Re: Digest Number 5

In a message dated 99-05-10 13:34:38 EDT, Andrew Werby writes:

Andrew Werby wrote:

[I believe the "shopbot" system started with a cable system like this, but
abandoned it in favor of rack and pinion gearing, which is less subject to
stretch and more positive.]

If you've seen a ShopBot "in the flesh", you'll understand. I live in Atlanta
and have been going to the Internation Woodworking Shows here for the last
six years. ShopBot is definitely in the shallow end of the gene pool as far
as CNC routers go. Pretty flimsy stuff. So it stands to reason that their
implementation of a tensioned cable arrangement wouldn't work all that well.

Andrew wrote:
[This is something I've been wondering about as well. If these things are
always hanging out covered with lube, it seems like they would be magnets
for dust, which is abundant in machines like this.]

Exactly, if you can avoid exposed lubricants you have gained a large
advantage in a machine of this sort.

Jon wrote:

>>I've tried the "rollers on tubing". It works fine until you get dust under

the rollers and then the dust cakes under the intense pressure. The nice
thing about the BW wheels riding on hardened rod is that the contact area is
so small and hard that it just cuts right through most crap that gets on the
rods.. BW touts the "wiping action" of their wheels on their V track and it
does seem to work reasonably well that way too...

Andrew wrote:
[Perhaps brushes could be mounted in advance of the wheels, to push chips
out of the way?]

Yeah, I've done this and it works to some extent. After the brushes wear a
bit you have to readjust them or dust starts to cake again.

I'm gonna try to take a few pictures of my little CNC router setup. I"ll put
'em on a website and link to it in a message "real soon now". All I have is a
grayscale quickcam so don't expect superb quality.

Jon