Anyone has recommendation ho how to make a print (PLA or ABS) waterproof ?
Waterproof meaning that if the 3D object is a box the content of the box won’t get wet if the box is submersed in water…
In your slicer, be sure you have healthy infill for stiffness but more importantly, several perimeter walls to seal the model air tight… maybe 4 or 5. Also on top and bottom. You will need a flat area to seal the box and a gasket, like the head of an engine in a car has- very flat pieces that mate together with a gasket. You could print your gasket in flexible filament. The screw holes that attach the lid to the body should be surrounded by the gasket as well- again like a car engine.
Sealing the inside or outside of the print with two pry epoxy would further ensure its air-tightness but is probably overkill. I’ve even sealed things by pouring hot wax in over small pinholes… mostly for the fun of trying it. Epoxy is better
Brook
Nice Thanks @Brook_Drumm should be trying this in a few days/week.
To make something like a cup or vase or boat watertight, the most important thing is to get your extrusion volume dialed in just right. You need to calibrate the slicer settings so that you’re extruding the maximum volume that doesn’t cause failures – even over-extruding a bit compared to normal print settings. This will force plastic into the little voids between strands.
Here’s some photos showing what happens with under-extrusion:
Versus “normal” calibration:
Watertight prints need more volume than either of these show.
I recommend doing the volume calibration by printing 100% fill 20x20x10mm cubes and adjusting your slicer’s extrusion multiplier until you find the highest value that doesn’t end up over-filling the cube. This is more likely to give good watertightness than the normal “measure the single-wall perimeter width” procedure most people use.
With ABS, Acetone is always the answer. Use it on the inside of the box. That will melt all layers together and it should become waterproof.
A very thorough study has said anything over 70% infill is all the same strength… but I wonder what % infill becomes essentially solid, w/o the overlap causing issues w wall thickness and bad top surfaces. If you go 100% infill, underextrusion will be necessary to get a smooth top layer
For ABS, I would say to make sure you do not under-extrude and then you could use acetone one of two ways. One is making ABS juice and painting the part with it. The other is acetone vapor smoothing. There are also acrylic paints that might help. I did not try to make stuff water tight yet myself though.
@Brook_Drumm My prints are usually tough enough with 3 shells (1.2mm) l, 6 top/bottom layers (also 1.2mm) and filled to about 25-30% full infill. I wanted to try the “flex sealing” these days and tell you how it went @Andre_Courchesne1
@Brook_Drumm the “70% fill gives full strength” thing is for bending load, not tension. Bending stress is concentrated in the perimeters so infill just helps support the perimeters and doesn’t need to be 100% solid for strength. (Admittedly most real-world loads on printed parts are bending loads.)
For watertightness, you want the shells to be 100% dense, which is why you should calibrate extrusion volume at 100% infill. And yes, you can get good too surface quality at 100% fill if you calibrate extrusion volume for 100% fill printing, not for single-wall perimeter thickness!
Ryan- you are right on all points. It’s more clear how you explained it.
One other approach that I find helpful is to go through the learning curve of using a larger nozzle. I’ve become proficient at .75mm and larger tips. The slicing is a little nuanced but is straight forward. The overhangs at lower layer heights is far better- up to 70 degree angles as .2mm layers! But small details and ultra sharp corners are sacrificed. The big benefit is functional models print way faster and if you can get used to .5mm or .75mm layer heights, print time plummets, layer adhesion and watertight walls come easy. Far less infill is needed and you stop worrying about strength and start thinking through internal support and any sag you might get on top surfaces. My prosthetic printer produces hollow prints that are massively strong at a fraction of the print time. It just reveals layers at those settings but mentioned. But for me, faster is way better.
Brook