Some laser cutting advice needed please

[Andrew N Miller]

Hello,
I am trying to create a part for a scientific instrument. It consists of sticking a micron thick transparent cellulose membrane onto a plastic sheet using a 2 sided adhesive film, in 96 tiny pieces, which is nearly impossible. What I need to do is find a way I can stick a complete sheet of the membrane all over the sheet, and then cut it up in-situ using something like a laser engraver so as to create the seperate bits.

I came across this forum and it seemed better to ask here rather than go to a manufacturer who will just try and sell me a machine.

Does anybody here know if this is possible, to ablate a top layer of cellulose, without cutting right through the plastic sheet (acrylic or ABS) underneath?

Any thoughts or ideas much appreciated.
Regards
Andrew

[Rich Harman]

I think it is doable.

You could vector cut at very low power and then weed (pick out) the pieces. Or you could raster and just vaporize the bits away.

I think vectoring would give the better result. Does it present a problem if there is any marking on the underlying ABS or acrylic sheet? If the plastic sheet has to be absolutely untouched then it may still be possible, but tricky to get the power settings exactly right.

[Rodne Gold]

The best way to do this is to do it the same way as vinyl signs are done , take your membrane , apply a sheet of double sided tape , put it on a waxed/silicon liner , use a vinyl cutter to kiss cut on the liner , weed out the bits you don't want and then use sign vinyl transfer paper to apply the result. I'm sure there plenty video's on youchoob showing how to weed and apply vinyl.
Lasers will affect whats under the cellulose membrane if you try to raster (ablate) it away. You will definately see it with clear acrylic.
You could also apply the cellulose to the object and try to kiss cut it with a laser and weed away what you don't want , but you are likely to see the vector cut lines in the acrylic unless you get it really spot on in terms of power etc. Depends if the outlines of the cut away parts can be seen.....

[Michael Hunter]

I'm about to do something similar - are we working on the same project?

Apply cellulose to adhesive.
Kiss-cut* pieces to the require pattern.
Weed out unwanted stuff, leaving the pieces on the backing sheet.
Using transfer tape, apply all the pieces to the acrylic substrate simultaneously.

* Kiss-cut : vector cut the cellulose and adhesive, but not through the paper backing sheet.

Depending on the size of the pieces, a vinyl sign maker may be able to do this job on a vinyl cutter.
Laser possibly better if the pieces are very small, vinyl cutter probably a cheaper process if the pieces are larger.

[Andrew N Miller]

Thanks for the replies!
This is going to be very low volume, probably a few tens of units, so getting a vinyl cutting die made seems expensive. Ideally I would like to be able to do it on a £500 laser from eBay.

I don't much care if the plastic underneath is marked, as long as it doesn't cut through, because there will be another layer of 3M double sided adhesive placed on top which will hide any marking, and the plastic underneath can be black, although black might make the laser cut it more?

The best solution for me seems to be to remove a thin track (1mm) between pieces, then I don't need to try and peel off any unwanted parts.

Michael, I don't think we are on the same job, but you never know with the chain that these job go through before they get to the person doing the work!

Do you think one of the cheap eBay laser machines would be able to do this?

[Michael Hunter]

You don't necessarily need a die for cutting vinyl - I was thinking of the plotter type machines (which are generally much cheaper than lasers).
Their limitation might be accuracy for very small pieces, as the cutting knife has to swivel in its holder as it goes round corners.

I have not heard anyone say a good word about the very cheap Chinese lasers from ebay - they are not much more than toys.

You would probably be best going to an experienced laserist (preferably a local one) and working with him to get the results that you need, rather than buying a machine and having to learn how to use it first.