hi dave...
thanks for the link to this group..
the postings i read were not too interesting to me but i only viewed a
couple...
one was about "american houses wired with 230V or not" and connecting a
lathe to the wifes dryer outlet.
so seems the moderators aren't too fast in banning ot...
i found out the quality of sqare tubing varies widely.
i have seen stock that has slightly bent-in sides (due to the manufacturing
of the round edges).
this is bad. but i have also seen good straight even stock that has sides
that are flat like if ground.
i found tubes too where the welding is ground down i guess, if you let your
finger run across the welded side
you can't feel that it is welded, it is perfectly flat. i don't think these
people can weld so precise and thus i think
it is ground afterwards.
this would make very good rails for cnc....
i also had the following idea:
why not use 2 bearings on the side with the welding seam? so you can use
them slightly off-center and there is no
need to remove the seam completely. i know this increases bearing count but
it also makes spring-loading easier.
how do you think about spring loading some bearings?
do you think this is necessary at all?
i thought first of using four bearings, on on each side of the rail.
the bearings sit on M8 screws.
these screws are hold together by a bigger piece of square tubing (rail
diameter plus at least two times bearing outer).
this bigger tube sits concentric over the rail.
the screws go through holes in the bigger tube.
the upper and one side screw is fixed.
the lower and other side screw sits not in holes but in oblong slits. two
springs at each of the two bearings.
the springs are connected to their screw (inside the bigger tube on the
screw threads or outside on protrusive thread ends)
to make the screw slide in the oblong holes use two washers.
but if you only have one bearing in the center it will not sit parallel if
the springs are not perfectly matched.
i sayd i will make a picture and i will do so but i have no cad at the
moment...
maybe a hand drawing soon...
another thing:
drawer slides i guess:
http://groups.yahoo.com/group/CAD_CAM_EDM_DRO/files/CNC%20Router%20(Dan's%20Plans)
/
and again another thing i thought about:
on one homepage i read the following:
"what i would change if making a cnc again"
one point: "only one spindle for the main axis, centered under the working
area"
the guy used two metric allthreads on both sides and a timing belt to
syncronize.
i am not sure what the best would be.
but if using two syncronized threads you can possibly take out the "floor"
/ working platform of your cnc
and put a bigger part under it. thus increasing the maximum height of
millable item dramatically...
that would be impossible if you use a centered allthread under the plate...
what do you think??
regards
stefan