Denford Software & Machines

Using an electronic edge finder held in the machine spindle, the machine does not report the same coordinatesat every contact between the edge finder and the workpiece. However, a dial gauge positioned against the end of the worktable does return to the same position at every contact. Conversely, repeatedly bringing the work table to the same coordinates does not always achieve the same reading from the dial gauge.
The error in position can be of the order of 2 - 3 mm.
Homing the machine sometimes brings about a correction as does rebooting the machine.
The problem appears to be worst on the X axis which has been fitted with a new ball screw & the slide ways have been refurbished.
The machine was made in 1998 and runs DOS software, v2.101.
Any suggestions about where the problem might be are most definitely welcome.

Tight slides?
My Easiturn had a similar problem though not as big an error until I retrofitted it... I never did work out why
Is the wiring original? perhaps interference between the cables

If you have 3mm of error you willeither be able to feel it mechanically or will find the slide has stalled.

First try to pull the slide back and forth. If you can feel movement (backlash) then you have to find where its coming from. It will be in the ballscrew, where the nut fastens to the slide, in the bearing supporting the end of the ballscrew, a slack belt or a loose pully on either the end of the motor or screw.

If you cannot feel the backlash then the chances are the slide is stalling. adjust the slide gibb to free up the motion. You may want to disconnect the ballscrew nut from the slide and pull the slide back and forward while you adjust it to make sure it does not have tight spots.

Good Luck!

Hi,

It is easier to adjust the gibb strips by removing the x axis motor. This allows you to turn the ballsrew by hand as you adjust the gibb strip. If you slacken the gib off & then wind it in you can feel its optimum position. It needs to some risistance but not too much.

If you still have problems you could try rurning contouring off.

You will have to add the line "CONTOUR 0" to the machines option file.
Guess this can be found on your floppy disc. It should be in a file called FANUCMD.OPT (will be the only OPT on disc).
This will slow things down but should stop stalling unless the slides are way out.

Thanks v much for the suggestions. I haven't fixed the problem yet but have certainly found something amiss with the ball screw, it does not feel as smooth as it should, and the slides do feel tight. Hopefully when I follow up in the new year all will be revealed.
All the best guys.