Laser cutting CD or DVD

[Kris]

Just out of interest, has anyone tried cutting a round blank cdr into a credit card sized CD using the laser cutter and then (successfully) writing to it?
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[Gav]

No, but that's an interesting idea. Might want to check the CD with the 'copper test' first, to make sure it doesn't contain chlorine anywhere. I'm quite curious to see if it can be done successfully. 

The CD is made from polycarbonate, so it'll make an amount of smoke roughly equivalent to the dark genie in Disney movies, but if we're only a small cut and vent it out before opening we can avoid a riot in the space.

Cheers,

Gavi n

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[Luke Emrose]

What I would be worried about the most is warping from the heat propagating across the surface that stopping it from being flat.

I'd be very curious what you find however.

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[chris bate]

i'm getting a picture in my head of my parents cat cocking his head sideways at me as if to say "don't do it" 

from what i'm told cutting a cd will certainly work however the danger is not only the smoke it'll make but the beam reflecting back up and doing damage to the laser,

http://www.youtube.com/watch?v=BcP4YyONitc

[Kris]

Why wouldn't you cut it reflective facing down?
I thought centering it would be a problem, depends if the blank data on a CD is arranged in tracks or is justa 'field' of writable points

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[chris bate]

it aparently doesn't matter if it's facing shiny side down the moment the laser gets through the painted side it's still shiney under there,

centering shouldn't be any problem,  just push it into a corner frame of the honey comb bed the work out where the centre should be with a ruler,

[Gav]

There will be a slight difference for shiny side up or down, with down being slightly better. The clear (to our eyes) plastic is opaque to the laser and will absorb the beam and melt/burn. By the time it's melted down to the reflective side the contacting plastic will be more than hot enough to destroy the thin layer of reflective film, even if it were capable of reflecting the beam back perfectly. 

In practice, we've cut acrylics with reflective film on them before, and also things like thin aluminium foil without issue. 

Cheers,

Gavin 

[Pauline Koh]

Whenever I cut the single side mirror finished acrylic, i've kept the sticky protective film on that the plastic ships in, and also cut with the reflective side down.  

Like Gav said, hasn't been an issue.

that being said, there's no way the cracked water cooling jacket was damaged from the mirrors bouncing reflected laser back up the system from the aluminium foil tests is there?

I'm just conspiracy theorising here.

-Pauline

[Nick Johnson]

Given that the laser requires focusing to do anything useful, any return beam is going to be extremely diffuse by the time it gets back to the tube. It seems unlikely to me that it'd cause any damage even if it weren't diffused - it's just more photons to excite the gas in the tube.

-Nick

[Gav]

Good point, Pauline. I think though, it's too tricky for it to bounce back from that foil and damage the tube. Actually, come to think of it if it were reflecting back a significant amount then it wouldn't have cut the acrylic. Might have been reflecting a bit, and it was that extra level that broke the camel's back, but I'd wager it's unlikely. 

I'm guessing the tube got broken from general wear and tear. They've got a finite lifetime and ours lasted us a few years, and even through the move of the space so I'm pretty happy with it. 

That reminds me, I must order the replacement from ebay...

Cheers,

Gavin