mori seiki nv5000 using peel mill

[patool]

we were running a mori seiki nv5000 using a .187 dia endmill cutting a .205 wide slot 33.5 inches long using peel mill.cycle time was 35 minutes. total pcs ran was 22.machine went to xyz home after each part.shortly after this job we noticed a noise from our y axis.our mori dealer checked the machine and informed us the bearings on the y axis ball screw were shot along with the bearings in the drive moter.they are blaming the peel mill program.they said there was not enough stroke to lubricate the bearings.they will not tell us the minimum stroke that is required to lube the bearings.has anyone else had this promblem or know the minimum distance?tool life was unbelievable using the peel mill and it was really the first time we tried the program.may be the last until we get a distance.by the way the machine has 2500 hrs on it

[Dave.L]

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dealer checked the machine and informed us the bearings on the y axis ball screw were shot along with the bearings in the drive moter.they are blaming the peel mill program.they said there was not enough stroke to lubricate the bearings.

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The way a Mori is built, I think this is

 

How old is your machine? Is Boldt your dealer down there?

 

Sounds like lots of pieces to the puzzle are missing from this. I have never, ever heard of resrticting your machines motion to avoid mechanical damage like this.

[patool]

boldt is the dealer and the machine is 3 years old

[Dave.L]

Boldt is our dealer as well. Be sure to discuss this with Bob Meade (manager of service). Bob's a sharpe, level headed guy and I cannot image he is the one telling you that the peel mill cycle killed the machine.

 

I hope it works out for you coz that machine probably cost 180K

[patool]

bob is the one telling us this

[Dave.L]

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bob is the one telling us this

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Wow, I cannot believe it. If that's the case you may need to find a way to get Mori directly involved.

 

I hope it all works out for you.

[Jim Walters]

Wow i was looking at doing this on ares we have 2 NV5000 mori seiki best cnc i ever ran so far better than the fadals super max johnfords i ran before can't beleave that it would do that but i better check this out before i run it that way

Jim

[SydwazShawn]

No way!! Was this machine ever crashed? Its no different than machining a small part with very small work envolope. Something else has to be wrong. If not than Mori needs to state it in there warranty documents! I use peel mill on my Haas and have done it for alot longer than that with no problems! If Mori cant outlast a Haas, they need to drop the price! Maybe one or more of the oiler injectors got plugged up?

[Greg Williams]

Do the slides and the bearings use Grease or oil for Lube?

[Dave.L]

Greetings Forum Members,

 

This situation is very concerning to me for several reasons. First, I have yet to use the peel mill cycle and to be honest, I don’t quite understand the benefits of this cycle so any input would be appreciated.

 

Since the machine in question was sold by a dealer I too have bought equipment from, I was curious as to the technical explanation of what happened. We don’t have a NV5000, however, the issue really did not seem to be a machine related problem.

 

With that said, I sent an email to the service manager who I know very well.

 

I received replies from him and the president of the dealership and I wish to share the technical points in hopes that we can all learn something here and PREVENT a repair like this on our equipment or the equipment of the forum members.

 

Here is what was stated to me:

 

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Bob Meade:

 

Here is what I found. The customer was cutting a slot of some length in the X axis direction. Instead of using straight X and Y axis moves, they used the “Peel Mill” cycle. We have no issue with the Peel Mill cycle in and of itself; the issue with the customer using the cycle in this case was the fact that the cutter was so close to the final size of the slot that the Y axis moved Y+ then Y- over a distance of only .007” for over 45 min. This short distance back and forth means that the bearing rides over and over in the same sport and forces the grease out of that spot. In other words the bearing will run dry in that location causing extremely premature failure.

 

I had seen this failure before in Z axis with 3D milling. The customers Y axis servo motor is also noisy and I explained that the motor bearing failed for the same reason.

 

The bearing can not lubricate itself properly in application the customers program dictated

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Mike Ahrens:

 

I suspect that it is hard to believe that a condition like this can occur, and bearings can wear out so quickly when there is hardly any load being applied. But this condition is in fact widely known, and is referred to as "false brinelling". If you are interested, here is a link to the Wikipedia article

http://en.wikipedia.org/wiki/False_brinelling

and here is another short description

http://www.engineersedge.com/lubrication/f..._brinelling.htm

. If you google "false brinelling" you'll get many other articles, but they all say basically the same thing.

 

As Bob has said, the issue is not with the peel mill cycle itself. Any small oscillations can cause it. The customer in Meadville was making small movements back and forth, as described in the linked articles. It is my opinion that this situation could occur on any machine using steel roller grease packed bearings to support the ball screws. The fact that the Fanuc motor bearings are also worn backs up my observation that this is not a problem that is unique to Mori Seiki.

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[SydwazShawn]

WoW! I guess in all fairness my peelmoves were not that small, but damn that sucks. Logically it does make sense. Still though it was only 35 minutes of machining, and then he hommed it between parts! You would think it would relubricate the bearings?

[Chris Rizzo]

Sounds technically plausible, regardless it's not the customers fault unless it is explicitly stated in documentation (which I can't imagine it is?). What's the range of motion needed to prevent? Article says the roller spacing? Hey maybe Haas' are better...no bearings!

 

[Dave.L]

Chris, I'm not sure I understand your reply. I should have also added that the machine is out of warranty, which is probably the legal document here. I was trying to share the technical info without getting between the two parties, I have no interest in that.

 

Trust me, I too have issues with time based warranties since I have had live tool heads burn up way too premature.

 

My whole point is posting this is to help others avoid this situation, I'm sure it was not cheap

[Chris Rizzo]

Good point Dave. I think most of us have had seemingly premature machine failures, and it's frustrating and infuriating. I've fought the good fight a few times and gotten two machines wholesale replaced (yes in warranty), and a fair amount of out-of-warrantly-gratis service.

 

In this instance, I just think of all the machines in use worldwide, esp mold making, and this would be a more common or known occurrence. If so it would be part of a machine use criteria, just like a duty-cycle on a motor.

 

I'm certainly not a lawyer, but there is some reasonably implied-usage issues here.

[Dave.L]

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I think most of us have had seemingly premature machine failures, and it's frustrating and infuriating.

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I can't image for a second ever being the lead of a service department, talk about a thankless job.

 

You know, the machines always go down when you need them most, out of warranty and when you have the least amount of money in the checking account

 

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and a fair amount of out-of-warrantly-gratis service.

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In my experiences, the dealer as mentioned here (Boldt) has done this for me too. In the example of the live head failures, they sent me about $1,000.00 worth of parts and I rebuilt the head myself.

 

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In this instance, I just think of all the machines in use worldwide, esp mold making, and this would be a more common or known occurrence

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Chris, great point, I agree. And the biggest reason I got involved in this, I want to help get this out so it does not happen to someone else. Am I nervous to try this cycle now? you bet. Will I try it with knowledge to make substantial axis moves? you bet.

[MotorCityMinion]

"I don’t quite understand the benefits of this cycle so any input would be appreciated."

 

Somebody step in and correct me if I'm wrong here.

 

My take on this: The tool never engages 180.DEG worth of material in the cut, and would always be climb cutting, thus lowering loads and allowing higher feed rates, at the same time offering elevated SFM's relative to traditional tooling. Traditional slotting with an emill axially is neither climb or conventional cutting, and rags on the tool. Although with a peelmill path, you do end up taking substantially lighter cuts in Z, your over all material removal rates should increase and your tool life will increase exponentially, allowing you to remove more material between tool changes, actually being able to complete a cut that would traditionally force a stop and fresh tool change or insert index at some random location. That sound like alot of BS? Well, I tried., lol. Anyway, searching the forum will lead you to some interesting tooling such as the Mitsubishi AJX. If ever there was a style of tooling that should be mandatory in a Machining center, this would be it. No sh@t, I get a huge kick out of watching the looks on peoples faces who see this type of tooling run for the first time. These tools offer up greater length of cut to dia. ratios and go where traditional tooling can't. They also work good with core rghing, surf rgh pocket and traditional 2d contour style toolpaths. Manufacturers will state a theoretical corner radius for the tool and you program it as if it were a bull mill. Get a tool rep to let you demo one, you won't regret it. And yes, it runs great on a Haas as well.

[gcode]

Last summer I had to mill about 40" of .250W x

.220 deep slot in a 304 SS weldment.

My first attempt was with a high end 7/32 stub length carbide endmill. It failed instantly.

I tried a peel mill toolpath with a generic

uncoated 3/16 double end stub carbide 4 flute.

The machine tool was a huge HBM with a 2000 max rpm spindle. Hardly the ideal candidate for peel milling.

Feeds and speed were 2K rpm .018 stepover and

15ipm.The cycle was nothing to brag about, but one endmill roughed the whole 40" of slot and it took a microscope to figure out which end we used

 

[ 01-01-2010, 07:53 PM: Message edited by: gcode ]

[baba]

Peel mill cycle/ I never heard of it until now. Yes I am old school but it's so great to learn new things. Thanks for posting this "situation". Learning is always deeply rooted in unfortunate events. I never heard of Bearing failurte for not making enough table travel over a long period of time. That is mfg. design of machine flaw. What a terrible way to have your CNC mill fail by simply "USING IT NOT ENOUGH". I will make it a good practice to take some time to Jog the machine to stroke it's axis when doing "STATIONARY" work. I won't feel like it's wasting time by flushing chips and jogging the stroke of the ways, I usually do this because I like to keep it set-up ready and Quick clean condition, but I felt guilty about uneccessarily stopping the cycle times. Now I am prolonging bearing life as well as reducing the mess. I really wish you a great turn around in your situation, you will see that this DOWN TIME is relevant to your EXPERIENCE UPGRADE.

[Guest CNC Apps Guy 1]

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...They said there was not enough stroke to lubricate the bearings. They will not tell us the minimum stroke that is required to lube the bearings...

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[Greg Williams]

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...They said there was not enough stroke to lubricate the bearings. They will not tell us the minimum stroke that is required to lube the bearings..

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[Guest CNC Apps Guy 1]

Is Mori turning into Apple? Rejecting warranty claims just because they feel like it? Those hours are just a hair over 1 year's worth of hours @40 a week.

 

WOW... just WOW???

[Dave.L]

Its a time based warranty, just like ever other. I dont love it, it is what it is.

 

Also, this happen multiple time to this machine due to the same cycle

[Greg Williams]

This policy may well be a problem for DMG-Mori

[mchin-pilot]

I used Kluber ( Made in Germany) A Very expensive! grease for our Japanese HSM Center.

 

It is made to overcome such situations.

 

I never greased my machine as recommended by the manufacturer( which recomends couple of weeks or so many thousand hours).

Rather I pumped little every few days depending how I used my machine. My work envelope was proportionally small and long cycle time. On some situations I have even pumped grease during machining of my part.

 

Today reading your problem I exactly realised that I could foresee and I can say why I did this to my machine.

[Bruce Caulley]

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I don’t quite understand the benefits of this cycle so any input would be appreciated.

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In parts where the slot is close to the tool as described, I have usually had better cycle times not peel milling and using a good carbide RMR designed for the material or a variable pitch end mill. Only time peel milling in a narrow slot was an advantage for me was in 6al4v Ti and the slot depth was 4 x width. 14mm slot 50mm deep.

 

I know there are some specific machine/tool/material applications where peel milling for extended times may be ab advantage, but IMO too many people don't understand the pros and cons and use it because it is "new and cool".

 

Bruce