UV-Lights and transparent Acrylics

[Durahl (Gaëtan Mahon)]

Not quite related to Lasers but something that just gave me a moment of pause since I now own a 50W CO² Laser…

WAY back when I started Resin 3D Printing, I went ahead and built myself a DIY UV-Curing Chamber using some 395-405nm UV-LED Strips ( at least that’s what the Amazon listing still says ):

As one can see in the above picture I went and installed a transparent Turntable made from thicc™ Acrylic so that the parts could be hit from all directions - Does that thought even work with UV-Light or is it the same as with IR-Light from my CO² Laser getting absorbed by the Acrylic since to IR-Light it appears opaque?

Thanks in advance!

[cggorman (Chris)]

https://www.sanatron.com/blog/optical-transmission-properties-of-acrylic.php

acrylic vacuum chambers cannot be used to detect and measure ultra violet light sources inside the chamber because regular acrylic is not transparent to Ultraviolet light.

400 is right at the boundary between visible violet and invisible true ultra violet. You’d have to look at the specific diode spectrograph to see what percentage is visible, but it’s most likely largely visble. I have some true UV process LEDs and you cannot see when they’re turned on. Honestly not sure if the resin would cure under them or not. I KNOW I wouldn’t want to pay for enough of them to build a curing chamber! Regardless, Acrylic would block ALL that radiation. I don’t know where in that narrow 395-405 band the curing primarily occurs, but it’s a safe bet your platform is blocking the majority of it. Acrylics are popular for conservation picture frame glazing for this reason. It’s naturally UV blocking.

Garden variety plate glass is not. It’s also much cheaper.

[Durahl (Gaëtan Mahon)]

/sigh…

Ah well… So much for that I guess I could chuck the Plate under the CO² Laser and skeletonize it into oblivion for the UV-Light to make it through the then resulting gaps But then again… I’ve been using the System for years like that and it appeared to have kinda served it’s purpose despite not shining through the Plate so… Meh?

Still good to know for future reference! Have my thanks

[LSS (Samuli Samuelsson)]

Hi.

That’s one great looking curing chamber .
A repurposed wine cabinet?

A few years back I was going to repurpose the face tanner unit from an old solarium bed and put it inside an ATA case, but since couldn’t get the first gen. Uniz Slash I bought from a backer as NIB working, I didn’t build the UV curing chamber either .

Since light frequency spectrometers and narrow band detectors are rather expensive and hard to find, there’s a repairpersons trick that is (or at least was before RF TV/video/audio appliance remotes) used extensively when troubleshooting IR remotes.

Haven’t tried with UV, but a cheap digital camera that has no filters will detect pretty far in the IR range.
The better the camera, the better the filters, the poorer the results outside visible range, obviously.

May as well be the optical properties of Your acrylic turntable, but from the pic it does seem that the turntable indeed blocks at least some of the UV.
A straight pic where the turntable blocks some of the leds will remove the optical properties messing up the diagnose.
Unfortunately, unless some more advanced graphic design or photo manipulation software can perform the spectrum analysis from a digital pic, there’s no telling what frequencies/wavelengths are blocked and which pass through.

I was also thinking about a turntable, but mine was going to be a glass one.
Or a mirror .
I worked in the trade briefly, so I would’ve cut it myself.

Since most of the glass used today for windows have all sorts of coatings and additives to manipulate the amount of UV passing in either direction, not everything can be used/repurposed for a curing chamber turntable.

Luckily, there’s a trick for finding out whether there’s a UV block coating or not as well .
Hold a lit match or a lighter close to the surface of the glass, and if both the flame reflections are of the same colour, it’s unlikely that there’s a coating.
Some led lamps/torches work for that trick as well, some don’t.
Generally, incandescent light sources won’t work for that either.

Regards,
Sam

[cggorman (Chris)]

Buy a super cheap 8x10 frame from the dollar store. Just make sure it’s glass glazed, not plastic (probably polystyrene at that price). Pretty much guaranteed no additives, filters, or coatings to get in the way and probably cheaper than the most basic glazing available at the local hardware store. Scary thin tho. Maybe 1-1.5mm? That said, our local hardware stocks plain Jane plate glass in several thicknesses and cuts to size for free. I have never bought a piece that small, but I’d guess it would be well less than $10 for a square foot of 1/8. A cheap diamond file does a nice job of easing the sharp edges. I’ve even used AlOx belt sander. Just use cut resistant gloves and wear those safety specs.

[cggorman (Chris)]

My curing “chamber” uses probably identical LED strips, but I just used a 5-ish gallon galvanized steel pail with a photovoltaic powered turntable. It’s ugly but it was dirt cheap and it works.

Unfortunately, the UV panel on my printer burned out and I haven’t talked myself into replacing it since I’d really rather just get a bigger machine. It’s an old 1st gen Elegoo Mars and most of what I want to print doesn’t fit. Need something more like a Jupiter. Eventually.

[Durahl (Gaëtan Mahon)]

@LSS
That is actually a Custom made MDF Box I back then had commissioned by a Carpenter - Electronics like the PSU / Switches / etc… were then mounted to / hidden behind Plexiglas Plates clad in reflective Sheathing:

System turns on the incredibly noisy Motor when I toggle the Main Switch at the front and Lights turn on when the Door is being closed ( triggering another Switch held in place by a Bicycle Tool in the first Post )

@cggorman
My Resin 3D Printer is a Formlabs Form³ which for the most part I’m digging quite a lot since it has a fairly large build volume of 14.5 x 14.5 x 19.3cm with high Detail due to it not being an MSLA but SLA Model which for the longest time made it the leader in the Market but nowadays it’s basically just an expensive to use Machine as their Resins ( and the Vats ) are expensive AF - Like 200.- per Liter expensive.

And when compared to today’s MSLA Machines it’s also kinda slow but it also still works so me getting a new machine soon is probably not gonna happen.

[LSS (Samuli Samuelsson)]

Hi.

@Durahl

That is actually a Custom made MDF Box I back then had commissioned by a Carpenter

Ok, looks very professional in any case .

@Durahl

System turns on the incredibly noisy Motor

Budget gear reductions tend to be that way .
I would’ve probably used a stepper motor with a simple fixed frequency stepper controller, or a RC motor with a PWM controller.
Those tend to be dead silent, or just whirr a little.

@Durahl

…held in place by a Bicycle Tool in the first Post

I didn’t notice that, I’d probably use a couple of magnets for holding a door like that closed.

Because of my intended primary (and especially secondary ) UV source, my curing chamber would not have had any transparent panels, but for a led source based chamber it’s a different story.
Anything like that looks really nice on the desktop.

Regards,
Sam

[Durahl (Gaëtan Mahon)]

@LSS

I would’ve probably used a stepper motor with a simple fixed frequency stepper controller, or a RC motor with a PWM controller.

These days I’d probably whip up an overly complicated DIY Solution using a spare BLDC Motor / ESC from an UAV I still have lying around and 3D Printing for a custom Gearbox and Turntable in a Case I could now CNC myself

@LSS

I’d probably use a couple of magnets for holding a door like that closed.

The Door does use a Closet Door Magnet to keep it closed. What I meant to say was that the Tool in that shot was used to trigger the LEDs Switch for them to be lit while the Door is open as they’re usually only lit when the Door is closed ( and the Machine being ON ) as the UV-Light is kinda an eyesore to look into.

Back then I needed something sturdy to place the actual Printer on top ( I used to be a bit space constrained )

[LSS (Samuli Samuelsson)]

Hi.

@Durahl

These days I’d probably whip up an overly complicated DIY Solution using a spare BLDC Motor / ESC from an UAV I still have lying around and 3D Printing for a custom Gearbox and Turntable in a Case I could now CNC myself

True, we tend to overcomplicate designs just because we can .
But it’s nice to have toys that we can create parts with, so why not use 'em.

@Durahl

The Door does use a Closet Door Magnet to keep it closed. What I meant to say was that the Tool in that shot was used to trigger the LEDs Switch for them to be lit while the Door is open as they’re usually only lit when the Door is closed ( and the Machine being ON )

I did read that sentence too quickly and misunderstood badly.
Makes perfect sense now, thanks for the clarification.

@Durahl

…the UV-Light is kinda an eyesore to look into.

It sure is, and not that good for eyes either.

@Durahl

Back then I needed something sturdy to place the actual Printer on top ( I used to be a bit space constrained )

Necessity is usually the best mother of invention .

Regards,
Sam