
The Elegoo Mars is a DLP 3D printer. It's built around a resin tank with a transparent bottom and a build platform that descends into a resin tank to create parts upside down, layer by layer. The resin is UV active, a UV light sits in the bottom of the machine with a digital display (basically a high-resolution display like it is used in a mobile phone - without the backlight) in between. That display works as a shutter - controlling where the UV light can reach the resin.
On this digital projector screen, an image is displayed of a layer across the entire platform, curing all points simultaneously.
There are many types of UV resins available - most are very toxic (and also smell like superglue) until cured. You need a well-ventilated room and have to make sure that children and animals cannot come into contact with the uncured resin.
By Shawn on Jan 14, 2020, 9:07 AM
Gee should have just waited for your explanation. Better then some I found on-line.

So it is the iris itself that is resin printed, right? Then I assume you hand paint the color on the back. Would a pre-made off the shelf iris work with your eye model for those that don't have a resin printer?
By Tioh on Jan 14, 2020, 1:17 PM

Pupil and iris are indents in the eye model. I made the shape of the iris by subtracting a ball from the eye - the pupil was made by subtracting a disc. That gives it a slight 3d-effect (looks like the pupil is aimed at the viewer). I use 2 component resin to fill the indent after painting - that part is not 3d-printed. The iris has a 16.5mm diameter - I doubt any premade would fit, but I could make another model for that purpose,
The eye can be printed with a normal filament printer too - it's just more work if you want to hide the layer lines by sanding the object.
By Shawn on Jan 15, 2020, 12:41 PM
Got It!

After I posted I was looking closer at the images and was wondering if that was the case. I assume that by printing the eye ball in resin that if you light it from behind that you get a better result also.
I myself have not done much with 3d printing but my house mate is a set designer and uses it for making furniture and elements for their 1/4 scale models. The only big challenge is at that scale you can't get much detail.