Advice on UV Resin Curing for 3D Printed Cosplay Helmet

Hello fellow crafters,

I've taken on a project for a friend and am currently in the process of 3D printing a cosplay helmet. I'm trying to avoid the typical route of bondo or putty and endless sanding, and instead, I've decided to give UV resin a try.

I invested in a specific UV resin curing lamp which I've seen used in several YouTube videos on similar projects. Alongside this, a friend generously gave me some UV resin which I applied in a thin layer using a sponge. To eliminate bubbles and thin out the layer, I used a heat gun.

To ensure an even cure, I built a small curing box out of a plastic container, lined with aluminium foil. A little turntable was added to the mix to slowly rotate the helmet during the curing process.

Before going all-in on the helmet, I ran some tests to ensure the resin cured well. When I applied a small pool of resin on some cardboard and put the UV lamp on it, it cured within a minute, leaving a half-millimeter thick surface. This seemed promising.

However, when I applied the resin to the actual helmet and left it in the curing box for anywhere between 10 to 50 minutes, the resin did not appear to harden correctly. Even after two sessions of 10 minutes each, it remained sticky to the touch. If I run my finger over it, some of the resin even comes off.

I also tried to cure the helmet in direct sunlight for a few hours, and while this seemed to work slightly better, it still left a tacky surface that did not feel completely hard.

I decided to test a different type of resin, which cured even better on its own, leaving a circle of a one-millimeter thick surface when directly hardened. However, this other resin displayed the same symptoms as the first one, not fully curing even after prolonged exposure in my UV curing chamber.

So, I'm turning to you all for help. Can anyone explain why this is happening and possibly offer some solutions? I'd greatly appreciate any advice or guidance on this issue.

Cheers
F.

... sunlight should cure UV-resins instantly - if there too is a "soft" film, then this is Oxygene-inhibition, whats common with most resins, if stored in normal ambient.

With your cahmber - it coud bee, the light/energy-density isn't sufficient ... industrial grade UV-curing boxes use up to some hundred(!) watts of 405nm UV-light or less for shorter wavelenghts ...

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Viktor
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interesting, but wouldnt that apply to normal resin print curing as well?

i found a video of a cosplayer that describes that effect as well.

interesting stuff. thanks for the hint