Fadal surface finish problem. Online diagnosis appreciated.

Oh Fadal, I love you and I hate you.

The latest fun thing to follow on with the chattering while climb milling in X+ direction but not in X- direction is terrible surface finish.

Here is a picture on the ends, nice finish, no problems.


And yet, here is a picture on the X axis travel. It actually has about .0003 waves on that surface.


The spindle is brand new and not the problem since it cuts perfectly on Y moves.

So my guesses are as follows.
1) X-axis bearings are either bad or no longer preloaded.
2) X-axis ball screw is misaligned terribly and causing binding.
3) X-axis ball screw is shite.
4) X-axis gibs are not adjusted right causing either slop or binding.

So which do you folks reckon it is? Any options I didn't think of to cause this?

Rig up an indicator on the spindle head to anyplace solid on the table in the X direction.
Zero the indicator, and shove on the table (only push in one direction, don't pull it back). See if the indicator returns to Zero after you remove pressure.
If not? X thrust is haggered. I am betting that is your issue.
Although, I had a buddy having similar finish issues in a HAAS once. And, it ended up being the opposite axis the finish issues were on.

Edit: Come to think of it, I was having minor finish issues in X on one of my HAAS's last year.
But only on vector moves (G1 X, and Y with or without a RAD). If it was a straight line X only move finish was fine.
Replaced the Y ball-screw because I couldn't stand listening to it any more! Finish issues went away.

If thrust bearings are good. Check for a bad resolver or encoder.

Any chance the interval of the .0003" waves is the same as the pitch of your Fadal's X-axis ballscrew?

Regards.

Mike

Maybe the y axis thrust bearing or ballscrew is going so it’s causing issues as you traverse the x.

I had a few minutes free today and put an indicator to it. It was about .0030 back lash from the thrust bearings.

I ordered another set and will redo that when I can squeeze it in.

Houndogforever said:

I had a few minutes free today and put an indicator to it. It was about .0030 back lash from the thrust bearings.

I ordered another set and will redo that when I can squeeze it in.

Click to expand...

Btw I just ordered thrust bearings for my fadal I bought them for $15 each from Misumi for nsk 7304bw bearings much cheaper than the fadal places.i bought 6 to do all my axis’s I got the seals skf 11138 from eBay for like $2.50 but zoro has them for $5 each and I got some shims at Misumi but I plan on reusing shims. For these prices it’s not too bad to just replace them all.

I know that is the listed seal, but that really confuses me. My ballscrew shoulder and end nut are both 1.060 dia journals where the seals should ride, however those 11138 seals have an ID of 1.125. So they are not sealing anything.

Houndogforever said:

I know that is the listed seal, but that really confuses me. My ballscrew shoulder and end nut are both 1.060 dia journals where the seals should ride, however those 11138 seals have an ID of 1.125. So they are not sealing anything.

Click to expand...

You may have metric ballscrews?

It is a DC machine from 1994 originally and I don't think they had metric screws then, plus my control is set as inch screws so I'm pretty sure that isn't it.

I am really confused now as to what the hell is happening. There is some mechanical issue but I am not smart enough to figure it out.

Let me show you some movies.
First off is the RH end of the table. This is a .0001 indicator on the front of the machined sub plate surface. As you can see, it is pretty smoooth.

Then moving to the center of travel, the same surface at the same jog speed.

And then we get to the LH end. And things go wacko.

So what the hell is causing the table to wiggle back and forth so bad at that end? Is this a gib issue, screw issue or what?

I'm so friggin lost now I just don't know what is happening. On a positive note, I did get the thrust bearings nicely shimmed and stable at about .0004 max back lash and for me, that is great.

Any and all help is appreciated or even a Fadal Guru in the Portland area that can do mechanical repairs. At this point, I would rather pay some guy $750 than F with it myself.

Thanks for any help.
Jon

Houndogforever said:

Oh Fadal, I love you and I hate you.

The latest fun thing to follow on with the chattering while climb milling in X+ direction but not in X- direction is terrible surface finish.

Here is a picture on the ends, nice finish, no problems.
View attachment 225979

And yet, here is a picture on the X axis travel. It actually has about .0003 waves on that surface.
View attachment 225980

The spindle is brand new and not the problem since it cuts perfectly on Y moves.

So my guesses are as follows.
1) X-axis bearings are either bad or no longer preloaded.
2) X-axis ball screw is misaligned terribly and causing binding.
3) X-axis ball screw is shite.
4) X-axis gibs are not adjusted right causing either slop or binding.

So which do you folks reckon it is? Any options I didn't think of to cause this?

Click to expand...

.
i have seen cnc with servo oscillation problem and its quite common for oscillation to be worse in one direction and much less going the other way. many cnc have a diagnostic servo screen to check oscillation. sometimes it can be tuned or adjusted electronically other times it is a mechanical problem
.
whens its real bad you can feel the whole cnc shaking. 50 ton cnc shaking bad literally can feel through your feet often from far away.

As i recall Fadal has 3 BackLash corrections Left, Center and Right. Maybe there is an large number in one of the settings?

obviously he has no experience with a big cnc servo oscillating so bad you can feel it shaking from far away

Well I have no clue on the seals they fit mine? But have you checked your gin straps and ways? Try putting a pry bar in the vise and moving it to each part of the travel then putting a little torque on it and seeing if you have deflection.

Also the maintenance manual has instructions on setting the master FeedRate and subsequently the servo balance and gain.

Let me clarify a little more. All 3 videos are moving in the same direction so it isn't a backlash issue. The BL for X is 3,3,3 so its not that issue.
I agree that it's like the gibs/straps on the LH end of the table may be too loose giving me some slop and wobble.
Once I get the brother set up and running, I will dig deeper and look into those gibs and give some wiggling to the table, see if I can't find this SOB problem.

Thanks for your ideas and suggestions.

Oh, and I did that whole clock setting thing recently and it came out right on. That was about 2 weeks ago when I was messing with the spindle.

Houndogforever said:

Let me clarify a little more. All 3 videos are moving in the same direction so it isn't a backlash issue. The BL for X is 3,3,3 so its not that issue.
I agree that it's like the gibs/straps on the LH end of the table may be too loose giving me some slop and wobble.
Once I get the brother set up and running, I will dig deeper and look into those gibs and give some wiggling to the table, see if I can't find this SOB problem.

Thanks for your ideas and suggestions.

Oh, and I did that whole clock setting thing recently and it came out right on. That was about 2 weeks ago when I was messing with the spindle.

Click to expand...

Ah well yea surely you will figure it out. So far fadal seem to be pretty common sense. All I can say for the seals is maybe you had coolpower ballscrews? The ones with coolant running through? If not you may have to ask one of the experienced fadal people.

Houndogforever said:

I know that is the listed seal, but that really confuses me. My ballscrew shoulder and end nut are both 1.060 dia journals where the seals should ride, however those 11138 seals have an ID of 1.125. So they are not sealing anything.

Click to expand...

My fadal 4020 is also a 1994. It has Metric ballscrews, 10mm pitch on X/Y and 8mm pitch on Z. Thurst bearings/seals are the same everywhere. 11138 is the correct seal, I think it seals on the outside of the bearing nut (it has a cylindrical section). There are two types of seals used. I think there are 3 larger ones used to seal the cooling passages, and the smaller ID one (11138) seals the other side of the thrust bearing.

I removed the cooling lines as everybody suggests, put some NPT plugs in to keep chips from falling in holes. I didnt like the idea of the remaining seals running dry on the ballscrew so i just installed the ones that are next to the thrust bearing (1 large and 1 small). Working fine now for about a year or so.

Also, the bearings I bought were supplied with a 0.001 shim. I dont think they actually measure anything, i think they just throw in a 0.001 shim and hope for the best. This shim didnt give me enough preload with my new bearings. I bought some 0.0015 and 0.001 shims from mcmaster so i could play around with preload. I forget now if i used 0.0015 or 0.002 but I did use more then what came with the kit.

Good luck with it, im not to sure if this is actually your problem or if its servo related, but it sounds like you could use new thrust bearings in any case. While you have it apart see if you have any preload left on ballscrew. I re balled my Y and Z and it worked great, nice improvement without spending a ton of time and money.