How do fix the Z vibration on a tri power

[CarlLee]

Hi I picked a used machine and the Z seems to have a lot of vibration which makes the number on the DRO jump around by about .01" Has anyone else seen this problem.

Thanks
Carl

[sharpshooter90]

That can come from a number of sources- Which machine did you buy?
Do you have the Canadian or Korean DRO ?
Our machine had the Korean DRO which has a number of settings- be sure you are on the 0.0004" resolution- the 0.00002" resolution is for higher precision grinders etc.
Mechanically, check your belts for any lumps where they were vulcanized together- we dumped all the Chinese belts and put on Gates and the whole machine was smoother. Look for loose pulleys or mis-aligned pulleys which can cause vibration in the mill head. There is a vertical groove machined in the quill which prevents it from rotating, check the fit of the set screw- if its undersize, the quill can shift back and forth which causes the DRO arm to move.

[CarlLee]

Korean DRO.
0.0002" resolution. I could change it to .0004" but that not going to help much at this point. I will keep it in mind if I get rid of the gross vibration.

Grove and set screw seem pretty tight.
I will look into the belts.
Any other ideas?
Thanks
C.

[digitalmdj]

Are you using the power feed or the hand feed. The gearbox has alot of play in it . They all do and need to be taken apart and shimed. You have to be carful and shim all the gears the same. The bevel gear on the hand feed is a big problem and shound have been taken care of a long time ago. Norvil and I both have the same problem.

[CarlLee]

Could you tell me more about what you shim?
Thanks
c.

[digitalmdj]

Do you have a lot of backlash in your manual feed on your z axis like I do. The gear sounds like it is skipping a tooth. I need to know that to tell if you have the same problem.

[neilw20]

Originally Posted by CarlLee Hi I picked a used machine and the Z seems to have a lot of vibration which makes the number on the DRO jump around by about .01" Has anyone else seen this problem. Thanks Carl

Yes. I have seem this. Does it happen only when the machine is cutting?
I have seen a number of scales mounted off nice square tube attachments.
Tortional rigidity (or the lack thereof) allows the scale mounting to flex.
Place your hand against the scale mounting (if possible), and see if you can fell any vibration. If so fell where the bracket is mounted. If it does not feel the same that might be the problem.
Lot's of readouts have been mounted on angle. Welding or bolting a tube in the angle can fix it. TORTIONAL STIFFNESS RULES!

[digitalmdj]

He is right the tripower mill head is way out there. The support is longer than the older model. When I get to the mill part of my shoptask rebuild I am going to redesign that part of the support. There is one person who has already done that and they have pictures.

[dahui]

I had a thread on this a while back. I've got an '05 bridgemill eldorado and also a bad z axis vibration. The first thing to check is the scale, make sure it's aligned correctly. The second thing is the cable coming out of the top of the scale, a lot of vibration can be transmitted down this metal housed cable. I put a big loop in mine and zip tied it place and it helped a lot. You can also try running Fenner link belts which seem to run more smoothly. Finally, and I think the worst problem, is all of the pulley and belts involved in transmitting the power. Unless all of these are precision balanced and mounted they will generate vibration you will never get rid of.

Take off all the belts and turn on the mill motor. Note the amount of vibration. You could probably balance the pulleys. I never did that on mine, just put in a new motor, precision step pulley, VFD and direct drive to the spindle. I doubt you can get all the vibration out with all that junk whirling around.

Baring major upgrades, paying attention the cable routing on the scale seemed to make the most difference to me. You might also try rubber mounts instead of bolting directly to the machine.

[digitalmdj]

Since it is a tri power the pully bearing may be bad. The pully may need to be balanced also.

[smallblock]

Carl,
Did you find the source of the vibration? I had a little jumping on my Z axis this weekend as well. X and Y are rock solid, so I suspected it was in the mill head vibration. The new Patriot model has a positive belt tensioner via an acme screw that tightens the center ideler- like the lathe. I noticed that the DRO jumping would change with belt tension- belts too loose would cause jump and then it would get better, and then if I put heavy tension it would start to jump again. I noticed that heavy tension would deflect the center idler and cause the belts to be a bit mis aligned. I took Da's advice and put a loop in the cable and got the belt tension to a point where it went away. All of those drive pulleys are heavy cast iron, so balancing could be another issue. When I get a chance I am going to pull them off and take them to my buddy who balance engines and get them checked out.

[digitalmdj]

You might want to try Power Twist® V-Belts. They can reduce vibration caused by the motor.