Help me cure!

New to SLA
I just started printing and in doing so i am wondering how my curing process is.

  1. Im curing using 400nM lights (i purchased the wrong bulbs initially). Instead of purchasing more and waiting i have started using them. Are my prints going to cure properly under this light?
  2. Im using 99% alcohol for my rinse/soak cycle. Is the 99% going to have any ill effects on my prints.
  3. Using ‘Tough’ resin
  4. I’ve been curing for roughly 2 hours + or - 20 min. With thinner walled prints is this acceptable or should i be curing for longer since im not using the proper lights?

Any advice would be appreciated.
Thanks in advance people

Welcome to SLA :slight_smile:

A great number of people here are using the nail salon solution for curing their parts (I am one of those). Those bulbs are actually 385nm.

I too use mainly tough resin, and I too use 99% IPA. Leaving your parts in IPA too long (especially 99%) can adversely effect your parts, so make sure you aren’t soaking them much past the 10 min x 2 rule. Also make sure they are thoroughly dry before curing.

I tend to undercure my tough parts. I feel they are stronger and more durable. Take a look at the video by @mkmachining here. Judge for yourself.

  • Kevin
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THANKS for the reply
For drying are you just wiping down the part a bit (paper towel? micro fiber cloth?) and letting it sit for a few before putting into your cure box?
Thats one step i have been missing is ‘dry-time’.

I think it is recommended to let it completely dry at least a couple of hours or more. I am never that patient, however. At the very least I wrap my parts in a few paper towels and bang it around to make sure I knock loose any trapped IPA, and then wipe it down the best I can. Normally I will let sit for 15 mins or so, but not always.

EDIT: Note my prints are almost always mechanical engineering parts and not for display or sale. Curing while the part is still wet with IPA can damage the part, especially as far as aesthetics go. If you are printing art pieces, or items that are going to be sanded, painted, etc. I’d recommend allowing them to fully dry before curing.

To add another perspective :

I never let my uncured parts wait to dry them, but I blow them with compressed air until there is no IPA on the surface anymore. They are still a bit tacky wen I put them in the oven (I have a Form Cure but was previously using a home-made box).
I personally believe Formlabs recommends to let the parts dry before putting them in the Form Cure for safety reason (putting a part soaking wet from IPA in an enclosed area with electrical stuff is a fire hasard), I yet have to see an official comment denying that or see any ill effect on the parts.

The most important factor isn’t the exactness of the wavelength of the light (400nm will to just as wall as 405, the indicated wavelength is just a nominal value and the actual light does spread quite a lot), but rather the temperature. Maintaining your parts at 60°C is a very important step as it allows the resin to cure deeper which can’t be achieved by just curing at 20-25°C. This is also the only way to guarantee that your parts have the mechanical properties given in the material’s TDS.
For Tough parts, 30 to 120min at 60° is what you should aim at, with 60min being the recommended value and 30min an unofficial way to achieve a better impact resistance while sacrificing flexural modulus.

There is no ill effect on the print with 99% IPA, just like with other concentrations you should not leave the part more than 20mins (Formlabs recommendation) of there is a risk that they will deform.

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