rigidity for router rails

JanRwl@... wrote:

> Gawrsch, it's been 15 years ago when I built a 5 x 10' - "2½ axis" router/X-Y
> Drill for a firm in England. ... SO? Word is: RIGIDITY!
>

Hear hear. Couldn't agree with you more.

But also, rigidity costs money, so I am trying to reach a compromise
where the basic (1.5" dia stainless steel tubes and 1" dia Acme
leadscrew)
can be assembled with composite wood 'end plates', but later can be
upgraded with aluminum or steel endplates (as the finances and/or
capabilities allow).

>
> Remember: Rigidity is what you describe you need, not
> wobbly, barely-holding-its-own-weight tinker-toy stuff!
>
> Rack and pinion or timing-gear belting? MY opinion? Maybe OK for this
> application, but LEAD-SCREWS, even ACME, seem a better choice to me! (See
> top line again!) I'm serious!

> The PTFE-lined linear bearings, a "substitute" for same-size linear
> ball-bearings might be just fine for such an application. Would probably
> defeat "dust problem"!

Yes, I am using UHMW: it is self lubricating and tends to not be
affected by (wood) dust. As the rails are only supported at the ends
(thus making a sort of I-beam) covering the tubes and screws by 'plastic
bellows'
is also a possibility (ie cheap 2" dia air ducting bought at Home Depot)
which might allow such a system to be used in a 'dirty' environment,
such as plasma cutting and flood cooled aluminum milling.

Doug Fortune
http://www.cncKITS.com