Resin 3D printing hurdles

[Bellerophon]

Cutting to the chase, what best practices should I be following with my 3D printer?

I was going to start a thread quite some time ago, because I'd had absolutely no luck printing my own stuff on my Elegoo Mars 2 Pro: the chess piece came out fine, then all subsequent prints failed. I'd used the metal scraper to get the chess piece off, which scratched the build plate, so I sanded it flat. The parts I tried printing were alternate landing gear for the FP Outland shuttle, and they all either ended up as blobs on the FEP film, or looking like transporter accidents. Discouraged, I took a break from 3D printing, but it went on too long...

Fast forward, and I was designing the glass parts for the old Revell 1/32 '56 Cadillac Eldorado, for Atlantis Models. I'd done work for them before I got a 3D printer, with a long design cycle because they had to get parts 3D printed and mailed to me for test fits. Well, dammit, now I was going print my own or die trying!

One thing I did was to buy extra tanks (I'd need them anyway) and some PTFE spray. My next attempt would be on fresh FEP film, with non-stick coating. I also got microfiber cloths, shop towels, and a space heater for my workshop, because it gets really cold in there, and UV resin reportedly doesn't work well below 20C.

Normally car model windshields are about 1/32"(~0.75mm) thick, so I designed it that way. Lo and behold, my very first print came out okay... or so I thought. Actually, it was distorted, but I didn't notice at the time. A test fit showed me how much adjustment was needed, lather rinse repeat. After a few iterations, I realized the prints were distorted, and that I'd been chasing my tail in a circle.

Doubling the thickness eliminated the distortion as near as I could measure, and after more lather rinse repeat I had a perfectly fitting part, and the kit will be out this summer. BTW, it comes with two pretty nice figures, evidently parked on Lovers' Lane.

Having successfully made it up the foothills of the learning curve, I was ready to slay the dragon who sits on top of a pile of mixed metaphors keeping two hobbits from their richly deserved success at 3D printing! With clear thinking like that, success was assured with minimal effort.

My next attempts were not too discouraging. The Outland shuttle parts printed out with some features perfect, others a little warped, and some long tubular parts failing utterly. I reoriented them and tried again. They were tiny, so I used fine supports. Soon I was getting good parts that let me test out design ideas (they have working articulation) until at last the reluctant dragon was forced to crown the hobbits with laurels. Three cheers and a tiger for me!

Now that I could do no wrong, I proceeded to design parts for Exeter's saucer from This Island Earth. Printing them out would be child's play!

Not quite. As you can see at the above link (or here: https://drive.google.com/file/d/1yVS0On ... sp=sharing and here https://drive.google.com/file/d/1kHCAY_ ... sp=sharing), the saucer rim parts came out distorted. I'd made them thick enough, but obviously the fine supports I'd used for tiny parts were insufficient. I'd also oriented them to hang vertically on the build plate, which seemed logical but might be a problem, because they didn't just pull away from the supports (distorting them in the Z direction), they warped sideways (in the X direction). The sections of the saucer rim are supposed to be 90° wedges, but none of them is quite 90°, even the ones that didn't pull away from the supports. I tried assembling them to get an idea of the distortion, and meanwhile printed the bottom bulge of the saucer, this time with medium supports, and oriented flat, so it would print from the edges down and inward toward the floor.

This second attempt came out better (https://drive.google.com/file/d/1jzj2Bi ... sp=sharing), but I notice some Z direction distortion near where the flat bottom started printing, so it's got a groove all the way around. Also, the smooth curve is represented with visible facets. The big round hole in the bottom is not so much a circle as a 30-sided polygon, and facets are visible over the whole of the curved surface. Sanding will take them out, but if sanding is necessary, it would be good if Chitubox has some way of rounding up what gets printed, so there's a little excess material to sand away.

Speaking of Chitubox, that could use a little more explanation. One thing I found out is it's really important to detect islands, and support them. Unfortunately, they're hard to spot on the screen, even though the slider will stop on them, because they are usually tiny. I try to orient parts to prevent islands. Also, are there settings to control 3D navigation? Left click lets you track, but glacially slow, while right click lets you orbit, but so fast it's disorienting. At least they got the middle wheel right for the zoom.

I'd heard some awful things about UV resin, but compared to polyurethane resin, it's pretty benign. I've gotten both on my hands now, and the UV resin washes off with alcohol, whereas if Deadpool got polyurethane on his hand, especially that spray foam, I'd advise him to chop it off and grow a new one. The only real problem I see along these lines is UV resin gets everywhere, and wearing gloves doesn't prevent that at all. UV resin is supposed to have an awful odor, too, but compared to almost everything else in my workshop, it's practically odorless.

Okay, so back to the beginning, what best practices should I be following?

[TazMan2000]

Temperature plays a huge part in 3D printing as well as the height of the build plate. Try some calibration prints at different layer heights to see if the steppers and screws are working ok.

TazMan2000

[Bellerophon]

Temperature plays a huge part in 3D printing as well as the height of the build plate. Try some calibration prints at different layer heights to see if the steppers and screws are working ok.

The calibration test print is a good suggestion. Thanks, Tazman!

It didn't occur to me that there are test stl files you can download, but a quick search turned some up, so I will do some calibration tests. I expect the machine is perfect, because it still has really low mileage, and now I have temperature under control. I'm pretty sure my slicing software settings are the ones recommended for the resin I'm using. But lots of things can be wrong, like orientation and supports. There is certainly an "area rule" for resin printing, that it doesn't like sudden increases in area.

Meanwhile I tried fixing the orientation of the saucer rim parts. Instead of vertical I did a print at 30 degrees from horizontal, and distortion was much less, but not zero. Also cleanup was a bitch with a forest of supports on the bottom of the saucer. I cut up the saucer differently so all the supports can be on an internal face. (Also Exeter's ship might end up as an injection molded kit - fingers crossed!)