I have been printing with a Kossel Mini delta printer for about 5 years now. I feel I’m fairly experienced by now but I’ve never been 100% happy with the consistency of the Kossel. It’s capable of printing some beautiful stuff but it likes to go out of calibration very easily. I decided I wanted to give a resin printer a go for both high detail parts and faster multi-part prints. With FDM printers the larger the object or the more objects on the build plate the longer the print time. This generally scales with volume as the head has to move across the entire perimeter sometimes multiple times and then fill the shape for additional structural strength. The taller an object is, the more layers required, the wider the object is the longer the head will take to move to create the shape. With a resin printer each layer is “printed” at the same time.This makes the main variables for print time the layer height and the height of the object from the bed. My understanding is that the thinner the layer the less time is required to cure each layer and therefore increasing the fidelity may not increase print time linearly. I haven’t tried anything but the default layer height of 0.05mm but if we assume the cure time scales linearly we would get these results:
Cure time at 0.05mm layer height = 2 seconds.
Cure time at 0.01mm layer height = 0.4 seconds per layer.
This will need testing as I get more confident with the printer. For reference the Kossel prints between 0.1mm and 0.3mm normally. I have had succes printing small things at 0.05mm but as you can might imagine the detail from 0.05mm on the kossel is far less than the resin printer. There is an image that shows the comparison on Day 5. The resin printer in theory can print layers as large as 0.2mm but as the layer size increases the cure time will also increase. I don’t know if printing thicker will increase print strength but again, something to test when I get more confident.
Okay on the main point of the post. At the end of January I decided to actually get a resin printer, opting for the Elegoo Mars 2 Pro for its improved curing time and built in air filtration system and attractive price. Resin printers are generally cheaper than equivalently sized FDM printers because they have far less moving parts and with no need to power heating elements I suspect the electronics themselves may not cost as much. I thought I would cover some successes and failures I’ve had with my Elegoo Mars 2 Pro over the first week.
Day 1 – Setup
I unboxed and setup my printer on the first day. I was too nervous to try a print without some consultation mainly around the cleaning process.
Day 2 – First Print
I gave the resin a really good shake, pouring it into the vat, making sure not to let any drip outside of the vat. I was a little nervous during the print. The sound of the print peeling from the FEP sheet sounds fairly similar to a failing FDM print and every few layers I was looking over to see if I could see anything wrong. One thing I don’t love about resin printing (at least with opaque resin) is that you can’t see how the print is doing until it’s almost finished, at least on smaller prints like minis. I chose to print the demo file, the Elegoo rook model. When the print finished I was glad to see it was fully attached with no apparent layer shift. I attached the bed to the angled drip adapter and waited for the bed to be free of dripping resin. I ran the plastic scraper over the top and edges to try and help speed this up.
Taking the bed off the adapter I placed it over a container to catch the prints should they suddenly pop off. I had trouble removing the print, one cracked as I accidentally leaned on it trying to scrape the print off the bed. I understand that they want a successful print with minimum supports to show the capabilities but when it prints so well attached that you risk unlevelling the bed removing the prints I’m not sure it’s an ideal situation.
Day 4 – D&D Minis
I spent a long time slicing 3 minis that represent some of the characters from my current D&D campaign, a tiefling monk, a gnome rogue and a gnome barbarian. I orientated them to produce what I hoped would be the best balance between short print time, minimal supports and what I hoped would be a good angle. Checking once the build plate was fully out of the vat I could just about see the supports and they looked good. It wasn’t until the print finished that I found something disappointing: one of the models, the gnome barbarian, bases had completely warped, cracking under one of the feet making it impossible for the model to stand up. The other two were more or less fine. The bases were a little warped where they had contacted the supports but not terribly so.
Before printing I had taken the original STLs for the two gnomes and modified them a bit. I added a hood and a face mask to the rogue and increased the length and size of the barbarian’s greataxe. The hood required some sculpting of the original model to get a nice hood shape, unfortunately I hadn’t fully appreciated just how small the model was and the hood was nowhere near thick enough for good contact with the rest of the print causing it to be brittle and flake off in parts. As I needed to reprint the barbarian I decided I would adjust the rogue model some more, thickening up the hood, adjusting it to make sure it definitely made contact with the model in as many places as possible.
Day 5 – Nearly Disastrous
I sliced the tweaked rogue and the barbarian again, this time orientating them a little more steeply, this time only in one axis.
Before starting this print I checked I had enough resin in the vat, that everything was square and generally that the printer was ready to go. As the head dropped I heard a horrifying noise and saw that the build plate was being driven into the edge of the vat. Luckily I was right there to turn the printer off. I reset the printer, raised the build plate and found that I hadn’t fully tightened the build plate onto its strut and it had jiggled forward off the strut. I checked it hadn’t been damaged or damaged the vat, retightened it and restarted the print. I was worried that the plate might not be level but I felt like it wouldn’t be too far out and I felt it was worth a go. A bit nervous that the print would fail I waited for the end results. I was pretty sure that the bed was still level enough, it was very tightly screwed down when I levelled it originally and I hoped the screws had held. Upon completion the prints came out much better. The thin base of the rogue was still a little warped but I felt it was acceptible considering the quality of the rest of it.
Day 7 – Replacement Printer Parts, 1st Serious Failure
My delta printer has been a bit iffy for a while now. One of my working theories is that the replacement carriages I installed, having been printed on the pinter are compounding on top of any existing build inconsistencies. I thought printing some replacements in resin would work well as the size would be more consistent, the parts should be durable enough for testing and printing more replacements even if the resin is more brittle than PLA/ABS. With supports, even though they’re solid they come out to only about 1 gram heavier than the FDM equivalent print.
An hour after the print started and I went to check on the finished result and was saddened to see that only the supports were attached to the bed. I grabbed a soft wooden stirring stick and gently ran it through the resin in the vat, sure enough I could feel some carriage shaped bumps. I emptied the vat, pouring the resin back into the bottle with a nice large funnel fitted with one of the paper filter funnels supplied with the printer. As per the instructions in this video I gently ran my finger under the FEP which allowed the print to peel off. I then gently scrapped the vat with the supplied plastic scraper, making sure to remove any half cured resin bits. Unfortunately I don’t seem to have any photos of the failed print, I guess I was already suited up for resin safety and didn’t want to remove my gloves to take photos.
I replaced the lid, gave the bottle a vigorous shake then repoured the resin with some trepidation. I had noticed some slight dents in the surface of the FEP sheet, probably from when I was scraping the resin out of the vat. I was fairly certain it would be okay but couldn’t be fully sure.
I suspected the supports were too few or too light to support the weight of the part. I had also tried printing the parts flat to the plate and this may have contributed to the failure. I was a little concerned about the peeling force but wanted to try it as I felt it would give the strongest mechanical strength for the application.
Reslicing the file I added a 10° tilt and replaced the supports with heavy supports. It turned out I had used light supports, presumably from when I’d added manual extra supports on the last set of minis. This time the print finished succesfully but taking off the parts off the supports I was disappointed to see that the bottom of the parts had drooped where they connected with the supports. Not ideal as this surface is supposed to be flat as it interfaces with another part. I considered that sanding them down may just do.
Day 8 – Third Times the Charm (Bonus Day)
As I started writing this post on day 8 AND I ended up doing another print I thought I’d sneak in an extra day in to the week.
I wasn’t happy with the quality of the printer parts. I’m sure with some sanding they’d work okay but I wanted to see if I could do better. I rotated them 45° and added more supports where the parts had warped a little. I was a little concerned about the effect this angle would have on the structural rigidity of the parts but my main goal is to get the delta 100% re-calibrated make sure it’s working as intended and then I can print sturdier versions on it, though apart from maybe being a little softer against the screws I suspect they will hold up failry well mechanically. I’m really glad I decided to give this another go as looking at them side by side I can see that the original attempt may not have held up for long before failing, it’s not just the contact points with the supports that were warped.
I hope you enjoyed this post about the start of my journey with resin 3D printing.
Recommendations
One print, I can’t remember which, I managed to drip a piece of resin onto the USB stick as I was mounting the bed to the angled adapter. I cleaned it quickly and ran a UV torch over the surface but I’ve since been a little nervous of handling it ungloved, I’m probably being a little overly cautious.
Get a UV torch to help cure any spills that can’t be cleaned fully. Just be careful not to run it over the vat in the printer by mistake. They’re generally not very high energy so take a lot longer to cure resin but as Uncle Jessy experienced in one of his videos you can still cure the top of a pot of resin.