Play in linear rail

[cuttergrinder]

We have a mazak vtc-16c mill and it seems to have a little play in the linear rails on the z axis. If I position the head close to the vise, I can move the head side to side about .010 with a bar. The machine also doesn't like very big cutters. We tried to run a 15/16 high speed ball mill and we were only taking about .050 cut and the head just bounces all over. This machine has small linear rails with just small dovetails. Is there a way to snug these rails up?

 

[gregormarwick]

We have a mazak vtc-16c mill and it seems to have a little play in the linear rails on the z axis. If I position the head close to the vise, I can move the head side to side about .010 with a bar. The machine also doesn't like very big cutters. We tried to run a 15/16 high speed ball mill and we were only taking about .050 cut and the head just bounces all over. This machine has small linear rails with just small dovetails. Is there a way to snug these rails up?

Have you checked that the bolts holding the trucks and rails on are all tight? Have you gone round them all, bearing in mind that the problem could be coming from any axis not just Z?

The direct answer to your question is no.

A worn truck will have lost it's preload and will feel very free on the rail, but you might not be able to measure any actual play.
If it's actually loose then it's completely destroyed - broken or missing balls, broken end caps let all the balls out etc.

Assuming you've already checked that the trucks or rails are not loose on the casting, then most likely one or more of the trucks has lost it's balls.

 

[cuttergrinder]

I did more checking and the z axis seems tight but I am getting the motion in the x axis

 

[cuttergrinder]

I can get motion in the x axis with just slight pressure of a bar between head and the vise. The load meter does start to come up though. Could I just be overpowering the x axis servo? The numbers on the screen don't move.

 

[dandrummerman21]

Does it do that everywhere in the x travel?

if you are mounting the indicator on the spindle/z axis, don't pry between the spindle and vise. Push/pry somewhere else. Ideally, if you are trying to isolate where the movement is happening, you would put an indicator on the X rail and push/pull/pry to see how much x is moving left and right. You would do similar in the lateral direction. Then do Y the same way. And finally Z.


Personally I would be looking at the X and Y thrust bearings for play. Then I would also check backlash in the ball nut/screw


Also note: Z axis/spindle movement in the X is usually multiple times higher than the actual movement you'd get from loose rails. If you got .0005" of "lift" at the right rail, for example, and the rails were 12" apart, and you measured 30" from spindle centerline to z axis rails, then I would expect to see around .0015" or so movement in X.

 

[cuttergrinder]

Ill check more after lunch but I can get about .002 in the y but I get about .010 in the x.

 

[cuttergrinder]

The strange thing is it will interpolate a perfectly round hole. I know its not a very robust mill but it seems to me it should run a 15/16 ballmill taking .050 cut

 

[camhead420]

We had 2 Mazaks with linear ways. They really are disposable machines, get what you can out of them then move on.
I'm not sure how much we threw at the first but it got us nowhere.