A bit of resin alchemy


#6

Thanks @JoshK. I could, but undercuts are a bitch. I was just sitting here pondering, and I’m just about ready to try a 33/33/33 Clear/Tough/Flexible mix and just print the part and use it directly. What do you think about that? I’m using Black profile to print ‘Tuff’, any ideas about what flexible in the mix would want for laser profile?


#7

I never got my hands on tough or flexible, so I’m not sure what the mix would do. As far as laser profile, comparing the estimated print times actually reveals a lot about the power needed to cure it. It seems they use a similar or same brightness, but change the travel speed. It might give you a starting point at least.


#8

I dumped the Tuffer mix out of the heated tank and weighed it. Then I weighed in half as much more of flexible to that, stirred it for 5 minutes, and put it back in the tank. Voila! :new:Tufflex-33. I pushed my finished boot to that material @100um/Black/98-105F and wow! I do not need to make a mold now - this will function well.

I used lots of .4mm points, maybe too many actually, and it printed the 0.5mm wall perfectly everywhere. Nice sharp edges and smooth layering. All I had to do after cleanup and two hours in the lightbox was grab the support matrix and rip it off the model in literally one go. It was like velcro meets bubble wrap if that makes any sense… Minimal sanding with an emery board removed the sightly harder bumpies very quickly. It’s practically as good as a cast urethane material, like say a Simpact 60A, but without making the mold! It feels quite a bit stronger and tear resistant than Flexible. I can’t imagine trying to print 0.5mm walls with Flexible.
Plus, the Flexible profile enforces ridiculous point sizes that destroy whatever you’ve printed anyway. If you need anything like this boot that needs to flex repeatedly, not tear when bent over itself, and be very thin, this might be a good starting point in your own experiments.


#9

Awesome! So the final mix is about 50% Flexible, 25% Tough, and 25% Clear printed at 100°F using the printer’s black setting?


#10

Not quite. My description was a bit confusing. I had 125g of Clear/Tough left in the tank @ 50% each. I added half of that weight (62.5g) in flexible, for a total amount of 187.5g. Or, a 33/33/33 percentage mix of each component.


#11

Here’s a quick video of how this Tufflex-33 resin mix looks and behves in action:


Retro Form 1+ Guide
#12

Wow, that looks amazing. If that stands the test of time everyone is going to be mixing that! Keep us posted on any property changes and how long they took.


#13

Great work, I especially like the Tufflex-33 name. =] Recovery is a bit slow but overall it looks great.

Getting that thin of a wall to print well is a tall enough task, glad it also has the performance you were hoping for.


#14

It’s funny. It never dawned on me you could mix Form resins with different properties to get new properties. Thanks for sharing and opening my eyes to possibilities. The boot looks great in the video.


#15

It is. The result is more plastic-like than rubbery. It bends well, but it has very little elongation. It feels like it has pretty good tensile strength, but I need this part, so don’t want to find out :wink:


#16

It’s not just mixing resins, there’s colorants out there as well that I have added to clear to get deep colors (albeit only using the resin in it’s liquid state for surfacing some stuff). I have not tried the colorants in the tank yet, as I was afraid they may tint the PDMS too. Before I resurface this tank I’ll try that. Hopefully it will not affect the PDMS, and we can have any color we want just by using the primary color colorants (+ black) at this link. Then, I can make the boot black like I want it to be.


#17

@Formlabs This kind of thing is why we need more knobs and gauges. That, and a bit more transparency on the differences between the hard-coded material profiles in Preform. An expert mode that parameterized everything would seriously be awesome, and would empower the community to get stuff done. This will only help you in the longrun.

-C


Mixing resin
#18

+1

Just make us sign a disclaimer and agreement that we won’t come crying to you when we muck everything up. Your printers/software are brilliantly easy to use, but we want to tinker!

Unfortunately there isn’t much value added in spending the time adding these features to the interface. Form2 is launching with open resin mode so this concern is at least on the radar.


#19

Update: after a couple of days, the Tufflex-33 has gotten quite stiff. Too stiff really for it’s intended purpose. Recovery was slow, and now it’s r e a l l y s l o w. I’m going to make up and test a batch of Tufflex-50 (50% Tuff, and 50% Flexible) and see how that goes. I may end up having to mold this part after all…


#20

Thanks for the update. So good for prototyping, but not stable. When something is printed in Formlabs Flexible, do you notice a hardening within a few days too?


#21

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…


#22

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. =]


#23

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?


#24

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.


#25

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.