Vacuum Film Technique - A Quick Explanation

[Brady Watson]

So...From what I gather, reading the last several posts, questions are being posed in this thread by people not actually using the technique from post #1. This is truly amazing to me...

If you use the technique as it was designed & written, then you will not have parts lifting, you will not have sheets curling as they are cut and other issues. I'm sitting here reading, thinking both Steve & Ed are using the VF Technique, and then we are spraying bleeder boards with glue and doing other things...If this is confusing me while reading, then it would not be a stretch for someone new to vacuum to get completely confused, lost and mis-informed.

Correct me if I am wrong in my assumptions.

Like anything else I post up from my own R&D, I only ask in return if you use the technique, share your experience & post pictures for others, further advancing our efforts and progress as a group.

-B

[knight_toolworks]

I want to use your methods. but I don't know if I could bill it. most of what I cut with the spray adhesive has been just simple cheap parts out of thin plastic. but it looks like lexan needs all the help it can get.
but the spray adhesive is dirt cheap and fast.
but as soon as the pressure foot is out I won't need it anymore.
if I ever remember to order the materials i would try it.
I had to cut 8 sheets of 2x4 .03 lexan yesterday. I vacced down some mdf flattened it out and spray both pieces lightly and cut it one sheet after another. I was actually cutting 3ips with a 1/16" bit and never lost a piece. Now this method would not work always and would only work with a straight cut bit.

[woodturner]

Hey Brady,

Let me clarify. I tried the technique on my 3/16 lexan (not acrylic) and as I previously stated, and thought it worked great. I only had one part lift off the tape. Also, remember I had to apply transfer tape directly to the lexan since it was not covered by a protective paper, but rather a "cling" film. I then sprayed contact cement to the back of the transfer tape since we are "set-up" to spray contact and don't stock double sided tape. For what it's worth, I think the spray glue is faster for us, contributing to lower cost.

I am going to try it again tomorrow using thinner (1/8") lexan in the hope of a better finish. I would not have tried either of these without you sharing this technique. If I have better results, I'll share that information as well. What I should have done was start a new thread addresing the machining issues of Lexan.

I don't think my parts (other than the one previously mentioned) moved. I think I have other things at play (X and Y steps rather than true arcs) that I don't really know how to solve. Part of it may be that, since lexan is expensive stuff, I am trying to nest parts as close together as possible, leaving just enough room for the cutter to go by. That obviously means that after the one part if cut, the next path is cutting mostly air. Perhaps this is contributing to chatter. But, again, I did it in two paths with the finish pass cutting around .020. I would think that would "clean it up." I could be wrong and still getting bit deflection.

Lastly, when I responded to Steve about my experience cutting 1/2" lexan, I should have stated that was around six months ago and I had no other plan of attack other than just suck it down with the pump at the time.

I hope that clears it up.

Thanks Again!

Ed

[Brady Watson]

Ed,
Thanks for the feedback. So the spray glue worked fine & didn't bleed thru the transfer tape then? What brand did you use? 3M 77/90 ?

In terms of chatter, make absolutely sure that your motors are fully engaged in the racks (on PRS) - provided that your R&P are greased and relatively new.

Also, make sure you are using the Arcs_Inch post processor instead of the regular Inch one. This will smooth out curves, but not straight diagonals. Of course all of this goes without saying that if you have extra or jagged nodes in the artwork, they would also be a factor.

Thanks!
-B

[woodturner]

Brady,

I will have to check on the contact glue. We buy it in the propane style tanks from our laminate supplier for around $250 per canister. I think this one was from Web-Don (our Wilsonart Supplier).

I am using the arc/mm post. I removed the other posts from my options a long time ago.

My racks are greased, the motors seem tight (I can't move them at all when powered up).

As far as extra or jagged nodes, I am not sure how to tell if that is the problem. As stated previously, I am creating the geometry in Acad LT using lines, fillets, arcs created from three points, offsets, and trimming accordingly. I can "zoom in" all I want and there are no wandering points or anything like that. I do see segemented arcs and angled lines. I had always assumed that was simply the resolution of the graphics and NOT anything that would create a problem with the tool path. Now I am not so sure!

And by the way, I didn't get to run the addtional parts today, but I'm shooting for tomorrow.

[widgetworks_unlimited]

Brady's vacuum film technique has worked well for us in past applications. I'm sure many folks can benefit from having it in their clamping arsenal.

Ironically, a few weeks before Brady first posted to the forum describing this method, I had designed and started using a new "pressure foot" clamping attachment. It allows you to clamp and cut many of the same parts that would require a vacuum film technique, but with our pressure foot you don't need the transfer tape, double-sided tape, or backing material. For many parts you don't even need a vacuum table.

I don't want to sidetrack this discussion away from "vacuum film clamping". If you'd like to hear more about our pressure foot, here's a link to my full post in the product listings section of the forum.

It's been hard as heck to keep quiet - watching this discussion while testing our prototype and getting our first production run of pressure foot attachments ready for sale. I didn't want to discuss them on the forum until I was sure we had something that would provide a real benefit to others.

Here's a sample photo of .010" aluminum that I've wanted to share with the forum for the past 3 months... I was smiling ear to ear when I first cut this - no tabs/post processing required. Ready to go straight off the machine.

- Russ

[Brady Watson]

Looks great, Russ. Thanks for posting.

Know what you mean about keeping quiet during R&D sessions...

Keep up the good work.

-B

[xbinbc]

Thanks so much for this method. I cut a full sheet of 1/4" cast plexi this way today. 6" nested letters. Edge qualiy was excellent, not one letter moved. I have to find a canadian source for the mounting tape. I also had to use spray 77 glue between the transfertape and coroplast. No tabs
& no need to worry about the insides of text flying around!
Totally impressed

Jon Shoring
Signfast Custom Signs
Vancouver Island
Canada

[knight_toolworks]

you got to invest in the pressure foot. I have cut some very small parts and don't loose them. about all I have not been able to cut were these squares that will about 3/8" square. I still need to vac the material down but now I pretty much cut without any extra hold down.

[geneb]

Because the forum software is mis-configured (only allows four image links per post), I've written up what I did when following Brady's technique here:

http://www.geneb.org/shopbot/cutting_alu.html

thnx.

g.