Re: [CAD_CAM_EDM_DRO] Doesnt ANYONE have this drawn up??? was: John's CNC plans???

Jon and Kim, I will check and recheck both theories with regard to my
Old-Dog of a Mill and see if I can use existing stuff or need to modify with
a diff. bearing assy to get that ballscrew held firm. Definitely in the
right direction (with your help), and much thanks to the both of you. Thank
you Kim for the bearing Part number. Might be worth picking one up to see
if it would be a more relyable fit than using the original stuff.. I have
to compare that also to the fact that I only have ONE mill and cant do the
Milling / Modifying of its own parts unless I want to duplicate the parts
and modify the duplicates... That would be a job... :) But might just be
a necessary thing to do.
I'm glad that I now have options that didnt cost me, for Funky Plans that
might not have done me any good... :)

Thanks Friends!!!!!

Vince

----- Original Message -----
From: "Jon Elson" <elson@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Thursday, August 14, 2003 10:12 PM
Subject: Re: [CAD_CAM_EDM_DRO] Doesnt ANYONE have this drawn up??? was:
John's CNC plans???


>
>
> Kim Lux wrote:
>
> >I highly disagree with using existing parts.
> >
> >First of all, the bearings used on the ends of ACME screws generally
> >aren't the sort that would be used on a zero backlash ballscrew setup.
> >The runout, etc. on them is not suitable. In my opinion they need to be
> >replaced with a more suitable bearing, like a 7302, a precision angular
> >contact bearing.
> >
> >Once you realize the need to replace those bearings, the existing
> >bearing holders are useless. Making new bearing mounts also allows the
> >motor to mounted for direct drive.
> >
> >
> >
> The XF-12 bearings in a REAL Bridgeport screw mounting bracket
> (Y axis, and the left X axis) are a matched set of spacer-preloaded
> bearings, and I have tested them, and found them to be BETTER at
> axially constraining the leadscrew than the angular-contact bearing pair
> in my high-precision CNC axis drives. (Due to the size of the ballscrews
> I used, I couldn't use the original bearings.) But, there was NOTHING
> wrong with them, and they would be fine for a ballscrew installation.
> Now, I can't vouch for the bearings in a Rong-Fu or some low-budget
> bridgeport clone from China. Undoubtedly, they are not of the same
> quality.
>
> >Some other thoughts:
> >
> >a) convert as large a machine as you can. The speed with which things
> >can be done on a CNC machine are only limited by the cutting power, so
> >bigger = faster.
> >
> >
> I wholeheartedly agree with this, but not only for the power reason.
> A larger machine is almost certainly stiffer, and therefore can be more
> accurate. Also, the larger machine can accept jobs that the smaller
machine
> has to do in several setups, thereby compromising accuracy.
>
> >b) don't overlook coolant and chip handling. Coolant is an absolute
> >necessity on these machines because the cutting rates are easily
> >adjusted via feed override to be high. Chips will accumulate faster
> >than you can imagine when running multiple parts and high cutting
> >speeds.
> >
> >
> Yup, this is also true. And, I always want to point out that keeping the
> workpiece cool can improve accuracy, and prevent the dreaded
> "ball up" of aluminum on endmills.
>
> Jon
>
>
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