Formlabs Website Store Support

Tough 1500 shelf life and excessively gloopy viscosity

I’ve been using tough 1500 resin with a form 2. (I have only ever bought one bottle of it) The resin is about 18 months old now. I’ve been printing small pieces occasionally with it, as I’ve been developing a design that will be injection molded “in my spare time” ie very slowly. I have left the resin in the machine in the lt tank between prints (I know reading the documentation I see I shouldn’t have done that … but how would I decant it from an LT tray to pour back in later between prints?!)

I’ve had problems of prints failing, and as the first step just cleaned all the optics which were dusty and “foggy”.

I tried a print and again got a fail. I noticed that the resin is very viscous - to the extent when the tank wiper goes back and forth the resin is very very slow to flow in and cover the bottom of the tank after the wipe. (I would doubt it would do so between layers when printing). I don’t remember the resin looking this viscous before.

The machine in kept away from daylight - and in a largely dim room (a spare bedroom!).

When the resin ages (by oxidation? Outgassing?) does it become more viscous - to the point prints will necessarily fail and indeed it needs to be thrown away?

If so is there any work round, eg adding some diluent to make it runnier?

Should I simply scrap what’s in the tank, and try letting the machine fill up from the remains of what’s in the resin bottle ? Ie if the thickening is due to outgassing over 18 months, is the resin likely to have aged in the tank but won’t in the bottle ?

The formlabs data says it has a 24 month shelf life … so it feels like the resin should have life in it.

As I say - the machine is kept away from sunlight, and hasn’t been overly hot (I’m in the uk), so I can’t believe the resin has started curing in the LT tray …

Any thoughts ?

Jonny, I am very interested in your comments, I don’t have any answer, because I am about to start on my first cartridge of Tough 1500
Do you use a different tank for each material?
All the Best Chris in the UK as well.

Have you tried removing the resin cartridge, closing the vent, putting that stupid orange plastic thing over the bite valve, and then shaking the cartridge violently?

The resin has different density materials mixed in. If it sits in the cartridge for a long time with no agitation, eventually the denser stuff settles out.

1 Like

Hi Randy !


I did briefly - and shaking it I couldn’t hear any slopping at all it was so like treacle so I gave up within 25 seconds or so. Perhaps I should go back and give it another go as thinking about what happens with paints that settle out you have to work hard to mix them up . I’ve just thought I wonder if I do something like put it in a salad spinner to start - to use centirugalmforcea to get the materials to “sort” by density - then turn it round and do the same again to force some mixing …

Any suggestions how to mix up a bottle that doesn’t want to get mixed ? (I don’t think I’ve ever mixed it since new, so I’m really kicking myself now !)

Hi there !

Not yet ! (As In I’m not using different materials) I bought the machine explicitly to prototype a component I have which is complex, small and to be injection molded. It has a living hinge and some catch features,
So I really wanted a polypropylene simulant - so my buying the form 2 was driven by that desire, as I couldn’t find any resin for any other printer which could do this job.

I have FDm as well - and most of what I’m doing is fdm to allow me access to “production” technical engineering materials (Eg polycarbonate), as I’m trying to bring a product to market with initially low volume that will be fdm and injection molded .

I do now have some standard resin however so I can print out the optical test pieces - so I’m about to have two materials on hand ! Lol - though other than for the test prices I have no sue for the standard resin material …

Well! To my huge surprise - I think I’m onto something.

I should have said in the original post - that all my prints have failed totally for months with tough 1500, leading me to not knowing what to do. Formlabs support have been superb and helped me by sending me some grey v4 resin, pdfs explaining how to clean the optics,
And getting me to do an optical test print - which the machine passed with flying colours. At that point they concluded the problem was with my resin or tank - and should start with replacing both. I’m loathe to as my failed prints started about 12 months after buying the tough 1500 and I’ve hardly used any of it - so it’s use has been flippin expensive if I were to throw 90% of it away.

So - I figured perhaps it’s the viscosity that’s screwing stuff up - hence starting this thread, and albeit no one has suggested a work round, at this point I felt I have nothing to lose. It either works - or I’ve just scrapped resin that I needed to scrap anyway.

I haven’t read any convincing reasons why resin “goes off” in a non reversible way- when it ages, “partially curing” doesn’t feel right to me assuming it hasn’t been cooked nor illuminated along the way. I wonders if outgassing changing viscosity may (at least sometimes) be the issue - esp given my tough 1500 had gone like the thickest of treacles.

I diluted my tray of tough 1500 progressively with virgin dmp - the solvent I use for cleaning parts,a little at a time and using the wiper to mix it up, till it’s viscosity matched (by eye! ) that of the v4 grey resin I have just successfully printed the optical test print with. To check the viscosity - with my v4 and tough trays next to each other, I’d use the wiper to wipe across the tray - and see how long it took the resin to flow back and cover the clearing, and worked on the tough 1500 till it was about the same as for the v4 (I have no fresh tough 1500 to compare with what it would be like for a fresh purchase), reasoning that the viscosity of my grey v4 is fine given it’s just printed perfect optic test pieces …

After thinning the tough 1500, my form 2 went on to print my model successfully !!! (Albeit confusingly i had set the model up to print twice on the same build -
With the model duplicated on the build plate - same orientation same supports etc. Only one completed perfectly and nothing to see of the the other - but still 50% success I’ll go with !)

The successful print shows no raft lifting from the build platform at all which was a symptom I was seeing on prints when they started failing frequently - before they failed 100% of the time with nothing on the build plate .

I suspect the viscocity going up was increasing the peel forces beyond where the bond to the build plate could survive them - and when on the cusp of acceptable was non the less nearly peeling the rafts off …

I think dmp is a good diluent as resin is extremely soluable in it, it is not very volatile (unlike ipa) and I don’t know but cross fingers won’t degrade the tank … being low in cal tilting seems important so the viscosity doesn’t quickly thicken up again

I haven’t yet washed and cured the print - but it’s obvious hanging from the build platform post print - it printed well - all the detail is there.

Will try and post some pictures when I get a chance to. A crushing work schedule is keeping me away from the form 2 which is not where I have time to visit currently …