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I am looking to 3D print some small molds that will allow wood glue to dry but not stick.

Is there a recommended filament that is known to resist binding to simple wood glue?

Alternately, is there an inexpensive adhesive (like wood glue) I could use instead that will not stick to the 3D printed mold?

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  • $\begingroup$ Flexible filaments like NinjaFlex, PolyFlex or TrueFlex might be useful. They probably need a good mold release agent. $\endgroup$ – Perry Webb Jan 22 at 15:35
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You are looking for a filament that does not bond to wood glue, or as weak as possible. You misunderstand how wood glue "bonds" to plastics:

Wood glue is typically PVA. It bonds to wood and paper by seeping into them before curing and hardening. The mesh of the glue entangles fibers of the wood/paper and itself, bonding with not only the exposed surface but also with material up to the depth it penetrates.

When such a glue is applied to a typical print surface, it seeps into the cracks and through print imperfections but does not penetrate the print to the same degree as it does in the open wood fiber setup. It clings to the surface and only bonds - if it does - only to the surface layers. The same effect happens when you cast resin into for example a silicone mold: there is much less chemical bonding, at best at the interface, and quite some interlock.

To prevent such, two things should be made: first, you need to smooth the mold as much as possible and have all the angles right. It might be easier and faster to coat the hard molds in a smooth lacquer, which not only removes the creep areas but also acts as an interlayer, making release easier.

Then, you should use a mold release agent. Mold release agents come in many shapes: I have seen Talcum Powder being used effectively for both metal as well as cold casts, if the shape of the mold was well made (no undercuts, no unpowdered areas). Easier to apply are usually mold release sprays for many applications - careful, some are PVA based and would be the same as the glue you want to cast. For a concrete casting, I had used plant fat as a decent mold release agent.

What might be an alternative to wood glue depends on what you want to do with the finished product.

As far as materials that actively don't bond go, you could look into POM (Which is a pain to print and expensive - it's a bearing material) or nylon (also a pain to print).

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Considering my experience, SOME nylons don't bond to PVA at all. I tried at 70 °C and 110 °C and my nylon print can be pulled out from it manually with almost no resistance.

It's however difficult to know which type of nylon, since I used a trimmer line of unknown composition (except that it should be mainly nylon).

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