I have had my LT take for for a few months now and I am very unimpressed. I have only done 9 prints ( 2 of which were failures, but is hard to tell if there are due to the LT tank or the v4 black resin, which is also not great) so far and the surface is already scratched beyond use. I admit some of this is due to me using the metal scraper, I wasn’t aware I wasn’t to use it. Others have pointed out that there is a sticker that says otherwise but I didn’t see it. But regardless, it also has long scratches due to just the wiper movement (see images). There are also divots and distortions in the surface that appeared on the after the first failed print. I’m guessing it was caused by a piece of cured resin was caught under the wiper. Has anyone else noticed these problems as well?
Are you seeing print failures or a drop in quality? I have some tanks that have developed these scratches as well but are still generating good prints.
The print quality seems to be ok for the models have have printed out fine, but I have had some failures. I am using the v4 black resin which I haven’t used before as well, so it is difficult to diagnose if the models failed due to the tank or the resin. I am in the mind that it is the resin as other have expressed similar problems with the v4 batch.
My concern is with the scratches is that I have only done 9 prints and that is the already amount of damage done to the surface. The chances of the LT tanks last 10x longer than the standard seems very unlikely to me. The fact that just the wiper itself is damaging the surface is a big issue. It may be because the black resin has some heavier pigment that gets dragged along with the wiper that causes the scratches, but I feel that Formlabs would have tested for that and advised against using the black resin with the LT tanks if that was the case.
The scratches are not such a big deal. There is a big difference between a scratch or a smudge on the mirror or optical glass (which is relatively far away from the target area) and a scratch that is pretty much in contact with the target area.
If you are not seeing a degrade in print quality don’t worry about it. This is not PDMS and while it is fragile (be VERY careful removing failed prints) the scratches don’t seem to affect print quality appreciably (for me at least).
Is your build plate gouged at all? I’ve gotten after students for not carefully removing the parts from the build plate.
Also, how does the wiper’s edge look? Couldn’t see it in the pictures, but that’s another place to look.
Luckily, I noticed the slight gouges before the build plate was reused. The gouging raised aluminum from the build plate ~0.15 mm, so I assume that’s maybe enough to interact with the top surface of the tanks? (First few layers only, of course.)
So far my only gripe with my LT tank is that I have to re-seat the thing before each print because the printer thinks it’s missing.
I never use the included metal scraper on any tank and have some plastic putty knives for that purpose.
I’d like to know why Formlabs doesn’t use glass for the tank bottom other than the potential breakage issue. Maybe Gorilla Glass is the answer.
I’m gonna guess your failures are more due to the black V4 resin. I have not had much success with it even when using a brand new standard tank. I swear the wiper arms sole purpose is to wear our tanks faster. Printing without the wiper in open mode seems to work just fine.
They dont use glass cause its more expensive especially tempered glass. Regardless you still need a pdms or similar rubber layer between the build plate and tank bottom as far as I know. The inherent issue isnt the tank bottom its the soft rubber layer. I think a better design would be a low cost replaceable rubber layer. Sure that would mean less money for them but it would be cheaper and less wasteful for us.
i really don’t understand why anyone would take a metal scraper to ANY of the tanks.
would you do that to a teflon skillet?
For $1.99 at any grocery store you can buy a silicone rubber spatula that will do the job without cutting or scoring the tank surface
My build plate is fine, only a few very minor scratches. The wiper is also fine, its the brand new one that came with the LT tank.
Yeah, the v4 black is not great. Both of the failures I have had were from the supports snapping off at the base, which has not been an issue with any of the other resins of the 100+ prints I have done. The wiper arms are fine of the standard tanks, but they scratch the hell out of the surface on the LT tanks.
OK, for giggles I did a materials only cost comparison using raw materials readily available from McMaster-Carr www.mcmaster.com and they are far from the cheapest industrial supply house in the USA; but they always have what I need.
Anyway, I don’t think the cost of the glass versus PDMS (silicone) coated acrylic or whatever is the main substrate of the window. Mind you I made assumptions about materials used and tank window construction. I did not factor in fabrication costs as they are unknown to anyone outside of Formlabs.
0.005" clear silicone sheet: 12" x 12" = $92.59
0.125" Clear UV resistant acrylic: 12" x 12" = $6.50
$24.77 per 6" x 6" window made of both materials sandwiched together.
0.043" Gorilla Glass: 12" x 12" = $103.28; $25.82 per 6" x 6" window.
0.125" borosilicate glass: 12" x 12" = $46.48; $11.62 per 6" x 6" window.
For the black resins I have found the metal scraper to be essential. The pigment they uses settle on the botton in a matter of days into a thick sludge. I have tried rubber scrapers but they dont do the job. I never had any issues with gouging or scraping on the stand tanks, the LT ones though… not so much.
Suspiciously Formlabs tells you to use the included sharp edged steel putty knife to inspect your tank surface and remove any debris. I kid you not their are little clips of them doing it. I have a soft plastic vinyl application squeegee I use.
I have recoated the PDMS on my Moai SLA. Its far cheaper than buying another tank. I guarantee you those tanks dont cost more than 20 a piece to make. Yeah they def dont pay $6.50 a square foot for their acrylic either.
There is no sandwiching at all. Its just a 2 part resin that gets poured into the tank by a certain weight that then cures to form the rubber layer. The amount required to re-coat one Moai tank cost me roughly 15 or so and I’m sure it costs far less for a company buying the rubber resin in bulk.
A plastic squeegee used for auto body filler is a better idea than a rubber spatula. Its hard enough to remove debris whilst being pliable enough not to scratch the rubber as long as you’re not going crazy.
I rounded the edges of my Formlabs metal scraper on my bench grinder in the event I need to use it.
The plastic putty knives I have on hand are 1", 2" or 3", and 4" and I got them for less than $5 on Cramazon. I’ve seen them in the hardware stores for similar prices.
Do you have a source for the PDMS you are using?
Here is the forum post I followed. https://forum.peopoly.net/t/how-to-restore-your-vat/195/24
Here is the PDMS I ordered. http://www.mlsolar.com/cell-guard-solar-cell-encapsulation-for-making-solar-panels/
It would be a good practice to clean the tank you wish to recoat then carefully remove the old rubber layer and weigh it. Then use that weight as a guide for how much to mix. Also the stuff cures faster when heated. I used a level to make sure my tank was level before pouring in the new coating.