A slide idea was Re: gluing teflon and such - anodizing

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "ballendo" <ballendo@y...>
wrote:

> Dave,
>
> I missed most of this thread so I don't know what size the overall
> machine is...
>
> If the outer square tube has a wall of about 1/4 inch or so, you
> could thread it, say 10-32 and use setscrews against a thicker uhmw
> bearing plate (or metal pad with teflon face) on two of the sides.
> The other 2 would have sheet uhmw/teflon as you already planned...
> Hex nuts outside (on the setscrews) would lock the adjustment.
>
> By allowing for adjustment, you eliminate the reliance on the exact
> size of "typical industrial extrusion" tolerances. The allowable
> tolerance for most aluminum extrusions is bigger than you think.

And

> this technique comes with not too high a price of extra work, IMO.
> I'd do it this way and use tubes with a 1/4 or so difference; o.d.

to

> i.d. Be sure to place the pads/screws near the corners for maximum
> stiffness of the assembly...
>
> Adjust the size and location of the screws and stationary pads to
> meet load vs. friction needs.
>
> Hope this helps,
>
> Ballendo
>
> P.S. depending upon load needs, you may even get by with setscrews
> only. By using a uhmw or teflon tipped s/s. Be careful of cold flow
> of teflon! BTW, I'd not use moglice for this, as I think you'll

have

> more problems.
>
> P.P.S. Even 1/8 wall alum can safely be tapped for 10-32; that's 4
> threads, and many nuts have fewer... Use a roll tap(TRF) to make
> these threads stronger. (A good idea anyway, as there are no chips
> either, in addition to the stronger threads.)

You are correct about the tollerance on extrusions. I had some done
some years ago and they quoted me +/- 0.015" standard. They said
they would hold much better, but depending on the heat and pressure
and.... the extrusion can be different than what you expect.

Regarding threadforming taps, I try to use only threadforming taps in
aluminum. I think it is a nicer thread and it is stronger.

I like the idea of the threads, I might put a collar on the end,
slip in a section of teflon, and then slot the main housing. then I
would be pushing on the housing on the teflon. seems like a bigger
surface for engagement.

The more I think about this, the more I think I'll try a few ways.
it's small enough to play with, and I am thinking I need some
experiance with Moglice before I do my lathe....


Dave

>
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, "turbulatordude"
> <davemucha@j...> wrote:
> > --- In CAD_CAM_EDM_DRO@yahoogroups.com, "snuffman5994"
> <parker@m...>
> > wrote:
> > > --- In CAD_CAM_EDM_DRO@yahoogroups.com, "turbulatordude"
> > > <davemucha@j...> wrote:
> > >
> > > > Of course the first question is surface prep. if teflon is a
> non-
> > > > stick, how do you get it to stick ?
> > >
> > > There is a process we use that is a plasma etch. This enables

you

> > to
> > > bond teflon.
> > >
> > > > am thinking about hard anodizing the aluminum before assembly
> and
> > > > need to find out more about surface conditions. Like, does
> > > anodizing
> > > > raise the surface and make for a rougher surface ?
> > > >
> > >
> > > Hard anodic coatings actually penetrate the aluminum 50%. So if
> you
> > > require a .002" thick hard anodize .001" will penetrate below

the

> > > surface and .001" will be above the surface. The problem you
> could
> > > have is on the corners. Make sure you radius the corners to

avoid

> > > plating build up.
> >
> > Ok, this may be on the fringe of off topic, but the ram Z axis

will

> > be a square aluminum tube, with a sheet of some sort of
> > plastic/polimer/epoxy/stuff (PPES) and then another square tube
> > inside. the inner tube will go up and down and the outter tube
> will
> > be fixed.
> >
> > I was hoping to use a pair of tube with 1/8 difference and insert

a

> > couple pieces of 1/16 of the PPES as the bearing surface. then,
> since
> > the inner would move, make the inner part hard anodized to

decrease

> > the potential of wear.
> >
> > This set-up would lend itself to Moglice as the PPES, but that
> would
> > require more attention to detail.
> >
> > It sound like anodizing will raise the surface, decreasing my 1/8
> > some degree, then whatever adhesive us used, will also decrease

the

> > space even more.
> >
> > am I asking too much from stock products ?
> > would I be better off with Moglice or similar ?
> >
> > Dave