I have various prints in Clear V5 off of my 4L. They are various sizes. Some of them have hollowing, with pretty thick walls, all with a hole per-pocket for cupping reasons.
After the print is done I wash and cure. Some of them have drained pretty good. Some I have flushed with 99% isopropyl and let drain.
Eventually these were sealed up. I would glue pegs in to the holes or fill them with typical 3M spot putty.
Recently I came across something I never knew about which is that over time left over resin can expand inside the hollows and āexplodeā the model.
How much should I worry about this?
Should I go through on these and do very small drills in the areas I filled in?
Iām not sure how much resin/iso is inside some of the hollow pockets. Iām guessing the worst is probably not too too much considering how things printed + oozing out. But I imagine there is definitely some inside on some of these. Namely the ones I didnāt flush out.
Thanks
P.S. Hollowing has been rough in general. I filled a lot of these drain/relief holes in because items would just keep oozing, even if just a little bit, for a long time. Also so far I have only been doing 1 hole per pocket.
How thick are the walls? Resin typically is not meant to be thick in models, as it closely resembles thermoplastics that are prone to warping when walls are too thick. The only time Iāve heard of models āexplodingā is when there is uncured resin trapped inside and the off-gassing creates pressure or because the resin chemistry weakens over time (a few years).
Without any pictures to see, kinda hard to envision based on your words. Understandable if your models/prints are proprietary and you canāt share them here, but it would help to see what youāre referring to
This is a ~3 inch tall figurine character. One image shows the helmet and should probably about 3mm thick. And then the legs I hollowed out from ankle up to the pelvis area and should be about 3mm thick i think. I believe Default hollowing in Preform is 1mm.
Printed in Clear V5
Also Kemolagger can you please expound more on āā¦ the resin chemistry weakens over time (a few years)ā. any details there or perhaps numbers? How much does it change over how long? For what resins? I donāt know if like this figurine in 3 years crumbles in my fingers or if in 8 years I drop it and it breaks a bit easier than it would have after 1 year. I understand if its unpainted sitting in the sun is different than if its sitting in a drawer coated in paint or something. Iām just trying to get a better understanding of this phenomenon. Thanks!
Iām speaking generally from consumer grade resins, and canāt really comment if Formlab resins will break down over time. As I understand it (and Iām by no means an expert, just a curious young Ladd with an eye for printing stuff in his basement), nearly all chemical bonds break down over time - hours, days, weeks, months, years, millennia. Most petroleum based plastics will break down over time. Plastics will weaken, silicones will start oozing (had many Oakley sunglasses that did this). The same happens with resins, the chemical handshakes start to lose grip over time. UV exposure expedites this weakening. Now, I have many consumer grade ABS-like resin prints that were printed 4 years ago and are still going strong - chemistry really matters here and the quality of the engineering behind it. Thatās all Iāll really say about it, and hope that more intelligent and esteemed folks chime in (from formlabs hopefully). You always want to make sure that any liquid resin is mechanically broken down and removed from any print (using IPA) prior to curing and especially after. Even though clear resin is, well clear, that doesnāt mean that photons have a direct path to hit the uncured resin in a curing chamber.
Sorry to not answer your original question, but as long as there is no liquid resin remaining and you can verify that the interior is in fact dry of both resin and IPA - you shouldnāt worry about explody prints down the road. Most of if not all of those stories Iāve seen on reddit of a print crumbling and oozing months or years later are because the model was not āholedā with weeping holes and resin was trapped inside.
When dealing with hollow parts I off course add drainage holes in the model for draining and to prevent cupping.
If the model allows it, I add drainage on the top and bottom, so I can flush it really thorough with fresh IPA.
Covering up the drainage holes is no problem, but I would advise to always keep a small hole in a hollow part, I usually keep/drill a 1 - 0.6mm hole, because Iāve seen thin walled designs collapse and or expand during temperature change. This will also allow your model to vent leftover resin/IPA fumes too.
As far as the resin exploding, when resin cures it contracts, so it isnāt going to inherently cause an the part to explode outwards. That said what can happen is leftover uncured resin can definitely soften resin parts, which makes them a lot more prone to getting floppy. More familiar with this when parts have walls on the order of 1 mm and less, but depending on the resin and how much material is in there I could see it happening to a 3 mm wall too. The other big thing to keep in mind is if you seal it up, you now have a bunch of air captured on the inside, if that air gets warmer than it was originally, it can definitely cause the part to explode.
Iāll echo Mr_Solissa, add drain holes and flush it out with IPA as thoroughly as you can. If you can, let it dry for 30 minutes or more before you UV cure it to let it dry.
Aging is a somewhat different topic, but itās closer to your later comment of if you have a part for a year it is going to be more prone to breaking when you drop it. If youāve painted it and are storing it inside, realistically the part will maintain reasonably good properties for a decade or more. If you leave an unpainted part outside, youāll see properties drop much faster (you can look at our Tough 1500 V2 TDS and see the accelerated aging graph that we did). My general experience has been that parts that you keep indoors and arenāt heavily loading will not have a noticeable change in properties for years, but your mileage may vary.
Itās almost certainly not the resin causing the āexplosionsā but the fact the holes are sealed. Resin breaking down is not the issue. The resin is fairly stable, low VOC, and the bottles donāt puff up on the shelf. The main culprit is likely off-gassing IPA from leftover liquid resin, and from the small amount trapped in the cured resin. One ml of IPA turns into 0.3 liters of vapor, so if you donāt leave a hole, you are asking for trouble. If you clean them perfectly, and let them dry thoroughly, I would still leave a hole. Air changes volume by about .2% per degree C. Not much, but a print sitting in the sun or taken out into the cold will absolutely warp a bit as a result.
