Re: [CAD_CAM_EDM_DRO] .0055 of play in the z-axis

jbordens wrote:

>well after 3 months, i finally have my machine. Overall, i'm pretty
>happy with the Grizzly 3102. The main area that I'm unhappy with is
>the Z-axis downfeed. The fine adjust seems to take a little more
>force to turn than the cracks on the XY table. i'm hoping this will
>losen up with some lubrication. the z-axis also has a bit of lash:
>
>Basically, I've got about .0055" of play according to my indicator.
>This number was obtained by using the fine feed crank to move the
>spindle down mabye 1/2 of the way down. Then, I set the indicator on
>a flat portion of the underside where the collet goes. Next, I press
>firmly upwards from the same place... And the indicator shows a
>little over .005 of movement.
>
>Anyone have any sugestions on how to limit the play between the spur
>gear and the rack? It seems to me like .0055 is an issue that needs
>to be fixed before I start my CNC conversion.
>
>

No proper CNC system uses a coarse rack and pinion on the quill.
Backlash is not the
only concern. Many spur gear profiles do not provide linear movement
precisely
proportional to rotary input. Depending on how the gear was cut, there
may be
cyclical errors in the gear teeth as well.

I would recommend using a screw of some type, and providing a very stiff
linkage
between the nut and the quill.

Jon