herky jerky Z

[jay R]

Hi guys. I have another air leak and I think it may be the cause for todays jerky Z.

At the top of the mast, there is a plastic coated cable, coming out of what appears to be a small aluminum(barrel shaped, about an inch in dia, same length give or take)valve. There is an air leak where the cable exits the aluminum valve(?)

As I drop the Z down the leak is less, as I raise Z up it gets worse. When I wiggle the plastic coated cable it gets really bad. The aluminum barrel has a plastic cap on it with two screws. I am wondering, without tearing into things any deeper if any knows what is under the plastic cap, is there an o ring or something?

Thank you

[Jan d.]

That's your counterbalance hissing. The servo motor in Z is NOT designed to hold the Z-axis weight up. It can only accel and decel the mass. So something must hold up the structure: that something is a cable cylinder. The cable is the "rod", if you will. And it must always hiss a little because the air "lubricates" the cable going through the seal.

It may be that the top seal of your cylinder is wearing out. That means that your servo is probably having trouble moving the Z-axis up. It may be OK going down.

You have to call in service on this. The alignment and pressure in the Z counterbalance is critical for your machine's accuracy. In the meantime, try to increase the pressure in you counterbalance slightly. That sometimes helps temporarily (make sure you mark the original pressure so you can always go back). Do not go more than 3 to 4 PSI over the pressure that you have now and make sure to get a service call in. It will only be a matter of time until this gets much worse.


Jan.

[Matthew D. Hoedeman]

That's your counterbalance hissing. The servo motor in Z is NOT designed to hold the Z-axis weight up. It can only accel and decel the mass. So something must hold up the structure: that something is a cable cylinder. The cable is the "rod", if you will.

It may be that the top of your cylinder is worn out. That means that your servo is probably having trouble moving the Z-axis up. It may be OK going down.

You have to call in service on this. The alignment and pressure in the Z counterbalance is critical for your machine's accuracy. In the emantime, try to increase the pressure in you counterbalance slighly. That sometimes helps temporarily (make sure you mark the original pressure so you can always go back). Do not go more than 3 to 4 PSI over the pressure that you have now and make sure to get a service call in. It will only be a matter of time until this gets much worse.


Jan.

It is quite easy to adjust on my machine, you un-lock the Z-axis drive (free-move) and adjust the pressure until the head neither raises or drops while the drive is dis-engaged.

[Jan d.]

I am very sure it is not that easy on the Xcel. It is a known wear item. I have seen them go after a move or even after construction in the CMM room (dust getting caught between the seal and the cable and ripping the seal up).

Jan.

[Matthew D. Hoedeman]

I am very sure it is not that easy on the Xcel. It is a known wear item. I have seen them go after a move or even after construction in the CMM room (dust getting caught between the seal and the cable and ripping the seal up).

Jan.

Mine is a ROD and piston and cylinder, just like a car engine, except it's made out of plastic and aluminium. Still the original after all these years (25+).

[Jan d.]

Oh yes, the Validator. People just loved to hate it. I still find them everywhere. Upgraded with whatever software ever got sold by who-ever.

B&S moved away from that solid piston rod on the Xcel, because they found that the alignment of the rod-type cylinder on the Validator had a negative effect on the overall machine accuracy, especially with Z all the way extended, eventhough it was easy to correct on that machine (as you noted). This effect was completely eliminated with the cable cylinder. Only disadvantages: it hisses (so the machine uses more air) and it is more fragile. But it performs beautifully.


Jan.

[jay R]

That's your counterbalance hissing..... In the meantime, try to increase the pressure in you counterbalance slightly. That sometimes helps temporarily (make sure you mark the original pressure so you can always go back). Do not go more than 3 to 4 PSI over the pressure that you have now and make sure to get a service call in. It will only be a matter of time until this gets much worse......


Jan.

Thanks guys!!

Do I adjust the pressure by turning up the machine pressure overall, or is there a way to just increase the counterbalance pressure?

I am about do for a re-hose as well. I have fixed 11 air leaks to date by clipping the end off the surgical tubing and re-installing. If I turn my machine pressure up any more I will be blowing lines left and right...

Thank you again for your prompt responses!!

Jay

[Matthew D. Hoedeman]

Thanks guys!!

Do I adjust the pressure by turning up the machine pressure overall, or is there a way to just increase the counterbalance pressure?

I am about do for a re-hose as well. I have fixed 11 air leaks to date by clipping the end off the surgical tubing and re-installing. If I turn my machine pressure up any more I will be blowing lines left and right...

Thank you again for your prompt responses!!

Jay

Well, on my machine, there is a seperate air pressure regulator for the counter-balance pressure, it is located at the bottom of the counter-balance. I do not know where yours is. However, you SHOUD have a seperate regulator for this, somewhere. You may have to remove the cover off the z-axis to find it, but I would sure think that there should be one.

[inspector212]

Don't turn up the pressure too much or your Z axis ram will shoot out of the top of the machine and possibly through the roof of the building and possibly into the parking lot and possibly through the windshield of your boss's BMW. Anything is possible on a Friday in the forum.

[jay R]

I have all the covers off of the mast and don't see any pressure regulators on the mast. The cylinder runs thru the main beam for the Z. Maybe I have to remove the wrist and moutning plate to get to it?

The machine works fine for a couple of hours but then gets progressively worse as the day goes on.

[Jan d.]

DON'T REMOVE THE WRIST!!!!! There's a damper down there. There's nothing you can do there. Stay away from it.

I forgot where the regulator is. It must be on the Y carriage somewhere. It is not the main air. It may not have a dial since once it is adjusted, you typically do not have to adjust it.

Move the machine down fast and you ought to hear it release the air.

Also, if you take the cover off, the machine is out of square. So before you do any measurements, put that thing back up again.

Again, don't add too much pressure otherwise the Z will indeed go intercontinental.


Jan.

I have all the covers off of the mast and don't see any pressure regulators on the mast. The cylinder runs thru the main beam for the Z. Maybe I have to remove the wrist and moutning plate to get to it?

The machine works fine for a couple of hours but then gets progressively worse as the day goes on.

[jay R]

Thank you everyone for the help. I am limping along. As stated earlier, it works fine for the first couple of hours in the morning after a good nights sleep I guess, lol.

So, who do ya'all recommend for service? Do I need to call B & S on this? Or is there others suited to this type of repair. Also, am I looking at a calibration again after the repair?

Thanks again everyone!!

[#2#]

Thank you everyone for the help. I am limping along. As stated earlier, it works fine for the first couple of hours in the morning after a good nights sleep I guess, lol.

So, who do ya'all recommend for service? Do I need to call B & S on this? Or is there others suited to this type of repair. Also, am I looking at a calibration again after the repair?

Thanks again everyone!!

Where in Iowa are you located? I would recomend you try someone other that B&S but that is just me. I don't know if productivity quality travels as far as you are but they have always treated me right.

[jay R]

Thanks goodluck, I gave them a call today and after explaining what is going on, they recommended swapping out my joystick first. A while back I had some problems with z axis drift, and someone here, can't remember who know, told me to adjust my pot for the Z. I did that and things worked fine for a while. The guys at the shop you recommended felt that it may have gone to **** completely now. I have one on the shelf and will swap it out.

As always, thank you to everyone for the help on this....twould be nice if it is as simple as that!!

Jay

[rangerboat72]

Thanks goodluck, I gave them a call today and after explaining what is going on, they recommended swapping out my joystick first. A while back I had some problems with z axis drift, and someone here, can't remember who know, told me to adjust my pot for the Z. I did that and things worked fine for a while. The guys at the shop you recommended felt that it may have gone to **** completely now. I have one on the shelf and will swap it out.

As always, thank you to everyone for the help on this....twould be nice if it is as simple as that!!

Jay

Hopefully that is all it is. I had that same thing happen on our 15-20-10 several years ago. It's always nice to have a spare joystick around to play with...