It's not actually UV...

[cliffyk]

I sort of knew this, however while purging image files from my webserver I ran across this one showing the color sensitivity of the human eye:



405 nm light is not Ultra-Violet, but rather just plain ol' visible purple light. actually not all that visible as the sensitivity of our eyes fall off rapidly at wavelengths < 500 nm (and at wavelengths > 680 nm).

It is also not especially harmful to our eyes--and though I would not recommend staring directly at the lamp in our printers for any significant time, an ocassional glance at it will do no harm. It is UV of 265 to 275 nm that causes serious vision issues; UV in sunlight at 310 to 280 nm is what causes "snow blindness"  that can cause eye damage with prolonged exposure. 

However the plain ol' purple light our printers squirt out is relatively harmless--as long a you don't spend hours gazing into its mesmerizing glow you'll be OK. 

The various cautions you'll read about "shielding" your eyes from it, etc. are unfounded. Those espoused by manufacturers and vendors are just plain ol' CYA... 

[Umpa]

This explains it well
http://solar-center.stanford.edu/about/u...nanometers.

[cliffyk]

This explains it well
http://solar-center.stanford.edu/about/u...nanometers.

Yup, that lays it out--405 nm is not UV...

[Umpa]

This explains it well
http://solar-center.stanford.edu/about/u...nanometers.

Yup, that lays it out--405 nm is not UV...

You also should read this. https://www.nature.com/articles/s41598-018-30738-6

[fromFDMtoSLA]

nice infos - THX, but do they have any influence to our resin printing hobby?

[cliffyk]

nice infos - THX, but do they have any influence to our resin printing hobby?

Only that the 405 nm wavelength light used in our printers is not UV...

[Umpa]

I suppose it also means that resins that were made for other systems that do use UV like the Form 1 for example will require crazy exposure times, and might not work at all.

Its not technically UV but you still don't want to be staring at it for any length of time.

I wonder what will be invented in another 5 years - maybe some kind of powder system...

[cliffyk]

I suppose it also means that resins that were made for other systems that do use UV like the Form 1 for example will require crazy exposure times, and might not work at all.

Its not technically UV but you still don't want to be staring at it for any length of time.

I wonder what will be invented in another 5 years - maybe some kind of powder system...

THe Formlabs Form 1 uses a 405 nm violet laser--here are the specs--note that they do not describe it as UV...

[Umpa]

I know the form 1+ had an upgraded laser, but never really looked at what wave length either form1 or + output.

FWIW here is a data sheet for some Makerjuice G+ that we were using at the time - notice the graph how absorbance drops off a cliff towards the 400nm range.

https://cdn.shopify.com/s/files/1/1224/0...9945133065

It might be that they can't make a photosensitive resin that is not 'wideband' so to speak.

Now I tried this G+ in the mars, and the results were not good.

[cliffyk]

I know the form 1+ had an upgraded laser, but never really looked at what wave length either form1 or + output.

FWIW here is a data sheet for some Makerjuice G+ that we were using at the time - notice the graph how absorbance drops off a cliff towards the 400nm range.

https://cdn.shopify.com/s/files/1/1224/0...9945133065

It might be that they can't make a photosensitive resin that is not 'wideband' so to speak.

Now I tried this G+ in the mars, and the results were not good.

Great information, thank you for sharing it. By that graph it is not at all surprising the G+ resin did not work well in the Mars.

Currently the photo-initiators used in 3D Printing resins are by their basic nature "narrow-band" responsive however with chemists being the incurably curious lot they are that might change.

As I have stated elsewhere I suspect selection of the 405 nm curing resin spec for these "happy-homeowner" consumer grade printers was heavily influenced by the relatively benign characteristics of that wavelength. There is no telling what sorts of horror stories would evolve if these machines used 370 nm real UV light...