MV-40B draw bar clamping force

I'm seeing signs on my tool holders and my work pieces that lead me to believe the pull force from my draw bar is not up to bar. During light cuts i can see marks indicating the tool holder is moving in the spindle. It doesn't happen during heavy cuts.

I don't have a spindle draw bar force gauge. I looked around and I see they can be had for about 1k.... I'd prefer not to shell out if I will only use this thing once every few years.

Would it just be wise to go ahead and replace the stack of belville washers on the drawbar? Is this something where you need a gauge to verify or if you just replace the washers it will be correct?

How difficult is it to access these parts?

Anything I need to be aware of safety wise while trying to get to them?


Machine is 1988 MV-40B with a 8k RPM spindle and Fanuc 10m

1800 LBS is minimum. Carefully pry between the spindle nose and tool holder flange. If you see any movement its bad. 1988 MV is right in those between years, so need to know if this is the old style gearbox machine or double wound integral spindle, and, thats right in the years where they used a ball bearing draw bar lock as well. Either way, the integral type spindle is not a slam dunk getting the drawbar out and back in if you've never done one. As far as the springs, you will need the correct parts list, since if they are broken it may be difficult to see how they are stacked and how many. The springs can be bought from Why choose us? once you know the size. There is most likely some O-rings you will need, and possibly the retention knob collet ($$$) as well.

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Originally Posted by underthetire

1800 LBS is minimum. Carefully pry between the spindle nose and tool holder flange. If you see any movement its bad. 1988 MV is right in those between years, so need to know if this is the old style gearbox machine or double wound integral spindle, and, thats right in the years where they used a ball bearing draw bar lock as well. Either way, the integral type spindle is not a slam dunk getting the drawbar out and back in if you've never done one. As far as the springs, you will need the correct parts list, since if they are broken it may be difficult to see how they are stacked and how many. The springs can be bought from Why choose us? once you know the size. There is most likely some O-rings you will need, and possibly the retention knob collet ($$$) as well.

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Whats the best way to to verify the spindle type?

Any clue how many hours/$ it would take a tech to do something like this?

If the spindle stops to change gears, its a gearbox. If you command 8K and hear just a click from the electrical cabinet ~2K rpm its an integral. Also, the gearbox machines usually have a sight glass in the head for oil.

A good Mori tech can do the job in 4 hours usually. If the drawbar shaft needs polishing, it could take a little longer.

It has the 2 speed gear box. Sounds like that might be easier for the rookie drawbar spring changer?

Yes, at least you don't have to deal with the built in sensor and sensor ring (i think). This is probably a machine that has a hydraulic unit in the back then? You will need to start with a tool in the spindle, pull the unclamp cyl/piston assembly off, remove the upper spindle nut and drawbar lock if it has one. Be careful, Mori puts 3mm set screws around the nut to keep it from backing off. Remove the screws completely and check to make sure they are not a double set screw. Its tight in there. Once you spin the upper nut off (they can be a real B*tch) bolt the unclamp cyl back on. I usually use all thread when re assembly here. Unclamp the tool from the spindle, and let the unclamp cyl re-clamp. Now, lots of spring pressure still on the cyl. Slowly back off the nuts on the all thread until the spring pressure is relaxed. ( i also made a manual press plate at one time for doing this). The draw bar will hopefully pull out now. If it's really stuck, a peice of 5/16 rod helps here. Put the rod up to the drawbar, lower Z axis and use the machine to push the drawbar out. Cautions: dealing with a lot of spring pressure, especially when putting back together. Try not to unhook oil lines on the unclamp cyl if the machine is not a hydraulic type, bleeding the system can be a PIA sometimes. Heavy black lithium grease on all springs and drawbar.
Tips, use a very short tool holder while removing the upper spindle nut. You can use the flange to clamp on the table vise if needed to keep the spindle from turning. Make sure you have hydraulic fluid on hand. If its a non hydraulic machine, remove compressed air while re-filling the unclamp Cyl less take a hydraulic oil vapor shower.

It has the oil cooler mounted by the rear left of the machine if you thats what you mean.

I know I hear compressed air blow off sounds during tool changes.

No, it would have a noisy hydraulic unit. You have the air/oil closed loop drawbar unclamp cyl. then. I recommend not removing the threaded hose on this unit, just set it aside. Bleeding those can be a PIA sometimes. I can pull entire spindles without having to bleed those, so i know it can be done.

Sounds right... about the air / oil closed loop.

You wouldn't happen to have a service manual for performing this task would you?

I never saw one the entire time I worked for the distributors/Mori. Think the first one I did took me 10 hours, those places are trial by fire. Do the job or go home. I can probably have one out in 30 minutes now, well, when I was in better shape. Probably an hour now, soft job is making me slow.

ok. It would be nice to figure out a parts list before I dive into this thing... especially if there are any o-rings I should be replacing in there.

Most do have o rings, and I can tell you Mori was about a grand for the springs, last time I bought from key I think they were about a 1.50 each, so around 100 bucks. You might get someone from Mori to email you the parts list. I don't have access any longer.

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Originally Posted by underthetire

Most do have o rings, and I can tell you Mori was about a grand for the springs, last time I bought from key I think they were about a 1.50 each, so around 100 bucks. You might get someone from Mori to email you the parts list. I don't have access any longer.

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woah, they charge 100 dollars each for those washers? :eek:

They were super high. Don't remember price per each, but key was 1/10 th the price. Downside is you need to measure what you have then order the correct springs, some shops wasn't worth the downtime, some were. I used to stock for the common machines and still made big profits and charged half of Mori price. (When I went out on my own).

Quote:

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Originally Posted by underthetire

1800 LBS is minimum. Carefully pry between the spindle nose and tool holder flange. If you see any movement its bad.

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I tried to use a prybar and didn't see much movement, I did notice that i can spin the tool holder slightly in the spindle with my wrist until it hits the drive lugs.... would that be indicative that the clamping force is low?

Yes, that indicates a sort of major problem. Tool should be super tight to where you can barely move it with a wrench, if you could get on it good...

If the Bellevilles aren't bad, it could be binding due to rust, corrosion or no grease in the stack and on the sides of shaft. Could also be faint steps in moving parts hanging up motion.

If you have a question about the springs, call SPS in NH, not only do they stock, but have the experience to know what OEM parts were used in most cases.

Just measured the clamping force and read 1300 lbs. Seems like i should probably take it apart and refresh the stack!

Quote:

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Originally Posted by underthetire

1800 LBS is minimum. Carefully pry between the spindle nose and tool holder flange. If you see any movement its bad. 1988 MV is right in those between years, so need to know if this is the old style gearbox machine or double wound integral spindle, and, thats right in the years where they used a ball bearing draw bar lock as well. Either way, the integral type spindle is not a slam dunk getting the drawbar out and back in if you've never done one. As far as the springs, you will need the correct parts list, since if they are broken it may be difficult to see how they are stacked and how many. The springs can be bought from Why choose us? once you know the size. There is most likely some O-rings you will need, and possibly the retention knob collet ($$$) as well.

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Working on the process now, I think i may have take apart a little more than necessary but im not sure.

Started w/ a tool in the spindle.
Removed the upper unclamping cylinder via the 4 long bolts and jam nuts.
removed the spring thats bolted to the top large plate that the unclamping cylinder bolts to
removed the thick plate that the assembly bolted to
Undid the set screws,
Removed the upper spindle nut.

Now I believe i have to reassembly the unclamping cylinder so i can get the tool holder out of the mill and at that point the pressure on the bellevilles will be released.

I'm not sure if they pull out of the top or the bottom at this point.

I talked to Mori and the machine spec is 1320 lbF to 1760 lbF.

So it was on the bottom end of the spectrum.

I got it all disassembled and did not see any broken washers, fortunately.

The draw bar comes out the top on this machine.