deviation in perpendicular direction of the ram

[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. In the picture below you can see the trajectory that my tool tip follows.

trajectory.JPG

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,

[PinkertonD]

Hi, Your description is a little confusing and a picture or two would help us. But, reading from that description, are you saying the Ram has two planes of vertical movement? The first is moving the Ram up on the traveling Column, and the second is the Ram cutting head moving within it's slide?

As in the pic, if that is the case, then the cutting head needs to be aligned with the main Ram path.

If that is not the case, can you watch and/or feel the X or Y travel lead screws movng during this process. It may be cross-talk between the axis electronics.

[baitazeare]

What I wanted to show you in the picture above was the top view of the ram moving. It's true that it is a bit confusing, but I hope that you will be able to see my problem better in the picture that I attach you in this reply.

ram_mov.JPG

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.

Looking forward to your help,
Thanks in advance,

[PinkertonD]

OK, I think that is a little more clear. What are you using to move the ram? Are you manually jogging it or using program code?

To me, it looks like you are asking it to Home-to-Start after issuing the Y axis move, followed by an X-axis move.

G90
G92 X0.0 Y0.0
G1 Y6.0
G1 X2.5
G1 X0.0 Y0.0 ; Ignore the X-traverse and go back to G92 Home

When what you are hoping for would be
G90
G92 X0.0 Y0.0
G1 Y6.0
G1 X2.5
G1 Y0.0 ; This would return with X2.5 back to Y0.0 which is what you want?????