Best resin for static loads?

I have a prototype that needs to support a static load but also withstand vibrations without cracking (standard resins are great at static loads, but can be brittle).

I’ve tried Tough v3 for this and it appears to deform over time. This may be due to improper/incomplete curing (I have a UV cure box, but it’s makeshift: no heater, and no measurements of the UV flux, and my Formlabs cure box won’t arrive until February, apparently). But I also had experience with previous version of Tough and they bent like taffy under static loads as well.

I have Durable available, but I’m dubious that it would deform less than Tough, so I haven’t tried it. What about High Temp? It looks like it might be better at holding its shape better than the standard resins, but I wonder if that same property won’t make it more brittle. Does anyone have experience using High Temp for anything other molds?

If you need a material that can withstand vibration it’s best to print a master or mold and cast the parts in polyurethane resin.

You can get material that will be pretty much as hard as the Formlabs standard resins. Smallish parts are actually fairly easy to cast.

High temp resin cannot withstand much loading. I had parts where we would crimp a metal cup around it. This worked well until the part went on high temperature(140C) and it cracked. This material is reasonably brittle.

The standard material you tested, was this V2 or V3?

Some people have mixed tough with standard resin to improve the characteristics. Maybe this is an option too.

That’s a good point; it may make better sense for me to stop using the printed parts directly in my prototype once I’ve finished iterating on the design, and instead mold them. I don’t have any experience with casting in polyurethane, though it doesn’t seem difficult in principle, my parts are probably not designed with easy moldability in mind.

Ok, good to know. I guess it makes sense that for these resins, the harder they are the more brittle they’ll be.

So far I’ve tested Tough v1 (very bendy) and v3 (much less so, but still deforms under load), and standard grey v2 and white v1 & v2. The grey v2 holds up well enough, but as I say it is prone to catastrophic failure without much warning, which generally leads to a chain reaction and a spectacular shower of plastic. Fun to watch, but time consuming to recover from.

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If you like the properties of V2, save it for your most critical jobs. V3 is worse.

You might consider plating parts. Here are a couple of providers. I haven’t used them yet, but have gotten a referral to them from another Form user:

Any impact-resistant material in the Form 2 is going to creep and deform over time.

“which generally leads to a chain reaction and a spectacular shower of plastic”

I have also stiffened and strengthened parts by printing through-holes and putting metal rods/tubes inside. Completely geometry and loading dependent though.

Repliform is a great option, I have gotten many parts plated by them. SAT is another good vendor but they typically do really thin coatings so I am not sure it would be structural enough for you. From the sound of it, I think your best bet is to plate the most recent version of Tough.

Casting is easy if the parts are designed properly and you have good release, good venting, tooling, etc. Probably not a bad skill to bring in-house but one of the benefits of 3D printing is being able to get crazy geometries that don’t mold well.

I have had good results of mixing black and tough. For Snap-Connectors I use 33% tough with 66% black. The mixture has combined advantages of both resins (accuracy, strong and tough)
That is my general go-to resin mixture. Printed through the black cartridge (with black settings) on the Form2. I always print with the 25µm setting, so I can’t say anything about the other settings.
I currently print about half a cartridge per week (which is alot, at least I think so) and have used this mixture for about a year now.

Slight disadvantages:
-You have to take out 1/3 of the black in a new cartridge and store it in an old cartridge. Use a funnel and a painters filter.
-You must mix it thoroughly. This is easier if the cartridge is not full.
-The color of the print is a dark grey, and not the nice black. And you may get sedimentry lines in the model. I have only mechanical functional parts so this never bothers me. For nice looking prototypes painting is necessary anyway.

I did also try this (mixing) with grey. I had issues (warping, cracks) and will stick with black&tough.

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Awesome, thanks all for the tips.

Sounds like trying polyurethane might be a good first step, along with trying to mix resins for the right properties (though I don’t have any black left so it’d have to be with V3, which I hear is much more brittle, exactly the wrong direction).

The plating would definitely solve my problem, but maybe only after I’ve made more progress on my project since I’m guessing there’s turnaround time and expense.

I can vouch for repliform! They do great work, and the parts are really robust after metal plating.

My rough mental model for the materials…

most brittle, stiff < - - - - - - - - - - - - - - - - - > least brittle, prone to warping
high temp, standard, tough, durable

I would have thought Tough would have been a good bet. It might depend on the geometry, Durable could work and would certainly get you towards a ductile failure mode but for thin parts it is very flexible.

For small parts, moldmaking is a good way to go. You might look at a rubber vulcanization process, we also tried a sacrificial casting process.

I have also heard of customers mixing black and tough to get some ratio that they prefer.

Repliform are great, we use them to plate parts and we’re working on some more resources on this topic.

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I can also vouch for repliform, great work.