Re: In need of a vacuum system for router with a lot of...

Hi Chris,
I think a lot of us here on this list would love to see a photo of the vacuum clamping used on your cnc router. Probably very helpful to some of us.

Regards
Bob thomas

--- In CAD_CAM_EDM_DRO@yahoogroups.com, CL <datac@l...> wrote:
> JanRwl@A... wrote:
> (snip)
>
> >But I fail to see how this PVC-film "bag" over a surface with vacuum could
> >"work" with a ROUTER eating-up the PVC film! Perhaps someone can explain in
> >"1,2,3" sentences for us dummies???
> >
> I'd be happy to ! First off, the technique you are speaking of is
> commonly referred to as "Vacuum Bagging". It is very popular when
> applying veneers to wood or metal. That situation is a "closed" system,
> where for example, you stick in a block of wood with a piece of glued
> up veneer into a Plasic Bag, seal the bag, turn on the pump, and let the
> bag suck flat, effectively "clamping" the veneer to the wood. 25" of
> vacuum will have more clamping pressure on that part than you can
> imagine. You would not want your hand in that bag! With very flexible
> veneer, you can "bag" parts with multiple contours, apply it to wood,
> plastics and metals. The process has become very popular in Marine and
> Aviation, where hulls and fuselages can be "laid up" just like the old
> Fiberglass way, but, be done in such way that the final product is
> thinner and stronger because all air bubbles have been removed. Yes,
> they put WHOLE Boats in Bags !
>
> The aspect of Vacuum Clamping is different in that one uses a "cavity"
> of evacuation to suck or hold a part to it. Its simple really. Take this
> example. Cut a piece of 1/4" plexiglass 12" square. Drill a 1/8" hole in
> the middle of the plastic. Now, take some "closed cell" 1/4" foam tape,
> like they sell for weatherstriping your home. It has to be a closed
> cell, and most packages clearly tell you if it is. It usually has a
> liner and sticky tape on one side. Take the tape and make a 6" square
> box in the middle of that Plexi. Set that piece of plastic on top of a
> board or any flat surface. Find a way to apply vacuum to the center hole
> from a pump that will deliver 20-28" of vacuum. Usually, you can just
> run some clear reinforced vinyl/pcv tubing to that hole.
>
> I bet you can't pull the rascal apart ! In fact, you could probably
> pull a car out of the ditch of ropes were attached to each part! The
> force or "pull" is directly related to the exposed surface area of the
> vacuum "cavity". It has little or nothing to do with the cavity depth,
> as long as there is a cavity. Bigger is better.
>
> How does this apply to a CNC machine ? Well, with the right "vacuum
> fixtures", you can effectively hold down most any part as long as the
> machining necessary does not overcome the surface areas ability to hold
> an item. Advantages are clear, NO clamps in the way, and if it is
> something that gets done repeatedly, set up is a simple as turning on a
> valve. Many Production shops have purchased premade vacuum fixtures with
> long grooves cut into it, where you place a small rubber O-ring
> material. That o-ring is your seal, creating a cavity.
>
> I've used vacuum for a billion things in my life. A vacuum pump on a
> tank in my Shop is every bit as important as my Air compressor. My CNC
> router has a few strategically placed holes thru the top where I can
> apply vacuum. A simple plastic sheet with a hole in the middle, and Foam
> tape on each side, can hold down just about whatever I need to do, and
> you can remove or replace the top foam as necessary to fit the part. You
> should see what you can do by using slices of large diameter Acrylic
> tubing !!
>
> Vacuum..... Gotta Love it !
>
> Long over my 2-3 sentence limit,
> Chris L