Haas VF 3

manchester · Jan 12, 2003

Does any one have any knowledge on the the nitrogen counter balance on the Haas VF-3. It is supposed to be @1150 but is @1000. When machine is powered down head slowly falls to limit.

WILLEO6709 · Jan 12, 2003

the counter balance is supposed to be just that, a counter balance. It sounds like the ballscew is creeping down from the weight of the head. This may point to a potential ballscrew issue. If you have the ball nut loos from the mount, you should be able to turn it relatively freely, but if you try to spin it, it should stop almost immediately when you let go.as a stop gap measure, you could make a "sawhorse" for shutting the machine down, place it under the spindle whenever you turn the machine off.

manchester · Jan 12, 2003

WILLE06709
do you know what the nitrogen is used for?

[This message has been edited by manchester (edited 01-12-2003).]

J. Jacobs · Jan 13, 2003

What you need to do is call your Haas rep and have them come in refill your nitrogen. I too own a Haas VF-3 and the same thing happened to me. (What year is your machine)?
Jake.

manchester · Jan 13, 2003

J. Jacobs
not sure of year it is a friends machine. Is there any way we can refill nitrogen ourselves?

WILLEO6709 · Jan 13, 2003

I think the nitrogen is used to charge a gas cylinder that counterbalances the weight of the z axis sliding head. The pressure will vary with the type of system used. Basically it is a giant nitrogen spring. I would think the head should not creep down even with a total lack of nitrogen. You should be able to get a high pressure bottle of nitorgen at any welding supply. You may have to go to Haas to get the correct adapter. calling the rep may be a good plan, as I mentioned earlier, I don't think the head should creep even without zero nitrogen pressure. what you may have is a worn out screw or a bad brake in the servo motor. The apparent thing is not always the root of the problem.

J. Jacobs · Jan 13, 2003

Not to my knowledge. I've only had this happen once since we bought the machine new in late 96'. It's probably something to think about?

Hey, Wille. How's your cincinnati's doing, good I hope. Those seimens 2100 controls are nice!
Jake

manchester · Jan 13, 2003

just found out that it only drops when servo is turned off. when machine is powered down it does not drop.

WILLEO6709 · Jan 13, 2003

I have nothing bad to say about my Cincinnati's. They have always done anything reasonable I have wanted them to do. It si only when I make unreasonable assumptions that I get in trouble. The sister plant to me in my day job runs Haas. I think they are decent iron, if they had a 2100 I would consider one.

Rich Carlstedt · Jan 14, 2003

Machine tool makers use nitrogen filled cylinders, just like the gas struts on your trunk lid of your car.
The amount of pressure offsets the weight of the head, usually thru a series of pulleys so that the cylinder displacement does'n change much, and this requires high pressure.The thing you have to know is how much pressure at maximum ? This is a design number and is a comprimise so that rapid speed is not affected by the imbalance of head stock weight versus counterbalance force.
In other words, over pressure can be as bad as under pressure with respeck to rapid speed.
Hope this helps

ufscrap · Jan 14, 2003

The reason Haas uses nitrogen counterbalances is to decrease the load on the servo, and keep the head from falling with servo off. There is no brake on the motor. If the pressure drops in the cylinder the head will fall, due to the almost frictionless ball screw and nut, the weight will turn the screw. If you hit the E-stop and pull on the table it will move as well.
I have several Haas machines, and have had to have the nitrogen refilled from time to time. I think the best thing to do is call your Haas man and have him take care of it. I had a VF-6/50 that was low on pressure, and the head would fall to the table at power-down. We just left the machine powered up until the next time the service man came around. The other thing you might find interesting is what the Z load in the current commands display shows. At a standstill it should read close to zero. If the motor is holding the head up it will have a load on it.
I think that it cost less than $200.00 to fill the dual cylinders on the VF-6/50.

ACEMaintenance · Oct 7, 2016

I have a HAAS VF6. When the machine is powered down the Z axis drifts rite down. When I hit E stop the head drifts rite down. Setting at idle the Z load in the Current Commands is at 15%. My nitrogen tanks are at the correct pressure 1150 psi. Any advise is appreciated.

Speedie · Oct 7, 2016

Replace your cylinders. There is no amount of damage to anything but the cylinders that can allow the head to drop.

TrollTuner · Oct 7, 2016

we are an expensive service call away from the HFO. I have always had a local Hydraulic rebuilder/service shop to come out and charge them. Much cheaper!

Nerdlinger · Oct 7, 2016

manchester said:
WILLE06709
do you know what the nitrogen is used for?

[This message has been edited by manchester (edited 01-12-2003).]

I imagine they use nitrogen because it expands/contracts less per temp change than air. And Rich is right...it's like a garage door spring...it makes the door "weigh" nothing.

Mickey_D · Oct 7, 2016

Nitrogen is used because it permeates though rubber seals slower than most other gasses and it is relatively inert.

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