Flexible 80A discolouration on some prints

I’ve been using Flexible 80A material to make a coupling for a test jig, which has been quite successful. I have noticed that that the part is discoloured, with half of it having a yellowish hue and the other half appearing a to be purple.

This is the print orientation I used, with 0.1mm layers.

When the print is completed it is washed in the Form Clean (IPA) then dried using low pressure compressed air, followed up by 10min @ 60degC in the Form Cure. At this stage the discolouration is able to be seen.

The previous components I have printed in Flexible 80A or Elastic 50A have a yellowish hue to them, but as a single uniform colour.

Has anyone else had this experience with this material?

Try not to dry them with compressed air. go from IPA to cure right away. it could be oxygen molecules are interacting with your model during cure

Perhaps. Curing it inside a glass filled With water?

Any clear resins will always turn a bit yellow after cure but it should be uniform so it’s odd they are partially discolored.

It sounds like they weren’t discolored prior to curing?

I know that with Elastic resin, if parts aren’t completely dry and you cure them under water some spots turn white. Perhaps your parts aren’t completely dry of IPA. I would make sure they sit out for half a day at least and then try again.

Curing under water doesn’t affect discoloration, it only makes parts less sticky because it displaced oxygen at the surface and allows the surface to cure fully.

The yellow/purple effect I’ve noticed seems to be a light diffraction effect - particularly under large spectrum like daylight - lesser with artificial/fluorescent lighting etc - it’s not that is it? In my limited experience from memory it doesn’t seem to be as prevalent pre-cure as to post-cure…

Hi @stuartc,

Thanks for getting in touch. In addition to the suggestions the others have made, I would also double check that the resin cartridge is shaken up before printing, and that the material in the tank is mixed thoroughly. It’s odd that only some of the part is discolored, so making sure the resin is uniform is worth a try. If the discoloration persists, feel free to get in touch with Support for a closer look.

Thanks for all the feedback. Lots of good suggestions to follow up on.

Since my initial post I have printed a different part that does not exhibit the same sort of discoloration, the entire part has the yellowish hue. So I now suspect that the support structure of my original print - that is where the print remains purplish - is obscuring the IR a little whilst curing.

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I am about to use Flex resin for the first time making some flexible tubing.

I’m trying the same thing with some proprietary pressure hoses in 80A. They’ve been failing spectacularly…

My houses were much smaller see photo of AC unit for NASA Rocket car in O-scale (1/48)

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hoses not houses!