A bit of resin alchemy


Flexible doesn’t really harden, but it’s a weird consistency. A stale gummy bear is as close as I can imagine to describe it. I’m assuming that part of what was being photo-reacted was still undercured, and that it continued to cure, getting stiffer. I’m thinking more Flexible, but not 100% Flexible, might be better. We’ll see…


I think that should provide good results. Tough is similar to flexible but resists shearing much better. Would Tufflex-33 still work for your snap-fit assembly or does it recover too slowly even for that?

I don’t post cure my clear parts (not a controlled post cure that is) but they do get brittle over 24 hours. I had been using a part with a press-fit assembly with a machined PC part and within the same day of post processing the press fit works wonderfully, a day later, every single one broke on me. I always assume this was due to post curing via ambient light but there might actually be some property change over time that isn’t cure related. I wish I had a three point bend tester to investigate, I suppose I could fudge my own.

Lastly I wonder how the post cure affects the flexible resin within the mixture. AFAIK a post cure is required on tough but only recommended on flexible to remove the tacky surface feel of the uncured resin (water submersion highly recommended) In my own experiments I accidentally baked a flexible part under a production UV flood until it was yellowed and lost some of its flexibility. This happened surprisingly fast. Though if this is what you were running into with your property changes I would think it would have been stiff immediately after post cure.

Fascinating stuff, keep us updated. =]


No, the Clear/Tough @ 50% each (Tuff) works excellent for that. Clear was great, but as you know, it gets a bit too brittle. For most everything I’m doing, except for rubber parts or course, Tuff has been fantastic so far.

Since Tough and Tuff sound the same, we need a better name for this hybrid mix. Ideas?


I haven’t had the need to make the differentiation in spoken conversation so it doesn’t bother me much… How about DuraVis?

This brainstorming reminds me of plastics compounding companies naming their proprietary resins.


Hi guys

currently printing with 50/50 mix (tuff) but without heater.
I’ve done the mix without measuring by mixing the resins 50/50 directly in the tank.

after hour I will post the results, but for now the model looks with very good detail for 100 microns.



I’d be interested as to how 50:50 Tuff puts up with spray painting it? Especially bending it? And also what is the natural color like? I’d like to see photos! :smile:


The photos are bad but the print is perfect!!!

The surface is with marks because I clean my parts for constructions with painting brush, I don’t care about the appearance of the model in those cases.

The holes are really round, and I can say this is one of the best prints I ever seen on this printer.

100 microns settings for Black resin

I will make some tests tomorrow


Which resin is most durable

Cool, thanks, looking great! Let us know about the tests. Maybe even a video.


Ok, no problem, will make a video tomorrow.

I have 2 broken models due to dust on the mirror so I can show you on them.

The parts really can’t break. They are very strong and in the same time a little bit flexible, but not much. Just perfect.
I don’t see the need of heater! May be will be a little bit better if the resin is heated but I have great results with no heater.

I think this mix is the ultimate material !


Why thank you :slight_smile:

It is very good unheated, but it’s really, actually even better[1] coming out of the heated tank - trust me on that. Once you use the heated resin, you’ll never go back.

[1] more accurate finished parts, less strain on system/part during peel, better for tiny or fine parts/details, smoother finsh.



Yes, I’m pretty sure heated is better.

Will try it this weekend if I have time.

I like that the holes comes really round compared to standard materials.

Chris what You think about 70/30 tough/clear??


It’s good, as is 80/20, and it’s properties change how you’d expect.

I’m trying 50/30/20 of tough/clear/vorex black right now, and the results are ‘interesting’. The color is kinda cool, the properties are good, but it’s still got that vorex stickyness/gumminess if you know what I mean. That, and vorex is pretty stinky…

I’m going to be trying 50/30/20 mixes of both tough/clear/white and tough/clear/black to see how those perform/look.



@ChristopherBarr I’m interested to know how your experiments came out as this thread has gone quiet. Ive recently been playing around with the tough and clear for prototyping thin wall thickness’s of 0.8mm for micro electronics. I was just wondering if you had found an optimal mix of tough/clear for thin walled prototypes?

Tough on its on is just way too flexible. and 50/50 still flex’s a little too much. Any ideas?


What’s best for your application I can’t really know given the amount of requirements data above. The hardest and stiffest when cured seems to be Clear by itself. Have you tried that by itself? If that proves too brittle for other reason not mentioned, then add a small amount of tough to see if that makes it a bit more durable for you. 50/50 worked pretty well for my 1mm wall snapfit part requirements.

I like to think of it as mixing colors. Each material has specific properties that come through in the final mix in proportion to their quantities.

I’m building display-type functional prototypes now, and plan on trying varying mixes of black v2, clear v2 and tough v2. My first mix will be to add in an equal amount of black to some 50/50 I already have, get a baseline, and see how that feels. In this case I want black-ish plastic with mostly the properties I get with 50/50. My gut tells me it will be a bit less durable, a little harder, a slightly translucent dark blue-green gray in thin sections, but it will have a nice surface and look kinda cool with just a clear-coat sprayed on later.

My advice is to try to understand the essence of each resin on it’s own, do thought experiments about how they’ll behave when combined, then experiment and see if your ideas are correct. I think after a while you’ll be able to just know how a mix will behave before you even mix it.


Thanks for the advice! In the time since my post this morning ive managed to try a mix of 80/20, clear/tough combination which has turned out much better, using the 50 micron print on black v2 settings. I’ve yet to try a three resin mix as most of my prints are for functional prototyping rather than aesthetics. But it would definitely be interesting to try the black mix for display prototypes where colour is more important. My next steps are to work out the optimal cure settings.

According to formlabs its best to post cure tough at 45 Celsius for 30 mins give or take but i found post curing the clear just turns the parts yellowy. So im going to test 4 of the same prints at different post cure durations. Have you had any experience with the post cure times for the 50/50 mix or even 80/20?

i wish formlabs would allow its users a more advanced UI with defined parameters, it would make debugging failed prints so much easier!


I’ve never been all that precise about post-cure. If it’s sunny out, I’ll often just stick parts outside for a while. Otherwise I put them in my curing box for a while until they feel ‘done’.

I’d definitely be interested in your findings on these four samples. Maybe create a spreadsheet or just a simple table of your results and post here?



I went ahead and ordered the dry heat uv sterilzer on Ebay and it should arrive next week. It has a max setting of 80C so it will be able to reach the recommended cure settings as advised by Formlabs. It has a T5 florescent uv tube, don’t know the nm but I have a few here I can try to see how they work with the heat. I am planning on having some printed parts plated by Repliform and they recommend that the parts be fully cured before they plate them and that I not use any UV clear coat or oil on them for best results. I will hold off sending the parts to them to be plated until after I have heat and UV cured them in the new box when it comes. For $99 it is a bargain if it works as advertised.


I really like working with tuff, it is not as brittle as regular resin! I do have one problem, it is extremely diffucult to remove from the build plate, have you guys experienced the same?


Try lifting your build platform in Printers->Fine Tuning->Z offset by 0.2mm, and see how that helps. Not enough, go up 0.1mm at a time until parts come off easy enough, but stay put during printing.


I have a couple prototypes out in the field now for about 9 months that haven’t snapped that were done in the clear resin. I had no issues with tolerances but I also use YM for cleaning and NO IPA.
I found IPA distorts the parts and drastically weakens it. Most of my parts get tossed into a vulcanizer under 25 tons @ 310F for an hour for mold making.

I was interested in the tough but the resolution is only good down to 50 microns and the resin seemed too soft for my application.

If your snap fits don’t have an extreme deflection the clear should do the trick, think it is good for about 30% max.

If you need to make a gasket can you print a mold for it and put some silicone into it?