Transparent perspex signs

[popcornpro]

Ok, in response to my previous post… the term is flame edging acrylic to encapsule a printed matter.

Cheers,

Rich

[Paul Davenport]

Hmmm an interesting one, ill drag out the flame polisher in the morning and give it a go .fingers crossed

[Carrie Brown]

Hi Rich, we do alot of these acrylic signs all with polished edges.

the two ways we do it is…

1. vinyl lettering or graphic to the back, then flame polish the edges, or buy them in already diamond polished.

2. vinyl lettering to the front, etch effect to the back (creating a reall good effect) then polish the edges.

Stephen

[Dave Bruce]

Stephen I take it you mean that you do the polishing yourself? Is it purely flashing a flame over the edges, or is there more to it?

Cheers

Dave

[Andy Gorman]

I think proper flame polishers use some kind of electrolytic process to prevent carbonisation. Or, you can use a buffing mop/wheel. I’ve used one of them little jet flame thingies that have a disposable lighter inside and it worked OK.

[Carrie Brown]

Dave,

Basically what your doing with flame polishing is melting the edge slighty, which then gives it a polished look. we normally do this, but we have some clients that want the best finish, so i get these ones made to size and diamond polished. I would suggest to have a go at flame polishing, do a couple of test runs and see how you get on.

Stephen

[Andy Gorman]

Stephen, Do you use a “proper” flame polisher or do you use something else, like a blowtorch or something. The reason I ask is that polished edges look brillo and I would like to be able to do this myself.

[Rodney Gold]

For the best possible edge , you need to use a diamond polisher , this cannot be beat (Its pretty easy to make one , we used old diamond faced cutter grinding wheels we picked up from the engraving supply guys for nothing , mounted em to a motor and a bracket and a worktable and we just skim the pex across the rotating face of the cutting wheel , we actually have 2 working in tandem , there is a rough wheel for first finishing (its actually carborundum) and then a diamond for the final polish
You must be VERY VERY careful of flame polishing , it induces HUGE amount of stress into the material (ANY heat process does) which is made worse if you use Extruded acrylic (a short molecular chain vs the long chain of cast) add a solvent to the stressed product and it shatters , crazes and cracks develop
Its fine to heat perspex or acrylic in any process so slong as you dont do anything else to it, BUT!!!! The MOMENT you use a solvent based glue , thats when the crazing starts. Even if you clean the item with meths after flaming it , kabloooie – there go the stress cracks!!
You can de stress the pex easily , by leaving it at 80 degreesC (70 for extruded) in an oven for 1 hr per mm of thickness.
If the pex is rough cut , flame polishing is of no use anyway as it cant get rid of chips and rough edges.
You can buy cheap hard steel scrapers that can remove chips and burrs and smooth edges at most perspex suppliers , then you hand sand the edges and then buff using a light tripoli bar and a hard buff at low RPM (You want to avoid heat).
I cannot see how the edges are sealed using heat or a melt , that would be a very messy hit and miss process. There is a machine out there that DOES bond pex to pex by heating the faces of the pex and then running both sheets thru a laminator which then makes the 2 sheets into 1 while encapsulating the item , the machine is about 60k Euros. Other than that , the glueing face to face is most likely what they did . (there is also a optically clear double sided tape called crystalvue – used to mount signs etc inside windows , they could have joined the sheets that way?)
The best glue we have found to use to bond 2 sheets together surface to surface is a degussa product (they vary depending on whether its cast or extruded ) but the generic Degussa (rohm) 2 part Acrifix will give you an optically perfect bond !!!! . When you apply it to the surface , apply it in a X form , then when you push the other piece atop the X , the air and bubbles can escape so you dont get trapped bubbles.

You are going to have another problem when laminating 2 panels and that is stastic , it’s almost impossible to get the surfaces dust free unless you blow ionised air on them.
As to flame polishing , one of those chefs gas blowtorches with a fine nozzle works well , but as I say , there is little point flame polishing if the edge is bad. there are VERY specific blades and geometry used when cutting or milling/drilling perspex , if your supplier cuts with one of these blades , your panel edge is smooth. Alternatively , have the pex laser cut which produces a highly polished edge off the machine.
Flame polishing also “rounds” square edges , thats where a diamond polisher scores. Unfortunately , you cant use the diamond polisher for contoured edges tho – just straight ones

[Carrie Brown]

Great info as always Rodney 😀 I think you’ve covered everything there!!

[Peter Munday]

Rich
I think you are looking at an encapsulated acrylic block, this process is achevied by gluing the two pieces of acrylic together using a resin, this is them placed in a autoclave oven which creates a vacum to release the air bubbles and cook off the liquid resin. the items need to be in the oven for about 24 hours. they are them machined and polished. we used to screenprint all the acrylic awards you see on TV and also most of the beer pump mounts on the bars. There are only about two or three companys doing this type of work in the UK. I know one of the is called Stanley Plastics based in Midhurst, Hampshire but I have no number.

Peter

[popcornpro]

thanks guys!

[popcornpro]

Does anyone know where I can pick up some 3M tape from in the Glasgow area?

I am looking for VHB 3M 25mm x 0.6 x Xm’s for bonding perspex to aluminium hangers.

Cheers,

Rich