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Haas VF2: Bad finish. Thrust bearings?

david n

david n

Diamond
Joined
Apr 13, 2007
Location
Pillager, MN
Milling some 6061 widgets...............this is the finish I'm getttin':ack2:(see pics)..................New cutter runnin 10K at 50IPM..............It's worse from about 5 o'clock to 1 o'clock...........second pic is around 3 o'clock....................what can I look fir? I did a trial cut with just straight cuts and it finished OKish............... interpolating is where the issues crop up.................



IMG_0786.jpg

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Looks like chatter, what size, shape, length endmill are you using?

Are you ramping down?

Have you tried leaving 10 or 15 on it and doing a full depth finish pass at reduced rpm and feed?
 
Thrust bearings usually growl at 100% rapid and may show a few tenths lost motion with an indicator.

Is it noisy during rapid moves? One axis louder than the other?
 
What year is the VF2 and what software is it running? Do you have HSM option? What cam are you using? What dia EM was that?


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On the hardware side I have seen on well used machines that the ballscrews need to be modified or recalibrated and tightened up. Usually and ballbar test will reveal hardware issues such as ballscrews being out of whack. Certainly not a cheap test but it could be the problem.

I have seen machines so loose down there that they literally suck the entire table into a cut and cut way beyond the programmed path. Or watching the entire table stutter as the cutter is pulling all that mass into the cut. Cutting a circle with that loose of a machine is an exercise in futility until the root is solved.
 
Thrust bearings fixed a lot of that "faceted" look on my milltronics. They were noisy at rapid speeds and you could almost feel the machine pulsing when cutting at 40-50 ipm. Didn't realize how bad they were until I put new ones in and heard how quiet the machine is now.

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Check the play in the spindle both radial and axial. Also check backlash even if it’s comped out it may still cause issues. But it’s a haas so I wouldn’t expect miracles
 
I'm thinking your feed is too slow on the finish pass. The vertical lines I see there usually show up when that's the case. You'll have to juggle amount of material for the finish pass, end mill conditions, and feed rate. End mill conditions - diameter, length, holder type, helix, how sharp is it (sometimes a little worn is better) and other stuff. Sometimes a company has a better grind. Variable flute will likely give you a better finish. I used to love collets for everything, but I've found that sidelocks can work better many times. Good luck.
(and all the other stuff above lol)
 
The floor finish away from the wall also looks kind of rough. The wall facets kind of what I've seen if you try to finish with adaptive roughing settings/loose tolerances... IDK.
 
When I thought my thrust bearings were shot I took a 2” facemill and did 100 thou full width cut in steel in the x then in the y. Yup x thrust bearings were shot. Not sure if that is the issue here or not. I’ve seen programs do this before, but if they are G02 and not a ton of short segments imitating a circle then that would rule that out. My Vf2 doesn’t have hsm and finishes just fine. It is a 2015, not sure what year this one is.
 
It’s not a cutter or programming issue……. these are repeat parts….. same set up/same program/same tooling. It’s either mechanical or could be a servo…………..
 
david n said:
It’s not a cutter or programming issue……. these are repeat parts….. same set up/same program/same tooling. It’s either mechanical or could be a servo…………..
Click to expand...


But it could be drawbar as posted above.
But you wouldn't think that would be in one quadrant, but ???
... but that could 'splain the marks on the floor?

Any chance that you have a pull tester?


----------------

Think Snow Eh!
Ox
 
Ox said:
But it could be drawbar as posted above.
But you wouldn't think that would be in one quadrant, but ???
... but that could 'splain the marks on the floor?

Any chance that you have a pull tester?


----------------

Think Snow Eh!
Ox
Click to expand...

That is another thing to check..................
Floor marks are from the notched rougher EM..............she's haulin' to plow off the most of the material...............floor finish is always like that........I have left anywheres from .01-.05 for the finisher and same results each time.................................

I pulled way covers and everything is gittn' oil and looks OK......................check spindle run out.............it's around .0001ish..............

Then I gave er the old push pull exercise on the table............................

 
Last edited:
Milland said:
Unless you're the Hulk, that seems like a lot of movement.
Click to expand...

It's definitely too much..............thrust bearing must be gittin tired...........

Funny though...............on new Haas machines, you can get the table to move an indicator needle..............I tried it on my Doosan and Brother..................needle would not budge.
 
david n said:
That is another thing to check..................
Floor marks are from the notched rougher EM..............she's haulin' to plow off the most of the material...............floor finish is always like that........I have left anywheres from .01-.05 for the finisher and same results each time.................................

I pulled way covers and everything is gittn' oil and looks OK......................check spindle run out.............it's around .0001ish..............

Then I gave er the old push pull exercise on the table............................

Click to expand...

The fact that it returns makes me think it may not be the thrust bearings. Although they may also be going bad and getting louder

Checked the thrust bearing mountings on both ends of the screw. Not a haas but on another machine I was having issues and turns out 2 of the 4 bolts that hold the housing to the casting were broken and under decent cutting loads or rapids it would flex. But was difficult to detect because backlash looked fine.

Also on less rigid linear machines I’ve seen similar but not as bad numbers. Just the nature of cheap linear rails on not so heavy castings with improper mounting.
 
I'm following this thread with great interest, since I have the same problem on an Arrow 2000 with scales. New thrust bearings on X and Y and still no difference. Leads me to suspect the ballscrew in my case but it's kind of hard to do the backlash test because of the scales..
 
I would also guess thrust bearings as my first assumption. Here is another thing to check for though... is the machine level. We had a CNC that was rocking on two feet because it wasn't level. When running it fast the finish was crappy on just one of the quadrants of the part. Easy fix, wish we checked that before we had a service guy come in to tell us.
 
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