Though V3 resin model broke like glass


Recently I had my first real problem with printed part. Plastic broke like glass. Other parts of the model are not compromised. Snapped surface is ultra smooth and feels as broken glass.

This has never happende to me before. I usually test rigidness of the parts with hands. One hand of the model snapped very easily with very low force. As you can see in pictures, before force testing, there are no visible error lines on the model. Also the other hand is perfect. I tried to snap it off with full hand force, but it’s rigid, like it should be. It does not snap off, but it does slightly deforms. So that’s normal.

Resin was Though V3 in the tank, but with Though V4 added as new cartridge. I know I should not make this normally, but mixing T V3 and V4 should not be a problem according to this post: Phasing out Tough V3

I used Form Wash (20min) and Form Cure (60°C for 60min).


As you can see, it snapped off right at the point of support. Was this some kind of print error? Did this happened to someone else?
Just wanted to figure out what went wrong, so that it does not happen again.

I printed another one, but change orientation with no need of support for hands. Came out perfect.


Did you cure it too long? The more UV it gets the more brittle it gets. I have had parts that sat on my desks for months get knocked off and they shatter like glass when it hits the floor. New parts usually are brittle though.

Print was fresh. I made it last week.
I accidentally broke it after curing when it cooled.

I don’t think I cured it for to long. I followed this guide:
Cured for 60min at 60°C.
And yes, the table in Form Cure did turn when curing, so that curing should be uniform.

Also. Preform, Form 2 and Form Cure are all updated to the latest versions.

Hello Matej1990,

If you are still experiencing this problem, please reach out to us here. We will gladly investigate this.

Have a good one!
Formlabs Support

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