How 100% is 100% infill?

[Rocket 1]

I'm printing some parts that are the fairing for a submersible robot.  They will be under quite a bit of pressure and I don't want any air pockets.  It got me wondering, are 100% infill parts truly 100%? Does the molten filament fill any gaps on previous layers or will there be some gaps?  It isn't critical if the pieces deform a bit underwater but it would be nice to put my mind at rest that it'll only be small deformities (or not!)

 

Thanks,

Toby

[dxp 23]

37 minutes ago, Rocket said:

Does the molten filament fill any gaps on previous layers or will there be some gaps?

It depends. See lets-make-something-clear to get an idea of how 100% it can be.

From my engineering-point-of-view and after some airtight, fine-sanded parts: 100% is solid. No problem under water.

[limeyboy 0]

I had a look at the link dxp posted and that material looks interesting, based on 2) below I may investigate.

 

Couple of data points with T-Glase:

1) I made a model boat (T-glase) and sat it floating on top of the water (so no pressure admittedly) = 24hrs later it was still dry inside.

2) I made a vacuum chamber (T-glase) and it leaked pretty badly for what I needed - could not get the pressure below 40mbar absolute. So at that pressure differential (call it 970 mbar) the gas load coming through the walls was defeating the small vacuum pump capability and the pressure stabilised at 40mbarA.  I ended up painting the T-Glase with basically super glue while the chamber was under vacuum so the glue penetrated, set and sealed the gaps. It then was able to be evacuated to less than 1 mbarA which was good enough for that trial.

 

So - with T-Glase - 100% infill is definitely not actually 100% and my trials above show that T-Glase solid walls are not actually solid - but it depends on pressure differential etc as to whether it will do what you need. However, maybe the material dxp posted makes a big difference and will work for you without needing any post-print-treatment....

 

Good luck - sounds like an interesting project.