Impact resistance, flexibility, heat resistance of cured parts?

Has anyone tried to see how well the cured resin can withstand impact from something like a hammer, or how flexible and heat resistant it is? I’ve seen the functional parts and planetary gear videos, but neither shows impact, flex, or heat resistance.

I plan on printing some parts for toys that deal with spring pressure and sudden impacts (such as spring-loaded dart guns), parts for RC cars that could benefit from some amount of flex, and parts where heat-generating electronics may be involved, such as LEDs. I’d like to know how well the cured parts stand up to different situations so I know if the parts I produce can be used as-is, and so I can start planning accordingly and inform potential customers what they might be able to expect. Of course, the design of the part can be as much of a factor as the properties of the material, and I expect to go through revisions to the models, but sometimes even the best design can’t make up for the material its made of.

It’d also be great if someone could destroy some unneeded and/or failed parts on video… for science! :smiley: Kinda like this:

So from my experience, once you get a certain thickness (around 1-2 square mm), the resin starts to be pretty strong and very hard to break. Smaller details are a bit more brittle and may have to be handle with more care. A model crash test hack and slash fest video sounds like a great idea!

If no one does this by the time I get my printer, maybe I’ll test this myself and record it. :wink:

That would be great, Tj, if you could show how easy it is for the cured resin to be cut.

I, too, would like to know specifically about heat resistance.  I work at a plant that uses vacuum forming for packaging and would like to make vac forms with the form1, but it needs to resist 180f for hours at a time.



Testing vids would be great TJ!, and Reid I’d also be interested in seeing that vac forming with Form1 prints, that’d be cool to use a print to make a custom formed display cover for another print!!!

Expanding the list of properties a bit more, does anyone have any information on the electrical conductivity of the material (given the basic substrate, I assume it is essentially an insulator)?  Has anyone seen any hardness numbers for the material?


We currently have a couple of hundred Aluminum forms for the standard stuff, but we do get special orders, and can’t afford to “one-off” an aly form.  This would be a great application.  We just tried it with a form printed off the Dimension 1200es that the local CC has, but the surface is not all that smooth.


If I provided someone with an STL file, would anyone be willing to print it for me, send it back & I’ll test the heat resistance in our Vac-u-form?  Be happy to pay for the piece (about 4x1.5x0.375 in or roughly 1 ci) and shipping!



Hey everyone,

I’ve been printing a number of objects over the past few days, and (as expected) I’m slowly amassing a pile of failed prints. I’ll be doing a write-up about my findings sometime this week, and I’ll see about doing some tests with those failed parts.

One of the test objects I printed was created specifically to stress several aspects of the material and printer, and while the test failed, it provided me with a huge wealth of information.

I’ll see if I can do some flex, impact, and heat resistance tests, though I won’t be able to report anything super-scientific since I don’t have those kinds of instruments lol.

Initial findings on flexibility: The flexibility of the parts largely depends on the thickness (of course), and length of the part flexing. It also depends on how well the part was cured. I’ve found that every part I’ve printed so far has come out only partially cured, and needed to be set out in the sun to fully cure afterward. After several hours in the sun, the parts were usually fairly rigid, with parts with more density and thickness being far more rigid than the thinner parts.

I haven’t yet been able to do any impact or heat tests. Again, I’ll be doing a more substantial write-up later. Currently, my Form-ing computer is offline because of a power supply manufacturing defect. I’ll see if my other computers can handle more prints soon. :)

TJ, I hope your getting successful prints also, and some videos would be awesome!

TJ -

Thanks for the update.  With the heat test, any chance you can get it in a slow oven (about 200*f) for about 2 hours?  This would give me some good data to go to management with.


Can’t wait to hear more, thanks Tj! pics pics pics!

I have no scientific way of measuring any of the physical properties of the resin, but I found that after print the resin is not fully cured and rather soft.

Once you put the object in the sun they will harden with a yellowish tint, and fully cured resin is very stiff.

I can sees some pictures here:


Great write-up, Damien. :smiley:

I’ve found that a lot of what you’ve written is pretty much what I’ve been finding as well. I haven’t left my prints out for 2 days, though lol. I should do that to a piece for some of the impact and heat tests. I really liked how that pocket monster came out, btw. The clear resin kinda makes it look a little creepy compared to the color render. lol

I learned a little about how much sun-cured resin can flex from my recent write-up, and the answer is “not much.” Some thin strips printed either didn’t print or printed distorted, and after curing were very brittle. They flexed some, but not enough to be useful for very long. Parts not cured in the sun flex more… gotta do more testing.

Reid: unfortunately, I don’t have access to an oven that I could use for non-food items, but if you’d like I could see about printing that part you mentioned. Could you drop me an email via my blog? (, a link in the column on the right)

Thank you TJ  -  email sent.


Is there an official property sheet somewhere?

If not I might be able to get some time on an Instron to pull some test samples…  For it to be significant I’d need to use a ton of resin though. (Especially since properties will depend so much on print direction).

I can certainly use the durometer at work to hardness test a few samples, need to go look up what a test coupon is though.

I was thinking that someone might want to cure the resin using something other than the printer if they’re going to test it.

I was thinking a glass tube filled with the resin and left in the sun (or in the light of a UV lamp) would probably have uniform properties. Hopefully the glass would break away.

For what it’s worth, I just did my first print, and was surprised by how flexible the part was when I started removing supports. I sat it in the sun for a couple of hours and it stiffened up some, but it’s still pretty wobbly in the thin sections. I also noticed some yellowing, especially in thicker sections. Is that something that keeps increasing as the parts age?

Despite being rinsed repeatedly with rubbing alcohol, it still feels a little sticky, Is there anything else people wash their parts with?

I’ve tried washing parts in 91% and 99% isopropyl alcohols, and the 99% does a much more efficient job and dries quicker with a less slippery surface. If you’ve noticed the part getting kind of cloudy while it dries after the alcohol bath, that’s the water content trapped in the alcohol-softened resin that hasn’t evaporated (if I’m not mistaken, anyway).

I find it helpful to use a makeup sponge to gently rub the excess stickiness off in the alcohol bath, and leaving it in the sun for longer periods of time also helps. Leaving the part in the alcohol longer than the recommended 10 minutes only soaks and expands the part further, which can cause cracking as it dries.

Damien has left some of his parts out in the sun for 4 days (check the blog post he linked to above) and he mentioned that it yellowed more the longer it was left out. I’d be interested to know just how yellow parts get… time to put a test part outside. ^_^)