deviation in perpendicular direction 1

[baitazeare]

Hi to everyone,

I have a strange problem with my machining center. I have a horizontal bed type machining centre (traveling column), and I’ve noticed an error when I move the ram.
I move the ram to the outer position (up to the final of the course), and the tool tip goes straight, but when I reverse the direction and I start moving inside the ram, the tool tip has a displacement in the X direction (the direction of the bed), and the tool tip goes inside in an inclined straight line.

The machine tool has a direct drive with a rotary shaft in the ram, and a fixed nut in the carriage. I don’t know if it is an error of guides, a drive problem, if it is because of any existing clearance …
As I think that you have more experience with machine tools than I do, I would like to know whether any of you has noticed any similar problem with any machine tool, and if this is the case, which problem you detected and how did you solve this problem.

Thanks in advance,
Best regards,

 

[MiketheEngineer]

Call the "guy" - the mfg who fixes such things!! Sounds like something got "bent"

 

[baitazeare]

With the explanation I've given you above I think it is not very clear. I hope that you will be able to see my problem better in the picture that I attach you in this reply.

The problem is in the movement of the ram along the slide, the movement in the y axis (see picture). While the ram is moving in the positive y direction it goes straight, the movement is ok. But when I reverse the direction, there is a deviation in x axis and the ram moves back in a stright line, but not in parallel to y axis.

I don't know if I've explained it better this time. I hope so. I don't think that anything is bent. The movements (both) are straight.

Looking forward to your help,
Thanks in advance,

 

[btrueblood]

Whatever bearings/guides control the y-axis motion have a degree of slop, which causes the deviation. Replace or rebuild the guides, or tighten the "gib strip" or its equivalent...

 

[ornerynorsk]

Verify that it does it in both manual jog mode and while running a program. You can write a simple test routine to check it in auto mode. If it only does it one or the other, you have control issues. If it does it in both, it is likely, but not necessarily, mechanical. You can set up indicators to verify that you do not have axis creep on your other axis' (resolver or encoder issues).

As BT mentioned, check your gibs or their equivalent, and also check your spindle quill or ram actuation parts to make sure something has not come loose or has broken causing a side-loading while traveling.

These things can be difficult to track down when an obvious problem does not present itself outrightly.

Good luck.

It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.

 

[BrianE22]

Usually the gibs are looser where most of the machining is being done which is usually near the middle of the travel. Move to both ends of the x axis and see if the problem is as bad.

 

[racookpe1978]

What is your direction of rotation of the machining head with respect tot he travel of the head in +x versus -x.

Manual machining only - I have NOT programmed automatic mills and automatic milling machines! - but I've seen great differences "climbing' in the feed direction compared to the opposite: the "Pull" of the tool differs each way, and so the pressure of the tool against the milling head restraint (both gibb - the sliding machine restraint against xy - and the milling head clamp (milling head rotation restraint) may move more when they resist rotation of the head one way compared to the other direction of feed.

At home, my own (very small, very old) mill performs terribly when I feed opposite hand.

 

[BillPSU]

I have had a similar problem in the past. The problem was the roller pack on the ways had been damaged. The damage was caused by a production error when a 1 1/2" drill was broken by the machine being moved sideways while the drill was inside material. Proving such a problem can be difficult.

Get a precision square and indicators and verify the alignment of the axis. If your machine is as large as shown you will probably need to contact the manufacturer and have them fix the problem. The cost will be substantial if the axis/roller packs have been damaged.