开云体育

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.

Anyhow, thanks in advance.
Jake

.0055 slop on a new Chinese made knee mill is pretty good. My enco knee
mill came stock with .020 backlash on the Z axis, .010 on the X and .008
on the Y. Since your backlash is that much I would recommend trying one
of those gas springs to take the backlash out. Alternatively you can do
what I did which was to put a servo motor with a 4/1 ratio on the knee.
I have used this set up for about 4 years with no wear and it is easier
than trying to modify power head.
You didn't mention how much backlash was in your XY axis.
Dan

You didn't mention how much backlash was in your XY axis.

A quick estimate is about .005 in each axis. Maybe a little less in
the y-axis.

Any good supplier of metric-bore pullies (with a key notch), or should
I just bore out some english ones? Offhand I'd say I have 16mm
diameter coming off the lead screw with a 5mm wide key. I don't have
my actual pad with the measurements handy.

Anyhow, off to waste some time at the Jets/Vikings game. 4 hours of
my life I won't get back. Heh.

Jake

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