90-odd pecent success. How accurate is a resin 3D print?

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lee webster

Well-Known Member
Oct 4, 2019
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Cornwall UK
I looked very carefully at my printer settings and changed them. My last few prints were using the default settings. When the build plate is lowered into the resin vat and then raised, it can cause a lot of suction. I slowed the raising of the plate between layers to reduce the effect of the suction. I also increased the time between layers so that the UV light would have more time to set the layer of resin. I set it to print and walked away. 2 hours later I had a look at the progress and there was only 4 minutes left to completion. I could just see part of the build plate and it seemed to have things hanging from it. All 4 parts had printed almost perfectly. I say almost because the surface finish where the supports were was awful. It looked like the skin on a rice pud. The parts were washed and cured and left to sit for a while. Some of the parts had 4.1mm holes for set screws. A 4mm set screw slid in with hardly any play. 2 of the parts had flanges on to locate in a recess in another of the prints. They were a good fit in the CAD programme, but oversize on the prints. I can live with the rough surface, it's on a face that isn't used, the holes are OK, maybe a little snug. But the flange fit is something of a concern. I think I might do away with the flanges and introduce holes for a dowel.
So, how accurate do you think a resin print shoud be?
I have been giving two resin printers a good workout. One is the Anycubic Mono and the other is the Eelego Saturn. Depending on the type of resin you are using you can expect a little shrinkage. With Bigger parts the shrinkage becomes noticeable. The Saturn has a large build plate and I have found it needs a time delay before turning on the light to give the resin a chance to flow out from between the Fep and the build plate. I agree the surface that has supports connected is a bit wonky at times. I am using a casting resin that needs large and numerus supports. The surface that the supports attach to are very bad so I plan ahead and give that surface a little extra thickness to machine away. I have also been using Sirya Tech BUILD resin. Prints very well and is machinable.

All & all I am very pleased with how well the resin printers perform.
I discovered this evening that the surface deformation between the supports is called "sagging". It's nice to know that it wasn't a fault with the printer! I use Prusa slicer to produce a finished STL file that I can import into Photon workshop slicer to create the sliced file for the printer. I also discovered this evening that Pusa slicer will attempt to orientate the part on the build plate to get the best surface finish. I might try just printing on the the parts this way to if it works.
When I started looking for a resin printer I couldn't find a Saturn anywhere. Many printers were out of stock. They all seem to be available now.
I decided on the Anycubic Mono 2G as the resin printer that I wanted but as I dithered and flustered the 4G popped up at a reasonable price. I watched some you tubes on the difference between the two and the general consensus seems to be that it is not much. I am leaning towards the 4G anyway but as you say they are hard to get. The usual vendors are sold out. Gives me time for more dithering.
Your resin can make a huge difference. I had a lot of failed prints with the Anycubic standard resin. Parts that should mate up did not, squares were trapezoids. Only one partially failed print so far with Elegoo standard grey resin and the one thing I've printed with a square pin and socket on two mating parts fit perfectly with just slight filing of the square alignment pin. I'd swag 90% or better fit straight from the printer. The same print with the Anycubic resin wasn't even fixable, lots of warping. The partially failed print was really pushing the luck, a tall complex statue model from an original in a museum. It just hit me right, would look good on the desk, and is a change from model railroad scaled stuff. Painting it may make it OK, lots of odds and ends misshaped or missing on many statues anyhow. Just a missing leg, guess I can call it a tribute to Paul McCartney's last poor spousal choice :) At least it won't cost me 43 million if I trash it. If motivation overcomes inertia I'll split the print to allow better alignment on the bed.

I've been rather disappointed in the amount of freckles and zits left by supports in the resin prints as well, although a model that can work with thin supports and aligned such that the important faces are not supported directly can be quite good. Lychee Slicer allows adjusting the support contact shape and penetration into the print, so you can reduce the issue at the expense of weaker support. Sadly all surfaces matter in some cases.

Slightly off topic, I just received my Creality Ender3 S1 Pro and this is a very nice FDM printer. Naturally not as smooth a surface finish as resin, but very nice, very good print quality by FDM standards at a 0.16 mm layer height. Quite good at 0.2mm. The S1 Pro is a direct extruder able to handle materials up to 300C so carbon fiber filled nylons and such can come to the party.

I've just added the lower cost direct drive extruder and ABL stuff to my Ender3V2, so far so good. Slightly better results with some hard to print stuff, utter failure with some others that always caused problems. Small steps forward, not huge improvements.

Best to all,
I ordered a bottle of Elegoo water washable resin, it should be delivered today. I tried to get some microfibre wipes for the FEP cleaning, and a bottle of IPA. No luck so far, I will try in town in a day or so.
I still use my Ender3 for simple prototype printing, less cleaning up and cheaper.

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