Z axis fall-away

[fretsman]

Hi all,

For those of you CNC'ing or adding the iGaging style scales to your machines, how are you dealing with the Z axis "fall-away" when loosening the Z axis?

For example, I have a G0704 (not CNC'd as of yet) and I'm adding the Accuremote scales, and while the X and Y axis were simple, the Z axis concerns me a bit. When unlocking the Z to move it, it does fall away a few thou and I'm wondering what the best way to deal with this is? Do I make a precise fitting "slip-joint" to compensate so the scale reader can drop away a bit when loose? What did you end up doing?

When I go ahead and CNC this down the road, are you just working in the gib and ways so that the Z locks are not even utilized and the axis is just a nice slip fit?

Thanks for looking-
Dave

[PriddyShiddy]

On my X3 I always moved the head Z- before tightening the gib lock. When tightened the tool "raised" up away from the work about .0025"... not a big deal, but since it was very consistent I factored it in when moving if needed.

When manual milling (and wanted high accuracy) I would bring the tool down to a few thou off the work. lock the Z. Place a .001" shim under the tool. loosen the quill. press the tool onto the shim. lock the quill. zero the Z DRO. unlock/move Z to required height and lock again.

Since the DRO was zeroed with the Z locked the offset will be as accurate as I could get it. Also I removed my quill spring... gave me better feel when drilling and more repeatable "weight" on the shim.


FOR CNC you throw the lock handles away. the motor creates the holding torque. Gibs are carefully adjusted to be as tight as possible without inducing lost steps or backlash

[fretsman]

Since the DRO was zeroed with the Z locked the offset will be as accurate as I could get it. Also I removed my quill spring... gave me better feel when drilling and more repeatable "weight" on the shim.

I like the idea of the spring removal, good one, thanks for that.

FOR CNC you throw the lock handles away. the motor creates the holding torque. Gibs are carefully adjusted to be as tight as possible without inducing lost steps or backlash

That's pretty much what I thought, thanks for confirming.

Again, thanks for the reply-
Dave