Rhodium plated mirror

I’m interested in purchasing a form 1+, but i’m concerned about reliability. i’ve seen many issues associated with the mirror and laser.

a couple things i’d like to suggest, and maybe someone will try this and it’ll work.

one thing, could a rhodium plated mirror work? rhodium was used to plate the reflectors in spot lights during WWII. it’s ability to withstand high temperatures made it successful.

my other suggestion is related to laser heat dissipation. i’m not an engineer, but i do understand that heat changes the way any material performs. i wonder if cooling the laser with liquid nitrogen could be a solution. refrigerated tractor trailers sometimes use liquid nitrogen for direct refrigeration. regulate the supply of liquid nitrogen, and use a cap tube(s) to deliver low velocity nitrogen cooling. conveniently, this positive pressure might even help keep dust out.

maybe even direct nitro flow over the mirror as well.

i look forward to your thoughts.

Form1 issues cannot be due to overheating, as currents and powers involved are way too small. You typically don’t need cooling until you hit about 200 mW, and even then, a decent block of aluminium with passive cooling will do the job.

While more resilient than glass, rhodium is not a very good choice because of relatively low reflectivity. Aluminium is the way to go, and if coated properly (with a quartz protective layer), should be about as mechanically resistant as glass.

what about just cooling the mirror?

The laser is already clamped to a block of aluminum, so no problem. It barely gets warm. The mirror does not heat up. As long as it is in a climate controlled room, you are good.

isn’t a regular mirror while being produced always a first surface mirror until it gets a protection coat? In this youtube clip is explained how to strip the protection coat off a mirror to get a first surface mirror:

Hey @Dave_Boone - thanks for posting! Looks like you’re already receiving great information here but if you have further questions about running the machine I’m happy to chat on the phone as well at 617-702-8452.


@MarcusKnorr Doing what the video describes will result in a first surface mirror with ZERO protection. Usually, aluminium first surface mirrors are coated with an evaporated (thin) quartz coat. Without it, it would scratch on the very first cleaning attempt.

Cooling a diode laser with liquid nitrogen will at best cause them to shift out of their rated wavelength and at worst the thermal stress from having it poured onto the device would cause premature failures. Supposing for a minute you fixed that, the most likely result of that kind of cooling would be a wavelength shift too far from the rated one to get the resin to cure. Plus liquid nitrogen is not something you can just use in a consumer device for a number of reasons. If you really wanted to cool the laser properly thermoelectric junctions are the way to go but it is unnecessary. Once more going lower than ambient temperatures will cause condensation in most desktop environments that will mess up the optics.

Yes FormLabs initially appeared to have a laser reliability issue with the Form 1 but that seems to have passed for the most part since the release of the Form 1+. I met some of the engineers at the Form 1+ launch party and apparently their laser diode vendor was doing something nutty in the packaging process. FormLabs should have IMHO been doing some accelerated age testing but I bet they have learned that lesson. (If I doubted them I would not have bought a printer after the party)

The mirror issues appear (IMHO) to be from dust landing in the unit. Changing the resin tank mechanism to zero insertion force might help but my background is electronics not mechanical engineering. The simplicity of the current design probably makes it more robust. The only mirror failures that seem to appear on the forum appear to be from people getting stuff on them or improperly cleaning them.

For a cool demo of liquid nitrogen cooling of semiconductors check this out.

And then I looked over at the thread…
“Did anyone else receive a Form1+ with a dead laser?”

… guess I spoke too soon. Still we don’t know how many units they have shipped, thanks to adjective animal serial numbers, so it is not possible to know if this is an acceptable mortality rate. Still…

@EvanFoss — in almost all cases where people have had a completely non-functional laser, it tends to be isolated incidents with cabling or something similar. There are always exceptions, of course, but one of the main changes in the Form 1 vs. Form 1+ was in the laser itself. If you take a look at that thread, you’ll see people are (also) discussing the Form 1. I’m going to go ahead and close that one for now, so that we don’t get more confusion…

For the benefit of people who read these frozen threads in the future please explain why they are being frozen. This is the second time this has happened and if I was not on both threads I would not have known why.

Sure thing — I’ve made a note in that thread, @EvanFoss. Apologies for any confusion, and thanks for the note that you’d like more feedback on such things. I will do so in the future.

Not to be a pill but while we are off topic why was this one closed?
Heavy use of Form1