Playing with Printers – Resin Exposure Time

So, one project I’ve been working on for the last month is trying to tune my printer settings. There is something of a balancing act in the resin printers which revolves around the exposure time. Basically the length of time that each layer is displayed on the LCD screen to cure the resin.

This trade-off is mainly between detail and success rate. Higher exposure times will “bleed over” the edges and obscure finer details. It also lends more strength to the model and its supports. Too little exposure and the supports will fail, leaving you with an irritatingly difficult to clean “puddle” on the bottom or missing limbs. Just depends on how far off you were and what size the supports were.

One of the accepted ways to narrow this down is to print these XPS calibration squares with different settings and see what you end up with. Ideally you get a very sharp point on the center infinity section and the positive bars at the bottom should look like they would slide into the negative space below them.

In this case, you can see that 5 seconds looks about right since the 6s is too large and 4s is missing a lot of the finer bits. Something I did note, though, was that all but the 6.5s were missing at least one of the positive dots on the left side. Had I noticed this when doing the squares, perhaps I would not have experienced as much trouble.

Before this, I had been printing at 8s per layer, which isn’t absurd, but it was overkill for most prints, and having the display on longer than it needs to be degrades it rather quickly. As it is, this one already has some dim spots and flickering.

The “Failed Print” box full of mostly supports.

Having decided I would try a proper print at the 4.5s mark so I loaded up a print plate full of bandits and got mostly supports. Only three models out of eight lived to see daylight. I wasn’t really surprised. The rather severe damage to the 4s calibration square suggest this would be an issue, so I did the only reasonable thing and kept repeating the job adding a half second at a time.

The print job as a whole takes about 2-3 hours print time, plus whatever setup and cleanup is required. This typically meant I could get in about one set per day, starting the print either before I left for work or right before going to bed.

In the full-size images you can see some of the places where bits didn’t quite print correctly. The female bandit and the one with mace were particularly troublesome. I probably could add some supports of my own to the trouble areas, but wanted to keep things consistent just for testing purposes. I will probably consider 6s my standard for the moment. At least for this printer and this resin.

There are some flaws that stand out in this test as well. I didn’t think to record the environmental conditions for these prints. While it is being done in a somewhat heated space, it was still well below the recommended temperature range at times. Maybe I’ll do a repeat in the future, but honestly, I don’t need these figures, I just needed something with fairly fine supports to test the settings and this set had two different kinds of supports.

My next set of test are going to involve post-processing. There is a noticeable difference in surface finish from batch to batch and I haven’t quite nailed down why, especially since I follow the same general steps every time. Off the printer into the ultrasonic cleaner for around 10 minutes, then rinse, lay on towel to dry, and a pass in the curing box. In fact, the yellowish tint to the 6s set was because they spent more time in the cure box than the other sets.

Still, that’s a problem for another day.

I haven’t yet decided what to do with the failed prints. Outside of the one half-woman most of these are salvageable, at least for personal use. These models were sculpted by TytanTroll, so if you want to make them yourself feel free to check out his MyMiniFactory page or his Patreon. I’m technically licensed to sell prints of his models as well, if that’s something you’re interested in.

Y’all take care. I’m gonna go stare at the wall for a little bit myself.

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