RDWorks Learning Lab 94 copper mirrors A Conclusion

If you own a Chinese laser cutter this little series of videos about me learning how to use the free software provided, may solve the problem of trying to learn from a virtually unreadable manual.
I am nothing to do with RD Works, I am not an instructor and I am no expert. This series will document the essential bits of many hours of trial and error

[DoRC]

When polishing, a figure eight pattern is supposed to be best at canceling out any inconsistencies that hand polishing may introduce.

[DoRC]

Maybe time to setup an electroplating rig and get some silver on those mirrors!

[pjnsn_]

Thanks Russ must have missed that one. I just tried to cut a platter and it shattered. Seems like some maybe earlier ones must have been made from some sort of coated glass, it was an old 40gb drive. Very dangerous to cut. I may try again if I can get a metal platter but as you say just to use as a reserve. Did salvage the magnets to keep my access flap closed, same as in your video.

[ingmarm]

G'day Russ, great to see another video. I'm having a ball with my K40 Chinese ebay wonder. I cleaned the mirrors the other day (for the first time) and the mirror in the head was mouldy and horrible. I've seen this mentioned before by Youtubers. Cleaned it up and made a big difference of course. I'm just waiting on an order from Light Object in the US of a proper air-assist head, gold plated mirror ($15USD) and a new 18mm ZnSe 50.8mm lens ($35USD). So I'm hoping for some improved cutting although for such a cheap device I have no complaints at all. Cheers, ..

[tname]

Good to see you again! Couple of questions. 1. How long will the copper mirrors stay reflective? Do they tarnish quickly? 2. I'm wondering if it would work to cut the copper discs from 25mm copper bar stock on my large. Facing the end would get them pretty flat and almost mirror finished at the right speed and feed. I may give it a try. The process would be much quicker with less material waste

[JohannSwart_JWS]

Hi Russ, you're probably aware of this, but optical reflectivity at infrared wavelength is quite different from visual spectrum. So, polishing copper to appear nice and bright might not necessarily be optimal for IR. I remember in the late 80's working with a 20 kW (!) CO2 industrial laser, which had all its lenses made from solid germanium, which appeared visually to be totally opaque, but obviously very transparent to IR wavelengths. The mirrors were gold plated aluminium blocks, which were very flat. All the optics were water cooled from a chiller, and the continuous laser was modulated by a black anodized mechanical aluminium shutter disk (pneumatically actuated), which was also water cooled. This shutter was inserted somewhere in the primary beam path, which was around 25 mm in diameter before focus. Even unfocused, this beam was enough to melt a brick - before the shutter was installed, this was the only way we could temporarily block the primary beam! This laser cut through just about any metal up to 10mm thick, at linear speeds of around 10mm/s. Best regards - I enjoy your videos!

[patprop]

Russ, What about Those First surface mirrors, that are easily found in those rear projection TV's from the mid-2000's? The Silvering for the front surface mirror is usually aluminum. According to Wiki, Aluminum and used for visible light, where Golf for IR ?

[ruralireland]

Been looking forward to this installment of the copper mirror trials, thanks again for your very in depth investigations. very interesting. Looks like there is no point investing in the 'gold' plated mirrors when moly seems to be the best readily available mirror. I might have a word with a jeweler friend of mine regarding gold plating though, just out of curiosity.

[ChrisMuncy]

For polishing the copper, I would have prefered to see you polish it on a glass plate with possibly diamond paste while moving the copper in a figure 8 pattern. This would have ensured the best possible level surface for reflection and possibly add a few more percentage points of efficiency.

Other than that, a fantastic experiment.

[pjnsn_]

Hi Russ have you seen the video on making mirrors from hard drive platters? I don't know exactly what they are made of but maybe you could have a go. They are very highly polished and very flat for obvious reasons. Keep up the research.

[jameslamb]

Good job Russ, nothing like answering a question you keep asking yourself. Roll on air assist and engraving!

[Peeseebeeb]

I haven't tried it yet but I was thinking of using diamond paste for polishing. There are several ebay listings for a collection of pastes ranging from 0.5 to 10 microns. An 8 tube set costs £6.99 in a size similar to that for heat sink compounds which should be more than enough for 3 small copper mirrors.

As for an anti-tarnish coat, , have you tried the ubiquitous WD40? It works well on silver.

Another thought occurred to me and that is to use the laser machine for the cutting procedure. If you turn the laser off, would it not be fairly easy to use a cutting plate of the right weight attached to the laser head and then run a simple programme to make the figure 8 pattern to be printed over several iterations? Than would certainly help with consistency, especially if you make the mounting point of the plate on an off-centred swivel.

[ottosouta]

I was going to suggest gold plating, and I see I am too late for that. In my previous life in - making microfilm eqiuipment, we used heat filters and cold mirrors to stop film buckle under the heat of halogen bulb. How ancient. It was Schott in Germany who made these multilayer dichroic mirrors, vacuum coating layers of exotic materials. I will try to contact them, if they do these kinds of mirrors.

[Remoteflyer]

Another interesting video Russ. I have found your experiments invaluable since I received my 50w Chinese cutter. I was wondering if you have considered gold electroplating your copper mirrors, or maybe trying gold plating aluminium mirrors?

[JelleBoomstra]

So the procedure to coat copper mirrors with gold is not so bad (it has more reflecitivity), but the examples you had were not lapped/polished to a good enough standard?
You results now are quite impressive, but resorting to commercial parties for the production would make it too expensive again.
I would be very interested in a DIY procedure to lap copper mirrors to say 97% reflectance.

[sethbracken]

OxTools has a whole series about lapping that you may find interesting.

[andyspoo]

What are the standard mirrors these cutters usually have, coated in / made from?

[michalmazur]

I wonder what would happen if you'd golden plated them??

[greenacresfarms]

Are you selling these extra copper mirrors?

[paulrautenbach]

As aluminium oxidises almost immediately it is exposed to air, I guess the reflection figures given for it are for aluminium in an inert gas or vacuum.