, on a rear mounted tool it is below center when you look at it, will often chatter because as the work or tool deflects the cutter gets a litte bit deeper.

A tool slightly below center, again above for a rear tool, will sometimes cut much smoother.

[WOLOG]

Try switching tool geometry. I have problems like this sometimes. Using a cnmg-432 is not the best choice for a small diameter part such as this. You should use a positive geometry insert. Also try using a spring loaded center. i make similar parts and I mostly us VNMG-331's to relieve chatter. Also try changing the tool from a right hand/upside down to a left hand/right side up position. I find that pushing down on the ways are better for chatter than pulling away from the ways. Turret alignment will also give less than satisfactory results in surface finish. I don't care what anyone says, but there is a difference between a flat bed and a slant bed machine. i can do things on my TL-2 that causes problems on my SL-30 BB and the other way around. I know that this is a small part, but try an Iscar HeliTurn for roughing and such. It is an awesome tool. The insert is extremely free cutting and you can have large overhangs from the chuck and still od a part with no tailstock.

[RickOmatic]

Thanks for the input! I figured with all of the experience of the cnc zone guys I would get some good insite to my problem. I'll be trying out the fixes Monday. Thanks again for the help! Rick

[Five-10]

When I bought my first SL30 I also bought a high dollar Royal quad bearing cnc center. The first time we tried turning a long part we got chatter just like you. After trying everything from speeds feeds to hydraulic pressure in tailstock and chuck I told the operator to try the center off our manual lathe ( $80.00 Bison cheapo). Well the chatter was eliminated and Royal center was replaced with a new one. So I would make sure your center is good.

[ImanCarrot]

Also worth trying:

Rapid traverse the tool without the spindle running and stick your hand on the slideway to see if you can feel any vibration at the area where the "chatter" occurs. I had a similar problem on my lathe- the previous machinst (and I use the title reservedly) was in the habit of using a high pressure air hose to clear the swarf from the machine... needless to say, the aluminium swarf (chips) got everywhere and binded to the leadscrews- it actualy bent the axis leadscrew.

I'd be interested to see what results you got on a piece that was secured at both ends. I'd definately check previous posters' ideas about the tool height position.

Please let us know how you get on 'cos that is severe looking!

Good luck!

[HuFlungDung]

I bet if you wanted to produce knurled parts with that lathe, you couldn't make it cut like that no matter how hard you tried

I'd sure have to wonder about the tailcenter condition. Does this lathe use a tailstock with a dead center installed inside a 'live hub'? Might need to check for burrs and scoring, bad bearings, etc in the tailcenter and tailcenter taper.

[RickOmatic]

In regards to the "knurling".... Yeh, we did actually laugh at how hard it would be to make the chatter knurl on purpose!
In regards to the quad center....Yeh, that's the same one that we have, it gets hot (darn hot!) when it's used, and yes, we wondered if that might be the problem! So we will be gettin' a new one to try!
As for the chips. The machine is very clean, and we will check it out!

Thanks soooooooooo much for all the feedback! Regretfully, due to time constraints, I am finishing the parts on the Prototrak, but will be "experimenting" on some small diameters next week. If anybody has any other suggestions, PLEASE post them. The more I learn the better! Thanks! Rick

[HAILINHAAS]

show us your work holding and tools on the turret. The new haas lathes have added a counterweight on the tailstock head. ?????

[tobyaxis]

Well I haven't been doing this quite as long as everyone else but to be honest I would say that there is too much tool contact, too high of an RPM, and too little feed rate. Granted you most likely considered this factor.

If you can get this shop to buy them, try a VNMG430.5 which has a .007 nose radius. Max Depth of Cut should be around .03 to .07, RPM 1500 and Feed at .006 IPR for Roughing and leave .007 for finishing.

For Finishing a VNMG 430 with a nose radius of .004. RPM 1200, at .0025 IPR.

If this helps great, if it doesn't hopefully it will help someone.

BTW: Flood Coolant will help. Plus I noticed that no one asked what material this is, or I can't read LOL.

Cheers!!!!

[Sergeant]

RickOmatic, maybe a silly question, but are you using setting 107 for tailstock?

[TJJ]

Kinda late to post here.

Have you tried the SSV feature? If not check it out.

It's pulled my azz out of a pickle several times.

I use VNMG 331 for finishing where I can and sometime even leave a little extra stock for the final pass to load up the tool a little and dampen vibrations.