[Smertrios]

When the head on my TAIG is moved up (-Z direction) at 30IPM it sounds fine but when its moved down (+Z direction) at anything over 12IPM there is alot of vibration and the stepper can even stall.

[cartertool]

When the head on my TAIG is moved up (-Z direction) at 30IPM it sounds fine but when its moved down (+Z direction) at anything over 12IPM there is alot of vibration and the stepper can even stall.

Up is +Z and down is -Z

Anyway usually there are problems when moving up because the gib can shift and make the slide tighter, so I haven't heard of any problems when moving the head down...

I assume you are using lube on the ways?
Could be that the gibs are just generally too tight, or too loose, so that there is a binding movement...

I'm running a new z-axis at 30 ipm rapids...

You may want to reduce acceleration or velocity, and maybe play with pulse width (what control software are you using?)

[Smertrios]

I typed the Z directions down wrong for some reason sorry about that as for the TAIG its brand new and dripping with oil running with a Xylotex 4-Axis "box" and mach2 demo. The steppers ate 269oz holding torque and can power the x,y,z no problem well at least no problem except when lowering the head.

[cartertool]

I'm pretty much at a loss - have you taken the z-axis apart at any point?
The reason being that given the mechanics of the mill, down feed should always be easy.

If you swap the leads on the motors (so the z-axis is now powered by the x-axis drive) does the problem still occur

If you swap motors (take the motor off of z and replace with one of the other axis motors) do you still have the problem?

All I can think of is that it's related to the acceleration and velocity and pulsewidth settings in Mach2, try cutting them down and see if it helps (especially acceleration)

Did you buy the mill from me or another dealer, or Taig directly?

With the control off, does the axis feel like it feeds smoothly when fed by hand turning the screw?

I typed the Z directions down wrong for some reason sorry about that as for the TAIG its brand new and dripping with oil running with a Xylotex 4-Axis "box" and mach2 demo. The steppers ate 269oz holding torque and can power the x,y,z no problem well at least no problem except when lowering the head.

[Smertrios]

I think the gibs need to be adjusted or rather tightened up I believe the whole head assembly is tilted so that when its going up the bottom part is being dragged up but when the direction changes the bottom part is pushed and kind of skids when the speed goes above 12.

[cartertool]

I think the gibs need to be adjusted or rather tightened up I believe the whole head assembly is tilted so that when its going up the bottom part is being dragged up but when the direction changes the bottom part is pushed and kind of skids when the speed goes above 12.

It's pretty easy to adjust them. Adjust the clamping shoes first with the motor off the mill, then mount the motor and adjust the tapered gib on the slide.
Here are the two pages that detail most of that:
Some Notes On Setting Up the Taig Milling Machine
and
Some Notes On Setting Up the Taig Milling Machine V2