My Curebox automatically defaults to 30 minutes @ 45C for Tough material. This seemed to work pretty good although admittedly I didn’t do much failure testing, dropped a few pieces onto concrete from chest height. After a few drops they’d fail. I was on the phone with Formlabs and was told 60 minutes @ 60C was what they recommend, and that parts would be stronger.
The parts I’ve cured at the higher temp and longer time are noticeably more green tinted than the Curebox default settings. They are also exceedingly brittle I discovered, one part that I would consider pretty stout if printed on our FDM machines shattered when I dropped it just a few inches from my hands onto my desk while working.
How do your Tough prints respond to different curing? Because mine are really…not…tough
I do not have a curebox, I just have the homemade version with the nail curing system.
My last 25 prints have been almost exclusively in tough.
Although I have never conducted any thorough drop tests, I have dropped and even thrown a few across a room and have never had one break. I am sure breakage also has to do with geometry. A larger, cup sized item with thin walls probably has a higher likelihood of breaking than the smaller, thicker items I print.
FWIW I cure my parts for about 30 mins. the nail solution doesn’t throw off much heat, nor can I check the temp.
You might want to move to the Durable material if you are looking for impact resistance. Note that the modulus of elasticity is going to be lower, so you’ll need to account for that in your design.
There is also the new “Rigid” resin that looks pretty interesting - can’t wait to try it out.
As for cure times, I have been using the default Curebox settings (which are the same as yours). I have no doubt that if you subject it to longer cure times you are going to get a more brittle (but stiffer) part. I don’t think the temperature is as critical as the cure time.
You might also try a water cure - submerging your part in a glass water tank. It has helped me get better and more consistent cure results.
Have you found a better cure in water, in the cure box?
The parts I’m making are followers for a rifle magazine, the most impact they’ll be subjected to is the spring tension on them, and the recoil from the rifle.
These parts cured at 60C for 60 minutes are seriously brittle, moreso than prototype parts I made from clear.
I actually have some durable material I may try, but my worry is that it has an extremely low operating temp…I was told 110F max, which just leaving a part in a car sounds like an issue.
If your parts are that brittle, then they have probably cured too long.
If the parts are held in tension for very long, you probably don’t want to use Tough or Durable - you will definitely see some deformation. Especially in the summertime. Neither material has a great response to temperature or continual loading.
You might consider trying to cast your parts in a urethane for better results. You can print the molds using a standard resin.
I will try some water curing and report back. Most of you probably aren’t intimately familiar with rifle magazine parts, but specifically the part I’m having issues with is for a bolt action rifle, and under fairly low spring pressure. Low enough you can easily push the spring with a finger.
My gut tells me this material should work for the application, based on some videos I’ve seen demoing “Tough” toughness. I think an FDM printed part from PLA would hold up just fine honestly. I’m printing replacements for folks out of polycarbonate right now as a quick fix until I figure out what’s making these SLA parts so fragile.
60 minutes @ 60C is our recommended curing specification and the change in color is perfectly normal and a good proxy for establishing whether the part is fully cured. As @kevinduhe mentioned, Tough Resin does tend to have a higher subjective impact resistance than you’re seeing.
Are you referencing this curebox? 60 minutes @ 60C is the recommended profile using Form Cure, but Wicked Engineering’s curebox may have different exposure values and require different settings. If that’s the case, you might iterate through a few settings to see which work best for your prints.
Yes that’s the UV oven I’m referencing. They are 365/405nm wavelength, and recommended 45 degrees for 30 minutes on Tough. These parts feel slightly softer and are bluer in color, but still more brittle than I’d imagine.
I’m printing three now as a small batch to test three different curing settings today. I’ll print more overnight to test curing in water.
I just got more cartridges in the mail today…I had some issues with my first two cartridges saying they were worn out long before empty. I wonder if that could have any impact on the material…probably not, but I guess it is a variable.
Maybe it’s just the photo but my Tough parts look much greener after 60min in the Form Cure, maybe that’s why they didn’t break as easy ? My gut feeling is that the biggest part you showed should have failed the first and second tests. I dont’ think @mkmachining’s parts are over-cured, I think yours are underdured.
My parts have a minimum feature thickness of well over 3mm and are not nearly as durable as you’re describing.
That being said I shot some video last night of some redneck science. I cured 3 identical parts for 20, 40, and 60 minutes at 45*C with wildly different results. Will post in another thread. All my parts looked more “blue” than 60 minute, 60 degree cure. They were printed in open mode, which I’m not sure if that would make a difference.
I meant to mention color, it escaped my mind. I have never experienced a green color. My parts are always blue just like the pics above. So my parts are not cured enough, yet stronger?
Well, stronger is a broad term. Under-cured parts can be bent more before breaking , but may need less force to bend to the breaking point. Properly cured parts can bend less but require a bigger force to reach the point where they break.
Mechanical properties of plastics are pretty complicated to manage and they can be strong in many ways, they force you to make pretty big compromises usually : If for you “strong” is “impact resistance”, then Durable is more indicated… but then you won’t be able to put too much torque on these fine threads or you will mow them flat. Just like you won’t be able to break a chewing gum by throwing it from a building but you will break a marble by dropping it 15cm, which one is stronger ?
The real issue here is… will a part stay “uncured” ? and for how long ? I have had tough part that were under cured and after a few weeks/months they turned more green (natural light is also comprised of UV). Then there is dimensional accuracy, I really get the best dimensional results when following Formlabs recommended cure settings since the printer is calibrated for the end results under these conditions.
Interesting results. I still have never experienced tough parts breaking apart like yours. I have had the standard resin break from a chest high drop, but like i said above, it took a hammer with multiple wacks to get a small crack.
The big difference in our curing process is the heat. Using a home-grown nail curing system, I am certainly getting the UV light but little to no heat compared to the Curebox.
@JohnHue I have a few of the same parts which have been on my desk for a few weeks. Still the same blue color. If I have time today I will conduct my same non-scientific tests to see if they still stand up.
So I took one of my parts which has been sitting on my desk for about a month (my desk sits right next to a window). Conducted a chest high drop test, it was fine. Then threw it against a brick wall. It broke on the second throw. I think if you need impact resistance, under curing tough is the way to go…that or go with durable.
I wonder how the temp resistance changes. Durable only being good to like 100*F hinders my uses. That being said I am printing the same part from durable to send to folks that had a brittle part before switching back to Tough to crank out a bed full.
