Watertight means the part will hold water without leaking. Here are 5 parts I've made that originally leaked water badly. (PS: I also made the bowls in the background before I got started with 3D printing.)

How to make PLA parts watertight

The reason for the leakage is that 3D printers leave tiny gaps in between the loops of plastic they lay down, and water can get through these gaps. The solution to this problem is to seal the gaps. But how to do this?

With ABS most people use acetone. It is a solvent for ABS and a light coating is enough to literally weld the adjacent loops of plastic together. But acetone does not work with PLA.

There is a chemical that does work as a solvent for PLA; it is called tetrahydroflouane (THF). This is a rather nasty chemical that can cause serious injury and must be used very carefully. Fortunately I found another one that seems to work just as well - dichloromethane (DCM).

This is a small can of DCM I got at Amazon:

How to make PLA parts watertight


It comes in various sizes; I got the smallest one to test with. DCM is not a very nice chemical either, but it is not as bad as THF. It looks like water but is highly volatile - even more so than acetone. I suggest using it only outside or with a fan blowing on and away from you. I used the small brush in the photo to simply paint the DCM onto the part. It dries almost instantly. So I put on roughly 2 - 3 coats which actually takes almost no time at all.

I'd be interested to hear is anyone else uses this to make their parts watertight.

March 14, 2016

Birk Binnard Birk Binnard
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