Two Scales for Z- Axis?

[TZ250]

What is required to install two scales on the Z-axis readout (one for head movement and the other for quill movement)?

Milltronics can do the change, but they charge $1,150!

For that price, I'd install a stand alone digital caliper type readout on the quill.


Thanks guys.

[lakeside]

you will 4 glass scales and a dro that can read 4 inputs one for X Y Z and A (column)

[TZ250]

I should have mentioned that this is a Centurion 6. I'd like to have the fourth glass scale but don't want to pay $1,150.

[lakeside]

$1,150 for a dro and 4 glass scales installed is not a bad price. Do you really need one for column or is this just something you think you need.

[NC Cams]

Bridgeport tried to use a glass scale for the servo and DRO feedback on the Z axis of their EzTrak mills and ultimately had to abandon it.

Seems there was too much hysterisis in the system and they thing tended to oscillate while in servo actuated mode.

They ended up using the scale for the DRO only and a true encoder on the Z servo to get the thing to work properly.

Maybe their problem was trying to do two things (DRO + servo F/B) with the encoder that caused the problem. THat might be why your system supplier wants 2 scales on the axis.

[djs2000]

kk

[TZ250]

$1,150 for a dro and 4 glass scales installed is not a bad price.

$1,150 is for the fourth scale only. It is a 3 axis knee mill and has a normal readout per axis. The Z-axis is the entire head moving up and down, leaving the quill to be free at all times. The quill doesn't have it's own scale. $1,150 is the cost to add a fourth scale to the computer system.

For instance, if the head moves down 4" and the quill moved up 1", the total Z-axis movement would then read 3". Right now the computer doesn't know what the quill is doing.

This is getting to expensive and complicated. I'll just buy a stand alone caliper type scale for the quill.

[One of Many]

I have a suspicion that the only way this could be active is to have the 4th scale add/subtract from actual Z-axis position in the control. That will inevitably place the Z tool zero in jeopardy if the quill is reset. It can also effect the overall Z head travel if the Z were in conflict with soft limits. I suppose Milltronics could display it as a separate readout, but internally it seems like it would require integration.

I have installed a Mitutoyo quill DRO for repeatability between tool changes of drill and endmill changes where required. Nice for manual drill depth or offset surface quick references. I hate cranking the knee, so the head Z-axis is a blessing! The quill connected DRO still can have some coupling slop, but it can be reduced and with a little forethought, rely on accurate movements in one direction. For what? $140 or so, it is well worth the minimal investment rather than adding another bulky glass scale.

Another nice addition is an educated nut for the quill stop screw. When mounting the DRO, leave a bit more room to access the nut button.

DC