TIPS FOR CUTTING ACRYLIC MIRROR...

[ru-alright]

Hi All

Need some tips for cutting silver or gold mirrored acrylic. I recently purchased a HPC LS3020 laser cutting machine. It cuts coloured acrylic upto 4mm very nicely however a bought some silver and gold mirrored 3mm acrylic recently...I have 2 different sorts of silver mirror one has a smooth white backing and the other a grey tape texture. It cuts the white backed silver mirror really well however the grey backed silver and gold mirror burns when lasered and a small flame is produced. Normal acrylic does not burn or produce a flame. Whilst my air assist blows the flame away, the finish is charred and slightly melted.

I would like to purchase more of the white backed stuff in both silver and gold mirror but I don't know exactly what it called.

Also am I actually cutting the grey backed mirror right, 80% power 12 speed works well on normal acrylic but not the grey backed ? Is my air assist enough. Any guidance would be much appreciated...

Regards
Steve

[Rodney Gold]

Its probable that they use different or modified acrylic on one type - often , if its impact resistant ,modifiers are added to the acrylic and mirror also often has a protective layer on the mirror side that gives problems. you want a plastics supplier to give you cast (1st prize) or extruded acrylic mirror . cast will cut and engrave best without issues.

[Litografa]

Be careful with grey backed acrylic - possibly it contain PVC. One of my customers have a lot of problems with laser after cutting of similar acrylic.
Do you know manufacturer name or brand of acrylic?

[Tweakie]

The grey backed (crinkled pattern) mirror I bought in the UK and sold as acrylic turned out to be polycarbonate. Maybe you have some of the same stuff.

Tweakie.

[ru-alright]

Hi
Thanks for all the pointers. I purchased the gold and silver acrylic mirror from an online supplier. It is advertised as acrylic..I don't know the manufacturer without asking.

I can't cut it well enough for my customers. I guess it's got something added to it. Yes Tweakie you describe it very well! It looks like the back of glass mirror, grey with a textured crinkled (duct tape) surface. I guesss it may be polycarbonate.

If I am to be successful in cutting this type of finish I'm assuming I need to ensure that the sheet is made of cast acrylic in mirror finish (thanks Rodney).

I also assume polycarbonate is a no no when it comes to laser cutting with my machine.

Cheers
Steve

[KPBadger]

I too have the same problem with the mirror acrylic - the rough grey backed stuff tends to spark ( such as when the laser hits the aluminium bed in the machine ) i presume due to metallic content . thus the heat generated causes bubbling / charring . its ok on simple outlines but detailed cutting is difficult. i have not seen the white-backed material but will look out for it.

With respect to other colours, particularly black and white:-
I have recently had customers bring my 'acrylic' which has no branding on the protective film. it tends to be very poor when compared to the 'genuine' perspex/plexiglas/repsol materials.
when cut the black melts a lot, and the white bubbles/chars - it behaves more like styrene..... and has a bad smell when cut - which i can only describe a cat pissing grapefruit. yuk!

avoid the unbranded rubbish!

KPB

[Rodney Gold]

Never work on customers unbranded material , if you supply your own you know the quality and settings to use and you make more profit as you can mark up the material, apart from which some materials will harm your machine or the fumes can make you ill.

[ru-alright]

Cheers guys....

I managed to source some white backed silver and gold mirror the other day. It's about everywhere just need to make a few calls to check.

You're right about the grey stuff, once started on a cut it sparks then when moved off that line starts the 'arching' must be something to do with angles of beam etc. It's just OK on cutting something like a heart shape out. The white backed stuff is fine and cuts well for me as 80% amp & 12 speed on my HPC LS3020 laser. I also lift the sheets off the metal cutting bed with 4 scrabble tiles providing space for heat to dissipate and air / fume removal. My back and front of cut acrylic is very neat. I have been leaving the protective film on both sides on the acrylic during the cut. There is a slight rise in fumes however I can remove the film on both sides at the last minute to avoid marking. No acrylic smutt or surface heat marking at all. I never cut without obs! I also have an 8mm thick arylic sheet under the metal bed to absorb any left over reflected laser beam. The height is not far away from spot on for cutting as per manual at 62mm to laser holder top using 3mm.

Cheers

[Rodney Gold]

You can use a piece of black or any other coloured anodised aluminium as a "backstop" , it absorbs and wont reflect laser energy and is less risky than acrylic (which is both expensive and a fire hazzard)

[Alexis Martial]

You just have to cut it upside down, i.e with the coating and metal on top and reasonably strong air assist, focus on top of the surface.
In such configuration not only your cut is neat but you can actually cut faster/with less power than for a same thickness acrylic !
The reason: your laser separate the small metal powder and they fly down helpin in the acrylic cut.

I cut this routinely, mostly 4mm mirror acrylic.

BTW, I'm the exclusive distributor in Singapore of high grade mirror acrylic avail in various colors and with/without textures. Would be happy to provide samples if interested.

I expect to put some pictures of these on my website this week-end if I find the time and finish the ongoing modifications of my laser [argon assist + lens replacement].

Cheers.

[ru-alright]

Hi
Yep, have figured things out now. I can cut the silver on back or front both come out nice as long as it has white backing. The gold mirror with white backing cuts well on front (mirror side) with backing on. Cut it on the white side and for some reason it cuts rough melts etc.

[TurkishDelight]

I too am trying to cut 3mm mirrored acrylic but encountered problems. I know that I should cut from the backside. (The coated side) But when I cut, there is constant sparking and a small flame. I'm cutting at lower power compared to normal acrylic but still it melts and has small bubbles on the edges. The worst part is that the sheet doesn't stay flat and becomes even more bent when there's a part cut out. So when the sheet gets closer to the laser beam, it melts and charrs but doesn't get cut through. I assume the material is of low quality, it's unmarked, no brand, but it's the material I have to work with. Any suggestions?