mori seiki nv5000 using peel mill

[mchin-pilot]

http://www.klubersolutions.com/pdfs/Tribol...t_Selection.pdf

[Mic]

I've seen this problem with damaged ballscrews on a couple of Hermle's. The reason was the same. Machining with very small oscillations in one axis. It's a general problem for all ballscrew machines. If you have a lot of toolpaths with these small oscillations it's a very good reason for looking at a machine with linear drives as they don't have this "limitation".

[Dave.L]

quote:

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I never greased my machine as recommended by the manufacturer

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That's for sure one way to NOT get warranty service.

 

When I rebuilt my live tooling head, BTW totally different than a ballscrew bearing, I think I used the grease you mentioned. I am home now and don't have my notes.

 

What I do remember is that the amount of grease is very critical. More is not better. I actually used a suringe to install the grease, 1 so I could measure the amount and 2 so I could get it into the ball track. I was blown away how little grease was required.

 

As a side note, rebuilding the head was not too difficult, however, it took a whole day to break in. And the break in is 100% related to working in the grease. If I remember corect, I stepped up the RPM in 500 PRM intervals while checking for heat.

[Newbeeee™]

Ok, throwing a curve ball...

Is this really down to small moves or a combination of small moves but with the servo tuning being out?

If the tuning is out, this could easily set up a resonant frequency which could do this? Vibration is a very powerfull thing.

Just a thought?

[Mic]

It has nothing to do with servo tuning. Small oscillations will over time press the grease away so it's metal against metal. This effects both bearings and the ballscrew it self.

[GoetzInd]

Well asuming the machine has 10mm pitch ball screws, .018 of motion is about 16.5 deg. at the motor. I can see this not being enough travel for the ball bearings to overlap on each other, thus working the grease out of the area.

 

Mike

[Mic]

a Matsuura MAM72-42V has 16 mm. pitch so here the ballscrew movement is even smaller.

[Chris Rizzo]

The microlifts feature could create this scenario along the z axis very easily.

[Mic]

quote:

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The microlifts feature could create this scenario along the z axis very easily.

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Very good point

[Bruce Caulley]

IMO any software or tooling company promoting this method should warn about this. Machine dealers also.

 

Bruce

[Dave.L]

quote:

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IMO any software or tooling company promoting this method should warn about this. Machine dealers also.

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Some may view this comment as "asking a lot", however, the software and the machine could have the brains to look out for this condition and warn or alarm. It would be mathematically possible, except the value of the stroke would be needed and it seems that that value is not being provided.

[Bruce Caulley]

It just needs to be a general warning in the help section and maybe at the bottom of the parameters page as well.

 

I remember the first time a tool rep showed me a feed-mill and warned about using them on machines with ceramic bearings. They were worried that people trialling these tools would start blowing up spindles. In the case of peel milling though the tooling companies have no control over what you actually do with a tool so it is a software/MTB responsibility to officially make these things known once they arrise.

 

I once saw in a user manual of an old VMC that these short repetitive moves should be avoided so maybe it is also mentioned somewhere in the huge volumes that seem to come with machines these days.

 

Do it quick CNC and score some much needed points in the customer relations dept.

 

Bruce

[patool]

just got back to work and read thru all of the replies to our peel mill situation.to help clarify a few things the machine is out of warranty. 3 years old with low hours.bearings are grease packed with no way to regrease other than remove and repack.we have had 2 service calls for new bearings.both times after running the same peel mill program.second time we were told it was the progam causing the damage.i posted this on the mastercam forum to see if this is a known problem with any machine and also as a warning so no one else does the damage to their machine that we did.we will be talking to fanuc in the near future about the bearing issue with the drive moter.the drive moter is still on the machine and has not been repaired yet.one other thing to add is that we had very little down time as boldt was quick to service the machine on both occasions.we still would like to know.how much stroke is enough?one thing for certain we will not be running peel mill with a small stroke again.thanks to everyone for the replies so far.

[Newbeeee™]

and to specify how much stroke would be required would be very difficult as a 'broad statement'.

You would need to know the pitch of the ballscrew and the diameter of the balls I would have thought?

Has no-one else had this problem, because there a few threads here encouraging the use of peel mill?

Also, trochoidal milling has been pretty well known for 10+ years, which is similar in principle.

 

patool: is your servo gain definately not a problem???

[patool]

servo gain is definately not a problem according to service.

[alanu23]

This topic is crazy! My Mori rep recommended peel mill! Ever since I have fallen in love. I have been able to take a 3/8" Carbide Hanita 5an3 1.6 L.O.C no radius down a .5" wide 1.5" deep 8" long channel on both sides of a part with a .080" web in the middle going 12k rpm at 150ipm... show me another tool path that can compete with that! Catia programmers... EAT YOUR HEART OUT...

[Chris Rizzo]

I think this could be a somewhat rare situation where his slot was only .007 wider than the tool. Very little range of motion. You've got .0625 on either side. It would be interesting showing this case to your Mori rep and see what he says, for your knowledge (and ours )....provided he's not just a salesman.

[Jim Walters]

Bob (From Boldt) emailed me i called him today he was saying .007 move would wear out bearing(greased bearing) in a week of running it that way he said.

if i had a .060 move it would not push grease out of the bearing at .007 move running all day for a week it would ruin bearing in a week he only ever seen this happan 2 times in 10 years and that was the cause of bearing going bad both times i belive what he was saying was right on i will use peel mill as long as im letting bearing move more than .060 in X or Y

Thanks

Jim

[Newbeeee™]

Not disputing this at all, but it would be nice to know why .06" is ok.

Is it a ratio of the metric balls/leadscrew pitch (60 thou being 1.5mm)?

And would 50thou be ok, or is that a no no?

Please can you ask him how he has arrived at this figure.

Again to stress, this isn't to dispute it's to understand.

I don't want expensive machine repairs, and I LOVE the peel mill cycle.

Thanks,

Terry

[Joe788]

Newbeee, I think the problem is that a .007 move isn't rolling the balls at all, it's just smashing them back and forth over and over and over and over, causing the false brinelling.

 

Totally unrelated to the OPs problems, but I just stumbled across this clip the other day with some ridiculous peel milling at the 43 second mark:

 

[Newbeeee™]

Joe,

I fully understand that 7 thou is virtually no movement. But the OP said that 60 thou is ok.

All I'm trying to get is how was this figure arrived at, and if 60 thou is ok, then is 50thou ok or no good?

ie there must be limits from a calculation somewhere. 60 thou can't just be a figure plucked from the sky, that's all I'm questioning.

[GoetzInd]

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All I'm trying to get is how was this figure arrived at, and if 60 thou is ok, then is 50thou ok or no good?

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It depends on the pitch of the ball screws and the number of balls in the bearing. If you know that, it is very simple to calculate.

 

Mike

 

[ 01-05-2010, 06:25 PM: Message edited by: GoetzInd ]

[Newbeeee™]

Mike,

Yes providing you know the 'formula' or ratio of what is acceptable.

But if you don't, the info is worthless???

[Odell]

One way I avoid repetitive movement on the same spot on the bearings when peel milling a narrow slot is instead of puting my parts in square with the machine table I put it in at an angle. As steep as I can get it.

[Steve Hattori]

+1 Odell !