[nburgey]

My company just bought a used Okuma MB8000-H. The machine came in pretty bad shape but overall runs well. After about a week of running, the High Pressure Coolant Fitting that attaches to the back of the hydraulic cylinder on the back of the spindle/drawbar broke. I actually had a 1/2" JIS nipple and replaced it rather easily. After 3 shifts it broke again, so I replaced and made sure all my lines and moving components were not hitting or rubbing on anything including making sure I am not hitting the cast frame on the "Y" axis when it goes as far down Negative the machine will allow. 3 shifts later the fitting again broke. I now took the cylinder apart cleaned made sure everything in it was working properly and put a new fitting in. I also checked the thru coolant pin and spring inside the nose of the spindle and checked the drawbar clamp force. After everything checked out I let the machine run. Again the fitting broke. I am now out of ideas. What could be causing this??? I am not sure where to look next... I did turn the high pressure coolant down from 1,000PSI to 400PSI and made sure all tools that used it were not plugged. Please give me your thoughts, any suggestion is worth trying at this point.

[Jim Dawson]

Sounds like vibration is causing this. Is something bent or out of alignment? Is it possible to use a flexible fitting in that area?

[nburgey]

we do have a lot of vibration on the part that is running. I am not sure what kind of flexible fitting I could use. There is also a "T" that has an air blow and check valve for the air blow attached to it, that would be hard to support. Any ideas?

[Jim Dawson]

Can you post a picture of the area? I've never seen an Okuma lathe. Maybe a short piece of hydraulic hose attached to the connection point? Might take a little bit of re-plumbing.

[nburgey]

it is actually a 800MM Horizontal Machine Center. I attached a parts drawing of the thru spindle piping. Item 25(32) is the fitting that is breaking.

[Jim Dawson]

The drawing is perfect ! It looks like there is a lot of mass hanging off of that fitting. As said above, I would add a piece of hydraulic hose in place of the fitting, then support the Tee assembly off of what appears to be a support bracket, item 2(42), maybe with a couple of heavy zip-ties.

Based on the 1000 Nm spec, I would expect the nipple to have about a 1/4 inch hole through it. If it has a larger hole It may be too weak to stand up to the vibration. Maybe a high pressure stainless nipple would be a better choice.

[nburgey]

thanks. I actually have a SS high pressure nipple ordered and supposed to arrive any minute. it is rated at 2400 psi so if that doesn't fix it I will try a piece of hydraulic hose and will also make a bracket to help support.

[Jim Dawson]

If you do have to install a hydraulic hose, come out of the spindle with an elbow and put an elbow in the Tee. That will allow a loop in the hose and allow easy installation, as well as adding more isolation from the rest of the hardware.

[deadlykitten]

hello nburgey what jim dawson said, regarding that the nipple has to sustain a lot of mass, sounds pretty realistic

the "lathe" spindle rapid movements, and all that pipe mass & inertia involved may be enough to break the little nipple

i suggest look also at the pipes, and check if you can secure them to something, so to reduce the load on the nipple

i recently messed up a bit with the coolant pipes inside a "mill" : https://www.cnczone.com/forums/okuma...ject-fast.html

i also needed some nipples, reductions, etc, and so i went to buy some : i found some parts that would fit, but actually they were to thin ... in the end, i talked with a guy arround here, and i crafted a stronger part + flame it + zinc layer; i did this, because it is suposed to sustain the weight of all those hoses

all parts that i used are for hidraulic instalations

pls be carefull : if you use T joints, you will put a break on the ( high pressure ) fluid debit ( because of that 90* corner ), but you may not realize this, because it is not easy to be seen; look for round joints this is similar to an end mill that vibrates when taking a sharp corner / kindly

I've never seen an Okuma lathe

hey jim, how fast did you go in that supra ?

only the controller costs as much as a low quality lathe brand; strong design, reliable, few key strokes, few tool corections, abso encoders, safety procedures, and a versatile interface with open arhitecture ( allows custom interface )

if you wish, i would gladly give you a tour, when you reach Antarctica is not about only to see the machine, but to see how it moves (syncronous movements, editable rapids, tolerance parameters, etc), how it can be operated, and things that can be done / kindly

[Jim Dawson]

hey jim, how fast did you go in that supra ?

Huh? supra? I guess I missed something

[deadlykitten]

didn't you said that you tuned a supra to go crazy fast ? ... maybe my memory fails

[Jim Dawson]

Not me. I did build a 200+ MPH '69 Pontiac Firebird many years ago.

[deadlykitten]

ooh, hmm / did it had ( trustfull ) breakes ?

[Jim Dawson]

ooh, hmm / did it had ( trustfull ) breakes ?

Brakes? What brakes?