Dual Z-axis Machine Examples??

[Zuni]

Didn't have much luck with the forum "search" feature; I'm looking for examples of Fine Line Automation's FLA-300 (or similar) machine with dual z-axis. Has anyone done this (put an additional z-axis carriage on the backside of the gantry)?

Thanks!

--Mark

[jsheerin]

I can't remember seeing one, but you could put them both on the same side by mounting a plate to the bearings and mounting both Z axes to that (instead of directly to the bearings). The trade offs would be that this way would require a larger y axis travel vs back to back requiring a longer x axis for both spindles to cover a given area. For back to back one spindle would also be farther from the y axis bearings. With the side to side mounting you could also more optimally position the spindles between the x axis bearings.

[Zuni]

I think I'll have more travel room to spare in the X direction, hence my wanting to mount it on the back side of the gantry. Plus (and I know this doesn't matter) offsetting along the X-axis seems more elegant than along the Y-axis in my mind.

The beauty of the Fine Line Automation setup is it's versitility, IMO (I don't have one yet, but will order in the next few weeks). I was thinking it would be pretty easy to mount another rail and bearing set to the backside of the gantry, making a mirror image of the front and bridging the front and back together so they moved along the Y-axis simultaneously.

I see that FLA is using a rack and pinion for the Y-axis linear motion setup, so I figure I'll have to go back to a leadscrew setup to have room for the second Z setup.

Of course this second Z axis is a "down the road" thing; I have to learn to crawl before I learn to walk. Just thinking ahead and trying not to re-invent the wheel.

[wcarrothers1]

I'm setting up the dual Z's on my new machine side to side.

I'd say if the second z were on the back it would make bit changes and such pretty tricky or a complete pain in the rear..

b.

[Zuni]

Originally Posted by wcarrothers1 I'm setting up the dual Z's on my new machine side to side. I'd say if the second z were on the back it would make bit changes and such pretty tricky or a complete pain in the rear.. b.

I don't know...I think it depends on whether you have the machine's back up against a wall or other obstacle. Otherwise, I'd think you actually have MORE access for bit changes on the rear Z, since you don't. have to reach over the bed.

Just to clarify, here's what I have in mind. Note that the actual linear motion carriages of the back-to-back Z-axis aren't shown, just the gantry and Z axiz mounts:

[wcarrothers1]

Depends on the machine. Still I'd think it would be more dificult over all having back to back. Least on my machine. Also think about dust collection and if you would be able to move the hose to the other router or have to run 2 hoses or something else.

And last. With out the back side open. Don't forget you will need some space for wire routing or echain. In that rendering I question where you would route that neccessary stuff..

b.


b.

[Zuni]

Originally Posted by wcarrothers1 Also think about dust collection and if you would be able to move the hose to the other router or have to run 2 hoses or something else. And last. With out the back side open. Don't forget you will need some space for wire routing or echain. In that rendering I question where you would route that neccessary stuff..

Hmm...Good points that I hadn't yet considered. Thanks for pointing them out. Lemmie think...

[Zuni]

...And, just to make things more complicated, it would appear that I would have to use some other method to achieve acceptable linear motion on the Y-axis; CNC Router Parts lists 4' as the maximum leadscrew length to avoid whipping. The useable Y span on this machine is 4'.


Is there any such thing as a stationary lead screw and a rotating 5-start nut that can be driven by a timing belt pulley?

[jsheerin]

You can do a 4' travel machine. That's what mine is. I limit the speed to 200ipm to avoid whipping. To try to go faster, I designed a rotating nut a few years ago but decided it wasn't worth building. You could just take a normal antibacklash nut and mount it to a timing belt pulley. The pulley would be mounted to a hollow shaft running in thrust and radial bearings in a block. The pulley would be driven by a motor also mounted to the block. See below. There really isn't much more complexity to this than the regular setup - you're just moving the thrust and radial bearings from the bearing blocks at the ends of the screw to a block that travels with the carriage. However if you go faster you could run into load issues with the nuts (or surface velocity getting too high and causing rapid wear of the nut). I'd just do rack and pinion if it was me.