So, we have all of our safety equipment in line, and we know w’re doing this for fun and to create our own wacky bits and pieces rather than looking for cheap replacements to existing minis. Pour some resin in the tank, and hit print, right? (And note, I am again just talking about Resin Printers, not Filament Printers here!)
Oh no. This is nowhere near that simple.
First, every resin printer screen produces different amounts of UV light. That means the length of time you need to expose each layer of the print will vary depending on your printer, and the condition of the screen. Mono UV printers produce a much stronger light, speeding the prints up considerably.
Next, each brand, type and even colour of resin requires different amounts of UV exposure to set as well. We instantly have two factors affecting the exposure times!
But … it doesn’t end there. Resin printers generally offer a range of quality. Most default to a layer height of 0.05mm. That’s pretty damn good. But most can go to 0.03 or even 0.02. My Elegoo Mars Pro can go to 0.02, but I don’t really see any improvement beyond 0.03. Of course – if you have less resin in a single layer, what does that mean? Yes, the exposure time for each layer needs to be altered again.
So what does the exposure time effect?
Over exposure means that you’ve exposed the resin to the UV light for too long. How can that be a problem? Well, if any UV light bleeds around the edges of the print, you’ll find additional resin at least partially sets too, making parts a little larger than anticipated and losing detail.
Under exposure means that you haven’t exposed the resin to the UV light for long enough! What does that mean? Well, small details may be smaller than expected, or absent entirely, as the entire piece may not have set. You’re also more likely to see layers not sticking to each other properly, as the resin hasn’t fully hardened on the existing parts of the model.
You need to dial your printer in to the right settings for the printer, the layer height, and the specific resin. For very precise work, you might even need to dial it in for batches of the _same_ resin!
Test prints exist – the Ameralabs Town being the best I’m aware of, with a whole slew of guidelines here to help you tweak your printer exposure settings based on printing this cracking wee model. There are other test pieces, but this is particularly good to illustrate a wide range of possible results.
You can also generally get recommended PDFs of exposure times for various resins for a standard 0.05 layer thickness from the resin manufacturers and printer manufacturers, like these for the Elegoo here.
To get up and running, using the standard layer height with the recommended settings from the manufacturer will get you working. It won’t be the best quality you can get, but it’ll work, and get you started. But to move off the defaults, you have to really start learning how to work with test prints. Like the article title says – its a learning curve!