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Hi all, I'm kind of a CNC newbie.

I've converted my Grizzly G1006 to CNC (Master5/Mach1 and Camtronics
4 axis servo), but the backlash and lead accuracy stink.

I understand I can get decent/cheap screws (.004/ft) from McMaster-
Carr, and use a pair of taper or angular contact bearings for the
drive end.

What I don't quite get is, how do you make a 'anti-backlash' nut
from two regular ball screw nuts? how do you connect them to the
mills existing mount (two screws)... I've read about using a spring
to pre-load, but I cant visualize how that works.

Also, doesn't anybody sell a reasonably priced screw with .100/rev
like a 'regular' mill screw?

Any advice?

Thanks,

Dave S.

--- In CAD_CAM_EDM_DRO@y..., "dspinnett" <dspinnett@y...> wrote:

Hi all, I'm kind of a CNC newbie.

I've converted my Grizzly G1006 to CNC (Master5/Mach1 and

Camtronics

4 axis servo), but the backlash and lead accuracy stink.

I understand I can get decent/cheap screws (.004/ft) from McMaster-
Carr, and use a pair of taper or angular contact bearings for the
drive end.

What I don't quite get is, how do you make a 'anti-backlash' nut
from two regular ball screw nuts? how do you connect them to the
mills existing mount (two screws)... I've read about using a spring
to pre-load, but I cant visualize how that works.

Also, doesn't anybody sell a reasonably priced screw with .100/rev
like a 'regular' mill screw?

Any advice?

Thanks,

Dave S.

Some ballnuts has one end with outside fine treads on it, put both
ballnuts agaist each other and using the adjusting outside nut you
can put pressure on the two ballnuts forcing them to pull apart from
each other thus, preloading them.
sort of split acme nuts.
The springs, takes the adjusting nut place ,and it works ok only for
small loads.

Ball screws are practically anti-backlash, nevertheless,
FYO, you'd basically put the two nuts back-to-back, and
screw them together, until they almost 'bind'. now you have
a backlash-free nut. Of course, you wouldn't really mount
them back-to-back, you'd mount each 'back' to either side
of a mounting plate, and use spring washers to 'pre-load'
the screws, allowing some 'give' under severe pressures,
instead of making it a 'hard' mechanical back-to-back
interface. With a Grizzly, and 0.004"/ft screws, I'd not
bother with the antibacklash, as 'machine slop' coupled
with the 0.004"/ft will be the real test for your system.
'Less'n, of course, you're looking for some REAL accurate
work.

RayHex

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From: dspinnett <dspinnett@...>

Hi all, I'm kind of a CNC newbie.

I've converted my Grizzly G1006 to CNC (Master5/Mach1 and

Camtronics

4 axis servo), but the backlash and lead accuracy stink.

I understand I can get decent/cheap screws (.004/ft) from

McMaster-

Carr, and use a pair of taper or angular contact bearings

for the

drive end.

What I don't quite get is, how do you make a

'anti-backlash' nut

from two regular ball screw nuts? how do you connect them

to the

mills existing mount (two screws)... I've read about

using a spring

to pre-load, but I cant visualize how that works.

Some ballnuts has one end with outside fine treads on it, put both
ballnuts agaist each other and using the adjusting outside nut you
can put pressure on the two ballnuts forcing them to pull apart

from

each other thus, preloading them.
sort of split acme nuts.
The springs, takes the adjusting nut place ,and it works ok only

for

small loads.

Ah, I think get it.

If I went the adjusting nut route, I would thread both ball nuts into
the center coupling nut then mount just one of the ball nuts to the
bed attaching where the original split brass nut went?

If so, should be easy enough.. On the square ball nuts, is there room
to bolt the flat directly through the corners of the body, or do you
always have to have a flange to mount to?

Thanks for the input..

Dave.

Thanks Ray.

My work envelope at one shot is rarely over 6" anyway. Would that
justify .001 screws and anti-backlash? I'd like to be accurate over
6" within a couple thou if practical.

Final goal is to make mini running engines, and probably a full size
engine too. The 'Griz' doesn't seem too bad overall - better quality
that the lathe anyway. (both are brand new).

--- In CAD_CAM_EDM_DRO@y..., "dspinnett" <dspinnett@y...> wrote:

Some ballnuts has one end with outside fine treads on it, put

both

ballnuts agaist each other and using the adjusting outside nut

you

can put pressure on the two ballnuts forcing them to pull apart

from

each other thus, preloading them.
sort of split acme nuts.
The springs, takes the adjusting nut place ,and it works ok only

for

small loads.

Ah, I think get it.

If I went the adjusting nut route, I would thread both ball nuts

into

the center coupling nut then mount just one of the ball nuts to the
bed attaching where the original split brass nut went?

If so, should be easy enough.. On the square ball nuts, is there

room

to bolt the flat directly through the corners of the body, or do

you

always have to have a flange to mount to?

Thanks for the input..

Dave.

I don't know what size ballscrews you need, but technoisel have
ballscrews that have a zero backlash ballnuts, cheaper and easyer to
install than any other ballscrews.
they have it with 16mm od ballscrews, and 25mm od.
I've got three 16mm diameter ballscrews 1m long and three ballnuts
for about $450.00 bucks.
the nuts are split in half, so i just needed to make a square block
with a hole on it for the nut,adjusting is just a matter of tightening
the setscrew and it's all done.
the nut is split axialy not in a cross section.
I'm using it on my minimill and on a 24x24 gantry with good results.