Calling all hydraulic experts: Help diagnosing overload problem?

I have a Hardinge Conquest T42 with hydraulic collet closers on both main- and sub-spindles. The subspindle appears to operate fine, but when I open the main subspindle, I end up with motor overload, large pressure drop, and the collet OPEN pressure won't exceed 200 psi no matter what the closed pressure is set to (I can set the collet to 500psi, but it will drop to 200psi when opened.)

Symptoms:

1. Increased load on the motor - goes from 2.5A/ph steady-state (closed) to 4.3A/ph when opened. FLA on nameplate is 3.4A/ph. This is the primary concern. Any program that needs the main to be open (during second-half of operations) will eventually burn out the motor or at least trip the breaker.

2. Pressure drops and stays there when main collet is open. The higher the collet pressure, the greater the drop. I can set the pressure to 500psi, and it will still drop to 200psi when the collet opens.

3. At the same time, the system pressure drops too. It will drop in proportion as the collet pressure is increased. At a collet pressure of 200psi, the system will drop by 60psi. If I crank up the collet pressure way up to 500 psi, the system pressure will drop by 200 psi.

4. The return line on the main spindle in the closed position shows a "glug-glug" of fluid returning. When the collet is open, the fluid moves far faster, and eventually, shows bubbles. Popping the fill cap and looking inside also shows lots of bubbling.


This is what I have done so far:

1. I have changed the fluid for Mobile DTE 10 Excel 32 (the present equivalent to DTE-13M as stated in the Hardinge maint manual.) It was pretty dirty inside - the filter had some large shellac particles INSIDE the filter, around the outside of hte filter, and in the tank. The tank also revealed two tiny threads of black material - possibly sealant, part of an o-ring, garbage left from previous maintenance, not sure. Will need to go back and sift through the refuse oil to recover it. Could be something, but also might be nothing.

2. I have changed the filter. The red bypass button now stays down provided my collet pressure is kept at 200. If collet pressure is higher, the button stays down in the closed position but will pop (and stay up) when the collet is open.

3. I have swapped the spool valves between the main and subspindles. The problem did not follow, meaning the spool valves don't appear to be the issue.)

4. I checked the pressure switch for the open position - it was gummed up with shellac, but still functioned. I cleaned it out with a solvent and replaced. No improvement. I believe the switch is working as it should.

5. I have bled the collet-open line going into the closer - I am getting clear fluid going into the closer (no air.)

6. I can't really see any air ingress along the lines - they look tight, and don't leak.

7. Hardinge suggested "dead-heading" the collet lines to see if the problem changes. It did. With the lines capped, the hydraulic system behaves normally - no pressure drop, no increased load, no pressure change (other than the instantaneous pressure variation of the spool-values shifting. State of collet closed and collet open are the same now. Lovely... this means the problem is in the closer.

I am looking at the drawing of the closer and it appears to be somewhat servicable. Has anyone pulled theirs apart? I'm going to remove the closer and start with the cartridge lock valves. Anyone have any advice?

If the closer operates normally in the closed position, I should look for seals, check valves, etc. that would be engaged in the open position. Either this, or I send it back to Hardinge for an incredibly expensive rebuild. I'd like to be sure it's broken before sending it back.

ADVICE PLEASE. Anyone experience issues like these? What was the cure?

Have you switched the lines to the collet closer?

Closed is now collet open position. Do you have the problem there?

Bill

I am having this exact problem but in reverse when the main collet is closed! Have you found the solution to this yet? I am also looking at the cartridge lock valves in the collet closer but am having trouble getting them out.

I have not found a solution. I have reduced the pressure, and therefore the load on the motor, and at least for now the breaker doesn’t trip. In the long run, only the motor is at risk and as it happens, Hardinge sells the Leeson motors for $750 or so.

The trick to getting the cartridge valves out is to first remove the spacer and the first two o-rings, then put the plug back in and cycle the closer. The back-pressure will push out the valve (if it happens to be stuck.)

I fashioned an aluminum dowel with reduced end then press-fitted a circular neodymium magnet onto the end and used that to pull the valve out the rest of the way.

One of the valves was quite gummed up with shellac which I removed with acetone ( Note: I confirmed with the manufacturer that acetone was compatible with the valve seat.)

I *think* I got a slight improvement in the system, but it wasn’t nearly enough to fix it.

I then tested each valve using a syringe with some hydraulic oil to see if it would block the reverse flow. One of my valves had an ever-so-slight leak which I thought would be amplified under pressure, but after swapping them (no change), I ended up buying a new valve which turned out to be a waste of $260... again, no change to the performance.

It seems that something else is wrong with the closer, but not worth the $4000 Hardinge wants to overhaul the closer.

I had contemplated taking the closer apart, but I’ve been told the collar holding the bearings is fixed in place with loctite and needs to be heated to be removed. If it were not working at all, I’d go to town on it, but not now. Perhaps in the future.

I would be very interested to know what progress you make on yours.

Sorry I couldn’t offer you a solution.


Torin...

To anyone reading this I had this problem and found junk in my lock valves in my collet closer. Cleaned them and fixed the problem. Cheers

Hey Torin just saw your response. I was able to get them out using about the same method you used, a magnet and the hydraulics. I found a chunk of brass stuck inside one of the valves which I removed and seemed to solve my problem - after reinstalling it my system pressure didn't change with the collet open or closed. That didn't last though for some reason it's back to about the same way it was.

Interesting that swapping the valves didn't help you. Did you ever try replacing the o-rings on yours? I noticed the side that works well that the o-rings seem like they are in much better shape. They're sort of triangular to match up with the chamfers on the spacer/valve. The o-rings on the faulty side look quite deformed. Maybe that could have some effect.

Indeed, I replaced all six o-rings and it had no effect. Something else inside the closer is allowing oil to bypass when the collet is open.

Good to hear you made some progress, but unfortunate you found a metal fragment... could it be that another piece of metal has migrated into one of the lock valve?