I figured you guys might like some info to help either further confuse or perhaps interest some of you.
I work with plastics and have for many years and to say it's a funny medium would be an epic understatement.
So here are some fun things to consider (all based on my experience, line of work and research...) when thinking about this thread.
First I should mention that I have tried cutting various keys with a CO2 laser and was unable to induce any kind of discoloration other than a darkening of light keys and at best an "ashing" of dark keys. However it was just a test with someone elses equipement and was not callibrated to do so. Tests were done in normal atmosphere and inert. The other thing to consider is that YAG lasers are typically the ones used for contrast engraving or etching of materials (plastics typically). You can indeed turn black plastic a white-ish color depending on the agitation of the molecules in the plastic and the wavelength used. This is also why YAG as opposed to CO2 lasers are prefered, as YAG has I believe a shorter wavelength lending itself to greater flexiblity in aggitation. You don't necessarily need special plastics to do so, but there are a ridiculous amount of polyblends that may compliment certain techniques.
Ideed as mentioned before (rippy?) lasering materials that have a coating or similar layer is common and some keyboards use this. Especially for backlighting. This is a quick and easy way to get contrast, especially if specialied etching equipment is not available, as this would work with many different methods.
Some plastics lend themselves to being expanded or "blown" this refers to the density of the base plastic. You can extrude or even raise expanded plastics. The technique of lasering a key to bring "UP" ridges and either whitening or darkening plastic fascinates me as I find the calibration needed amazing. The funny thing about plastics is sometimes when you alter the base plastic the end result can have differing reactions to solvents.
Many expanded plastics react more to solvents than their base plastic counterparts. Let's say you spraypaint a piece of regular polycarbonate then you spraypaint two pieces of polycarbonate pieces that were stuck together by melting and "foaming" the platics together. The new joint is likely more vulnerable to the solvents in the spraycan and could fall apart.
This can explain why you could on some keys wipe away legends that have been lasered.
However I have not found this to occur and instead believe if you can wipe away (solvent) the color of the legened on a lasered key, then it was likely filled or stamped with a pigmented medium suseptable to the affects of solvents.
But more often than you would expect the legends are made of a more durable medium than the base plastic (thats usually a good thing)
Here are some common things that you can do to plastic with a laser.
- burn
- soot or "talc"
- foam
- harden
- fuse
- vaporize
- melt
- deform
- cut
Regarding the height of the laser in the video that some people comented on. Some of the new and more advanced systems have tightly focused and constantly controled beams coupled with different pulsing frequencies which lend themselves the ability to cut quickly at a distance. This is especially benificial to cuting plastics that happen to fume and/or flame more. Since lasercutters that have a short throw (cutting distance) can often accumulate deposits on the lens or deterioration from reflections. Aside from having very fast multi axis cnc cutting heads some (like the one in the video) will most likely use a tiny controled miror that will deflect/bounce the laser around the bed area while calculating the the different focusing distances for a consistent cut if needed.
...anywho, just thought you guys would be interested
=)
I put my girlfriend to sleep with such talks, lol =P
