[rodjava]

Just a thought.....
But what about using 1" or thicker plastics for a cnc router Base/table?

ABS plastics, Polycarbonate sheets, Acrylic sheets or HDPE sheets.

In most cases it would difficult to get full 1" thickness and you would have to laminate 2 or more 1/2" sheets together.

My orginal plan was to use 1/2" al jig plate for the table. Since the design call for a piece 60x36" it would cost quite a bit. I was looking for alternatives which would be as strong and stable as aluminum.

My plans also call for the linear rails for the x gantry to attach underneath the table.

I would like your thoughs, pro and con.

Thank you in advance,

Rod

[vacpress]

I think that depending on what you are planning to cut, and how big the table is to be, a piece of 1" cast acrylic could make a great machine table. The reasons seem to be many.. Mainly accuracy of surface, ease of workability, relative cost, material tolerance...

One fear might be 'creep', after a few years. Another issue is that a piece of aluminum plate with most likely better properties for most machines can be purchased for a similar price as new 1" acrylic.

In my not-that-broad experience with acrylic, 2 'real suppliers', and the hardware stores, I have found that acrylic or similar sheet plastic can be expensive. A 8 x 48 x 1" sheet of acrylic may cost $50 or $60 or more! On the other hand, a 8" x 48 x 1/2" sheet of aluminum is about $60 shipped, on ebay.

I dont know what the larger size for your application would cost, but I think it would be similar. For a table your size, I think even 1" acrylic sheet would probably flex in the center.. Easy to fix up with a few supports.. With supports, I think a large acrylic table would provide an excellent mill surface.. easy to mess up though! I could be generally wrong about the price stuff, but I certainly think thick acrylic plate could be used to make a decent table, and other parts of a machine..

-R

[Madclicker]

I hate "flexi-glas" for machine construction.

[vacpress]

I hate "flexi-glas" for machine construction.

ever work with the stuff 3/4" and over?

[SCHootie]

What about building up a fiberglass table and then milling it flat with the router?
Hope that doesn't sound too stupid.

[vacpress]

Schootie- Have you seen the thread on composite machine base casting? They seem to be well on their way to an admirable collaboration into public research concerning polymers, resins, and other casting processes to create stable machine bases.. I hope they stick with it. They deserve some sponsorship or funding!

Personally, I think the fiberglass would have to be built up very thick, and it would take a long time to dry, and vibrations might still be a problem, but it would probably work for a woodworking machine, or a small machine...

I think I saw a machine with fiberglass parts on here.. Try a forum search.

-R

[SCHootie]

I'm not planning on doing it, I was just responding to the other post. I did read somewhere on here where someone is offering mini mills(or at least frames) made of some kind of concrete polymer material.

[rodjava]

Vacpress,
Thanks for the response.
Could you please explain "creep"? I'm not sure what that means when applied to plastics.

My lowest estimate for a 1/2 x 36x60 T6061 al is about $600. Where are you suggesting I can buy it on Ebay for $60 delivered? I'd buy a ton of it at that price.

My experience with plastics is strictly with delrin and know that I would cost prohibited.

I'm still considering using laminated sheets or single thickness plates of plastics if I find it as a affordable solution.

Rod

[Madclicker]

Vacpress,
Thanks for the response.
Could you please explain "creep"? I'm not sure what that means when applied to plastics.

My lowest estimate for a 1/2 x 36x60 T6061 al is about $600. Where are you suggesting I can buy it on Ebay for $60 delivered? I'd buy a ton of it at that price.

My experience with plastics is strictly with delrin and know that I would cost prohibited.

I'm still considering using laminated sheets or single thickness plates of plastics if I find it as a affordable solution.

Rod

He was talking about a smaller size. Drops are reasonable on ebay, but 36 x 60 would never be considered a drop.

to get 36 x 60 acrylic you would have to buy a full sheet...at least with my plastic supplier. I pay $160 for a sheet of 3/8. I would guess a sheet of 1" would cost at least $500. A 48 x 48 sheet from MSC lists for $370 + shipping.

[vacpress]

oh. the piece i was quoting was what i was recently looking at. it says, above, 8x48x1/2". they are around $50/buy it now, and $10 or 12 shipping.

I found these from... an ebay seller. i will hunt it up and post the store link later...

[wizard]

At work we use a bit of plastic to form "parts" of our machines. Various types too from sheet PVC to acrylics. Some of the reasons have to do with sanitation and salts.

Beyond that most of the plastics I've seen leave a lot to be desired for machine tool parts. I suspect your number one problem with sheet materials, used as described, would be deflection quickly followed by vibration. Some of that could be dealt with by a support frame underneath the plastics and in fact might even be required for aluminum. I suspect that you could get away with a lot less framing with sheet aluminum. I'm not sure how some of the super plastics like Ultem would work or even if you could get it as sheet material. The problem as I see it is that even PVC will be expensive in this application, much less the latest super formulation.

One other huge negative with plastics can be the build up of static. We are talking build ups strong enough to send someone to the hospital, this is not your door knob type of shock. So you end up with a safety issue and a cleaning issue. This can be controlled with ionization.

On top of all these issues you have the problem of dealing with the material mechanically.

All in all I don't think it will be the best choice you could make.

Dave

[rodjava]

Steve,
Thanks for the clarification.
Rod