Issues Printing Models with Print-in-Place Hinges, other forms of articulation?

[lconover]

I’m having a heck of a time troubleshooting an issue with a model that uses print-in-place hinges and articulation pins.

It’s a adorable articulated dino that is designed to print without supports on a filiment based 3d printer. (Link: https://3dkitbash.com/products/boon-the-tiny-t-rex )

While it printed cosmetically beautifully on the Form 2 in Formlabs Clear Resin, I’ve run into a slew of problems when attempting to assemble the parts together after I had cut off all of the Preform generated supports. Boon’s head is designed to have a print-in-place hinge to allow for posable eyes to be inserted. That part, while we can visibly see in the clear resin where the hinge should… hinge… doesn’t. Every attempt we’ve made to get it to separate - X-actos, brute force, etc - have resulted in nothing aside from broken Boon heads.

There’s also several hook-shaped pieces that loop around other parts to create points of articulation. We’ve had issues where these pieces would shatter when we attempted to assemble them onto the legs of the model. I’d debated trying to do some assembly steps with partially cured resin since it’d be softer, but I didn’t want the joints to glue stuck in place when curing finished.

• Am I just using the wrong resin? (Clear might just be too brittle?)
• Do the points of articulation need to be tweaked in some manner to be printable on the Form 2? (IE: Print in place hinges - do they need larger gaps?
• Is there perhaps some liquid resin pooling inside those hinges, gluing them shut when I cure things?

Any expertise folks care to lend would be hugely appreciated, because I’ve always wanted to print high resolution, articulated pieces like this.

[Zachary_Brackin]

You’re not going to be able to print parts together that need to move without adding a significant gap between them.

The issue is that there’s a certain amount of indirect curing that happens, the laser spot will scatter a bit within the resin and areas where the resin doesn’t easily drain will get repeated exposure and can fill in the gaps between pieces. Also, there’s no way to stop the laser from curing beyond the current layer, so surfaces on the undersides of parts will have some extra material there which can also contribute to filling in gaps depending on the orientation of the object.

[lconover]

Thank you so much for the insight. I think I’m going to have to learn how to ‘flap’ open that model in an editor to get it to print the living hinge successfully. (Or hopefully the designer will be willing to help me with doing so since I paid for the design.)

I’ll have to see if there are any design documents that Formlabs provides on how to best go about designing those kinds of print-in-place elements like living hinges, etc. There’s a lot of models I’m dying to print that have those kinds of elements that may need tweaking. (And I’m going to have to get over my fear of learning Fusion 360, I suspect., to do it.)