Fadal Belleville Washers

I know there's tons of threads on this subject and I've searched and read as many as I could find, but haven't really found an answer to this. Interested in thoughts on what could be going on here.

Between my business partner and I, we have three Fadals: a very old (but very tight) VMC40, a 1999 4020, and a 2000 4020.

Last fall I pried open my wallet and got a tool holder test gauge (CAT40)

The VMC40 got an all-new spindle with drawbar a few years ago. It measures north of 1600lbs of pressure.

The 1999 4020 was showing about 400lbs. We replaced the bellevilles (I don't know the count) and it came up to about 1500lbs.

The 2000 4020 was showing about 600lbs. I replaced the bellevilles and it only came up to about 850lbs. This has me scratching my head a bit.

Here's the details. This is the first time that machine has ever got the bellevilles replaced. The spring pocket is the 4.627" depth, which calls for 44 washers. I removed 41 intact washers and enough fragments to account for the other three. Not that it should matter (I don't think) but this is a 28" Z machine, the only one of the bunch.

I replaced the floater, even though there really wasn't anything wrong with the old one. I couldn't see anything really wrong with the drawbar either, other than some wear on the portion of the shaft that sticks up through the springs, apparently from the springs rubbing on it. The tool retention end of it looked fine and none of the ball bearings fell through the holes or anything like that. I used anti-seize to hold all the balls in place for the installation of both the floater and drawbar.

After installing 44 brand spanky new washers, all gooped up with anti-seize, I got the rather disappointing 850lbs result. It actually started out about 900, but it seems like they lose 50lbs rather quickly as the springs settle in.

I then added two washers, bringing it up to 46. It wasn't particularly difficult to compress them to get the keepers on. I got about 1050lbs after settling.

The washers come in sets of 47, and I didn't really want to put an odd number in there because you need an even number to orient them the way the drawing shows (cup down on the bottom washer, cup up on the top washer). So I ordered in another full set.

I went ahead and pulled out the 46 brand new washers and tossed in 46 brand newer washers. Same result, there wasn't a dime's worth of difference.

Them I added two more. I'm up to 48 now, which is getting close to the limit of what could go in there and still get the keepers on. The stack sticks well out the top of the spring pocket prior to compressing them all. I dunno, maybe I could get one more in there, but I highly doubt I could add two. I got 1250lbs, settling to 1200.

Which I suppose is OK. I mean, it's working, and it's twice as much as I had before I started this little exercise. But I can't figure out why this machine shows so much less pressure than the other machines. It's a mystery to me.

More details: Same tester was used on all three machines. Also I loaned the tester to another local shop and after changing the washers on his 4020 he reported north of 1500lbs. Also, I measured the dimensions of the original springs and the new replacements and they appear identical in all respects. Same thickness, same diameter, same height.

Any ideas? Is there something wrong with the drawbar itself?

We have a 4525 and a 3016. I borrowed a drawbar tension gage from another shop. The 4525 was less than 900lbs and the 3016 at 1500lbs.
We had a service tech come in to replace the bellviles. He put his tension gage in and both machines measured about 1500 lbs. We double checked with the borrowed gage and the readings were the same as the initial test.

I spoke with the gage manufacturer. Occasionally the the small end of the gage taper will hit the drawbar assembly and give a false reading.

The solution is to neck down the short end taper about 1/4" long.
We did not do it, because it wasn't our gage

I am sure you checked, but what is the air pressure on each of those machines, 120 psi max?, If I am not mistaken anything above 1000 psi on the force tester is ok seem to me around 1100 - 1200 is what mine came in at on a new set of bellevilles. Is the knock out cap (I think thats what its called) at the top of the draw bar worn. It's been awhile since I have worked on a Fadal, so my memory could be just a bit foggy.

jcoehlo said:

We have a 4525 and a 3016. I borrowed a drawbar tension gage from another shop. The 4525 was less than 900lbs and the 3016 at 1500lbs.
We had a service tech come in to replace the bellviles. He put his tension gage in and both machines measured about 1500 lbs. We double checked with the borrowed gage and the readings were the same as the initial test.

I spoke with the gage manufacturer. Occasionally the the small end of the gage taper will hit the drawbar assembly and give a false reading.

The solution is to neck down the short end taper about 1/4" long.
We did not do it, because it wasn't our gage

Click to expand...

That's interesting, thanks. I don't have a second gauge to compare it to, but that's good to know.

tmt said:

I am sure you checked, but what is the air pressure on each of those machines, 120 psi max?, If I am not mistaken anything above 1000 psi on the force tester is ok seem to me around 1100 - 1200 is what mine came in at on a new set of bellevilles. Is the knock out cap (I think thats what its called) at the top of the draw bar worn. It's been awhile since I have worked on a Fadal, so my memory could be just a bit foggy.

Click to expand...

Does the air pressure affect the tool holding force? It seems like it's just the bellevilles. Or am I missing something? Because this machine does have a little lower air pressure than the others, I've got it turned down a tad. But I don't see how air pressure affects it.

Y'know, in my reading, I've seen that some machines come in low like mine after new bellevilles, and some come in high. I'd really like to understand why.

I inspected the spider and sure didn't see anything wrong with it. I put a little anti-seize on it's ball bearings just to make sure they didn't fall out as I was handling it. The little cap that goes on top of it seemed fine too.

I had all kinds of bad expectations about the condition of things, after reading threads and horror stories about grinding out the floater with a dremel, and seeing pictures of shot drawbars. I was really kind of surprised at how good everything looked. Really the only thing "wrong" I could find was the three broken washers, which I guess is not uncommon. The machine has had a handful of crashes over it's nearly 20 year life. It's not a machine that's in constant use, though, it probably runs an average of 20 hours per week or something like that. I suppose I could look up how to check it's spindle hours. The drawbars are getting a little loose, it's got some backlash, but other than that it runs good.

ZfMax said:

That's interesting, thanks. I don't have a second gauge to compare it to, but that's good to know.



Does the air pressure affect the tool holding force? It seems like it's just the bellevilles. Or am I missing something? Because this machine does have a little lower air pressure than the others, I've got it turned down a tad. But I don't see how air pressure affects it.

Y'know, in my reading, I've seen that some machines come in low like mine after new bellevilles, and some come in high. I'd really like to understand why.

I inspected the spider and sure didn't see anything wrong with it. I put a little anti-seize on it's ball bearings just to make sure they didn't fall out as I was handling it. The little cap that goes on top of it seemed fine too.

I had all kinds of bad expectations about the condition of things, after reading threads and horror stories about grinding out the floater with a dremel, and seeing pictures of shot drawbars. I was really kind of surprised at how good everything looked. Really the only thing "wrong" I could find was the three broken washers, which I guess is not uncommon. The machine has had a handful of crashes over it's nearly 20 year life. It's not a machine that's in constant use, though, it probably runs an average of 20 hours per week or something like that. I suppose I could look up how to check it's spindle hours. The drawbars are getting a little loose, it's got some backlash, but other than that it runs good.

Click to expand...

Air pressure has nothing to do with it. as the airs only purpose is to RELEASE the tool from the drawbar.
There was another thread not to long ago about someone putting the draw bar back together using the wrong snap ring groove.
your drawbar could be stretched but I doubt it. if your drawbar was smooth and not dinged to shit you should have been fine.
lots of machines have different numbers of washer counts so make sure you look at the charts for your specific machines. Fadal CNC has that chart along with the proper measurements.

I would stuff as many bellvilles in the spindle that I could, and drive 'on. (As Ox says...)

Do make sure the drawbar air-cylinder rod is retracting completely clear of the spindle...

The cylinder is a rectangle, and the aluminum piston inside can bend or crack. New ones are cheap...like about anything for a Fadal.

I owned a VMC 3016 (box-way, rigid little bastard) for about 10 years, but sold it a while back. We needed the floorspace, and I wanted to be 100% Yamazaki (again, as Ox would say). Older Yamazaki mind you, but I've learned them inside, out, and backwards, ....and have hoards of spare parts.

ToolCat

Thanks for the comments guys, I appreciate it. It gives me some more things to think about.

I don't think that air cylinder rod is the issue, just because when assembling, it sits flat over the belt guide. If it was preloading the drawbar I would think it would hold the assembly up a little. But it's a good thought, it's something that never occurred to me.

I may just replace the drawbar and the little ball bearings that go in the tool holder end of it. A drawbar isn't cheap, but it's not like it's ridiculously expensive or anything. That way I'll know everything is new. And I've gotten good at pulling the thing apart and putting it back together, it doesn't take me long, so that part doesn't bother me. If that doesn't bring the pressure up, maybe I'll try to squeeze a 49th washer in there.

Thanks again guys.