Resin Printers and Tough Resins - Early Thoughts
I just wanted to share my thoughts on resin printers AKA MSLA/LCD printers which recently have become very affordable.
Resin printers' claim to fame is their very high resolution - it is not uncommon to print with 0.05mm layer height whereas 0.2mm is considered on the fine end for a filament printer. This high resolution gives resin prints their very fine details and smooth surfaces - not far off injected parts.
So, why didn't I buy one of these when I first started looking into 3D printers? Well, resin printers were still a tad expensive but worse, the different resin offerings all seemed very brittle and I didn't trust that I could make strong enough parts. So, it was a no go back then and I got myself a "classic" filament printer instead.
But in the past six months or so, a bunch of Chinese manufacturers have gone head over heels into this market and you can now get your hands on a resin printer for about USD 250-300 and equally important there are "tough resins" coming out, too. One that continuously gets mentioned is the Siraya Blu which seems to best PLA and PETG in many tests and sometimes ABS, too. The resins themselves are coming down in price, too. E.g. Siraya Blu is about USD 50 for 1kg.
That coupled with the fact that resin printers have such high resolution that I could probably get smooth o-ring bores in-print with little to no need for secondary machining means I am now seriously considering buying one.
I have seen one mentioning that the resins are quite heat resistant, too. I would expect them to be very accurate, too but would need to research that a tad more.
Finally, I would think resin parts are pretty much 100% homogeneously fused, so the porosity issues I had with my 3D-printed air gun parts leaking through the plastic would hopefully be gone if switching to a resin printer.
On the flip side is the fact that the process is very messy - and that uncured resins may lead to all sorts of potential health issues. Also, the printers are noisy. It's not the type of printer you want to have in a small apartment. Also, you need to add some additional "hardware" like containers and IPA for cleaning the uncured resins off of the parts. E.g. some of the more advanced users seem to be using ultrasonic cleaners, so there's a bit of extra expense there. The parts also need to be post-cured under UV lights - and at least one user reported that curing under elevated temps (in his example 60˚C) make the parts a lot stronger, so a heated UV curing chamber should be considered for structural parts. Again, an added expense.
The build volume is rather small as most of these printers are based of off the same 5.5'' LCD screens, so a normal build volume is around 115 x 65mm in X and Y and then the Z differs a little between brands but is often around 150mm. You can get larger LCD resin printers, but the offerings are still few and instead of paying 300 bucks, you are looking at USD 1400 - 1800. But I suspect the bigger printers will come down in price fairly fast, too.
That said, a part size of 115x65x150mm is still plenty big for the majority of parts I would print for airguns. For example, bulkheads are ø38mm diameter and perhaps 50-60mm tall and nose cones just a few mm bigger in diameter.
Very much as an aside for now, if it is true that a cured resin part can stand a fair amount of heat, then I would consider making molds in resin for carbon fiber parts, and that might be one such use scenario where a bigger printer could come in handy.
There's a lot of info to be had on Youtube about the process and what to consider if thinking of getting one. Often, it is mentioned that a resin printer should perhaps not be your first printer but I think that's most often spelled out as a lot of potential users would be younger people. I think if you are a tad techy, have the space needed and the discipline to take the safety issues seriously, then it would probably still be very doable even for 3D-printing beginners.
The Elegoo Mars and the Anycubic Photon are two out of a handful of printers that often gets mentioned as a good buy, so let's look at some pics of those two.
All of these printers pretty much look, operate and perform the same.
As mentioned, in this price class, they also tend to have almost the same build volume (with a few exceptions). I grabbed some frames from
a comparison video where the creator showed the largest parts an Elegoo and an Anycubic Photon could print:
As for test results for the tough resin (Siraya Blu) here's a video by the
German engineer guy whom I mentioned in a previous post:
I am not 100% sure, but I think in an earlier video of his, he found that for filament prints, he didn't gain much by printing solid parts, so his test parts are now done with infill. And he also did the resin parts with infill. Here are some screen grabs of his test results:
So, in Stefan's test, the tough resin is less strong that PLA and about the same as PETG.
Impact wise, he gets these results:
Discount PP which is extremely ductile and though the resin doesn't get close to ABS, it still beats PLA and PETG handily in this area.
But I also found a test by Phil G who printed the same hooks solid in resin vs. infilled when using filament and in his results, the resin prints stand out way more:
Here's a screen grab of the result of Phil's test results:
What's interesting here is is that the solid resin test hook withstood 140kg of pull which was way higher than any of the filament parts and it had about the same impact strength as PETG which is known to be fairly tough and perhaps slightly ductile (not brittle). I am not sure how much we can compare Phil's and Stefan's tests but either way, I think the Blu resin looks very interesting. And remember, this is still very early days. So far, the emphasis has been on detail rendition for figurines (think Dungeon and Dragons and Baby Yoda) as that is what is perhaps most often printed on these machines, but I think other resin makers will start making tough resins soon
To end this long write-up on a more practical note, one recent part that would have been nice to make on a resin printer was the plastic line release I printed a few posts back. It's small enough to easily fit on the build plate and I would expect to be able to really round the edges in print, hold the tolerances of the holes for the pin and resetting spring and do very little post processing on the parts. Actually, cured resin is supposed to sand really nicely so that's an added bonus. If printed in the tough resin and cured properly, I would think it would have come out stronger than the PLA parts.
