Carima Nontoxic Resin - Part 2 of 2

Calibrating Carima's "Nontoxic" Resin 

So this is Part 2 of my experience with Carima's Nontoxic resin, focusing this time on calibrating my Saturn 4 Ultra 12k printer for optimal results. If you want to have a read of Part 1 from last week, which focused exclusively on the impact this resin has on air quality and your health, you can find it here. 

Slicer Calibration

As I'm using Linux (Mint) as my primary OS, slicer options are a little more limited than with Windows, but luckily for me the most widely use slicer (and my personal favourite), Lychee, supports Linux and so that's what I'll be using. 

I'll be focusing on the Cones of Calibration V3 model from Table Flip Foundry for printing calibration, as it seems to be the most widely accepted way to dial in your printer/slicer for a specific resin. You can download it, and also read about how to interpret the results, on the Table Flip Foundry website here. In summary, you print the model and then check various aspects of it for dimensional accuracy, as well as ensuring fine details are preserved where expected, tweaking exposure times up/down until you have a perfect print. This, in theory, means you then have the perfect settings for that specific resin and can happily throw any models you like at the printer and it will produce perfect prints every time... Again, that's the theory at least.

We can take a look at the Carima website for some guidence on exposure times, which they have included in a user guide here. This is the table from that guide that is relevant to LCD printers.

You can see there are just a small number of printers here so we're going to have to use this as a very rough initial guide more than anything else. Also, these exposure times are for printing at a 50um layer height (0.05mm) but I'll be printing at 30um (0.03mm) so we'll have to adjust further to allow for that too.

Obviously my Saturn 4 Ultra 12k isn't in this table so I decided to take 7.5 seconds as the approximate median exposure for normal layers and then adjust that down to allow for my much smaller layer height as well as the fact the S4U screen is known to be particularly bright and powerful. So, I decided to start with 4.2 seconds :) I also have very conservative wait times as I don't want that as an added variable when troubleshooting. Here are my resin settings in Lychee slicer for my first attempt.

Printing!

So with the settings above, here are the results below.

The first image shows the "success" side of the cones and the second shows the "failure" side. As you can see we have the start of a couple of success cones, with the malformed cone suggesting underexposure. The failure side shows that the cones have successfully failed :) So, not a bad start I guess. I won't bother testing the Ale in the Mug, or the Sword in the Skull, as I'd like to see more clean success cones first.

So, I upped the normal layer exposure time to 4.7 and left the rest of the settings the same, then kicked off a second print. This is what it produced. 

I can't say I see much improvement... We still have two malformed success cones, and you could even argue the previous attempt was closer to having one full success cone than this latest print. It's worth noting that these two attempts were printed a day apart, with the second day being a full 6 degrees celcius colder. I'm printing in a non-heated shed so this is most likely the explanation as the vat was certainly much colder, and therefore so was the resin. As today is also as cold, I decided to run a heater in the shed for a while to warm things up, then ramped the exposure straight up to 5.8 seconds to see what happens :) 

I know this is a large jump in exposure time but I'll be happy if I see a clearly overexposed print, which I can then work back from. Here is what I got. 

Despite the fresh IPA still dripping off these prints when I took the photos, I think it's still clear to see this is now a very good print. I can't say it's perfect but we do have all success cones complete with delecate connections, as they should be. We also have no complete failure cones. The very last failure cone appears to have the very beginning of a top cone, so I guess this could indicate it's a tiny bit overexposed but it couldn't be more than 0.1 second over, if at all. In general, details seem reasonably sharp so it's looking good. 

After allowing the IPA to evaporate off, I popped the Ale from its supports and it fit neatly into the Mug - not too tight, and definitely not loose. I attempted to pop the sword from its supports too but I broke it in the process, so I wasn't able to test the Atunement block or Skull unfortunately. I think this is due to the resin I'm using, which seems strong but without much flex, rather than an indication of overexposure. I may test that theory another time by reprinting this at 5.6 or 5.7 seconds. 

For now, I've had enough of calibration prints. I think it's close enough so let's finally print something "real"! I am not into mini figures for tabletop games but I know someone who is so I got him to send me two models to print as a test, so they wouldn't go to waste. Using the settings above I dropped both models onto the plate and this is what I got.

For scale, these are only 33mm tall (a standard Lego minifigure is 40mm tall), so they are very small! I used a flash to take the photos to help highlight the details, and they aren't the best photos, but I think you get the idea. While they probably aren't absolutely perfect, I'm happy to say I have this Carima Nontoxic resin pretty well dialed in for the Saturn 4 Ultra 12k so I'll likely run with these settings for future prints. 

Conclusion

Overall, I'm impressed with Carima Nontoxic resin. It's capable of delivering sharp results, cures to a very strong form (with a very tiny amount of flex) so it should be suitable for plenty of applications. As covered in Part 1 of this blog (which you can find here), it appears to produce negligible amounts of TVOCs and absolutely no odour at all. Those are quite a few green ticks in it's favour. 

It's also true that this resin is expensive and it needs more time to cure than "regular" resins, but it is a specialist resin which ticks the most important box for me - it's safer to work with and far less likely to cause any health issues. I won't worry about handing toys to my kids that I've printed with Carima Nontoxic resin, so I guess that says it all.