Severe Bar Vibration in A20/C-320

[danrudolph]

Maybe someone can point us in the right direction:

We have an A220 with the C-320 barfeed. We have very severe vibration when the pusher reaches 3500mm and continues until 3600mm after that, it is silent until bar change at 3800mm. Our service techs have had it apart 3 times and the issue remains unresolved.

Service tech says that the stationary spindle liner is rubbing the spindle because the bar is whipping inside the liner. We thought it was an alignment issue that the pusher was creating, but after running the pusher into the problem area (3500-3600mm) with no stock and the spindle at 8000RPM, the vibration was not there. So it does appear to be a bar whip issue. We talked about going to a small bar kit, but no one else appears to need them, so why do we?

The bar is 5/16" Delrin in 10' lengths. Barfeed is set to factory parameters. The noise occurs at 8000RPM and 4000RPM (to a lesser extent). We've also seen this problem when we are running Ti in the machine (1/8" dia).

Any ideas are appreciated before this thing rattles itself to death...

[g-code_junkie]

I have found that I have had to "fine tune" the torque settings and others and in some cases tune the servo motor depending on the version of C-320. Plastics and titanium in small diameters like to whip when given 21 mm dia channels to play in especially when not supported by the rollers.You may be able to fine tune the settings or for the best results goto the smaller channel set ,sometimes you can even get away with the 16 mm set.
good luck

[danrudolph]

I turned the collet closed pusher torque down to 1% and the problem persists, although the sound is somewhat different, maybe a little lower frequency.

[cogsman1]

Try adjusting the oil flow. In that feeder too much or too little will cause vibration. There should be a check valve near the pump inside the cover.

[danrudolph]

cogsman,

the oil is not pumping at 3500-3600mm which is about 6 inches before a bar change. the barfeeder is silent at all other positions on the bar.

thanks for the thought though

[g-code_junkie]

Originally Posted by danrudolph cogsman, the oil is not pumping at 3500-3600mm which is about 6 inches before a bar change. the barfeeder is silent at all other positions on the bar. thanks for the thought though

You may also need to drop down the open collet torque.The pusher could be bowing the material during collet open and then returning to following the headstock.

[ProProcess]

I am not familiar with the CAV loaders specifically...
Does it have the "tri-roller" support on the back of the head stock?
If so, the lengths you are specifying sounds like the area your pusher would be transitioning from the loader to the machine.
At that point, some time before, the "tri-roller" would open to allow for the pusher to pass through.
This would cause the vibration untill the pusher made its way into the spindle.
Just some food for thought.
Let us know how you make out.
Good luck!

[g-code_junkie]

The CAV loader has a pushrod servo that is actually an axis of the machine.The C-320 is like a traditional loader that similar to Iemca,FMB,ect..
The CAV loader would be better but unfortunately they can not be put on the Fanuc control.

[danrudolph]

g-code junkie -- we were just talking about the stock bowing tonight, i'll check that out and report back.

with the collet closed torque at 1%, we are seeing almost no "short parts" that we saw at the beginning/end of every bar, the parts would be between .010 and .020" short on the front end. a great improvement right there!

dan

[ImanCarrot]

If it happens at 4K rpm and 8K rpm you may be hitting a harmonic... change the rpm slightly- say 4.5K and 8.5K- does it still happen?

[ProProcess]

Originally Posted by ImanCarrot ... __________________ I love deadlines, I like the whooshing sound they make as they fly by.

Now that's funny.

[dookie2022]

Most barfeeders would give this effect of vibration noises when there is no more support for the bar.
Some barfeeders have a support (suppressor) roller mounted at the most end point of the barfeeder with a support also mounted to the Sliding spindle Z axis and are controlled by the open and close signal from the collet.
If you have support rollers mounted on the spindle the opening of this support stays open is set by a parameter on the barfeeder you can re-adjust this postion but you have to take in account were the Z axis is as the support system may hit the feed pipe under certain conditions.
If this a one off project I would adjust the Z axis in a manner that it would not interfer with the feed pipe when making parts, however it would interfer if you do a zero return or move the Z axis in a position closer to the feed pipe.
There are also barfeeders that can regrip the feed pipe with a different dia adjustment to suit the feed pipe diameter.

There are barfeeders and there are better and great barfeeders.
The barfeeder is the weakest link in the chain and many cannot see the value to get the best