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JohnInOttawa

Has anyone tried this?

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Good afternoon everyone.  Just wondering if this will work or if it is a very bad idea.

 

I have a model that I need to be strong and relatively ridgid in more than one plane.  it's pretty tall, just about the entire height of my UM3 volume and narrow enough that I am worried that significant leverage could result in a break along a print line.  I really don't think infill geometry is going to do enough for me.

 

I was recently working with some low viscosity, relatively low temperature curing epoxy on a woodworking project (stablising spalted maple internals for a table) and it occurred to me, what if I printed a grid infill and, before I got to the point where I started to skin the top, I paused the print and filled in the infill columnar gaps with this epoxy.    If this worked, I would further like to experiment with suspending reinforcing fibre or steel wire in the epoxy columns, much like rebar.

 

I will, of course, make a test run and fill it with the expoxy once removed from the print zone to test for watertightness and to make sure it doesn't just melt everything, but I thought I'd see if anyone here has tried such a thing.

 

Would it do as I expect, and harden into may vertical bonded expoxy rods, or would it ultimately fail?

 

John

 

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Could you rotate the model 90°, so it is laying flat? And then print with 90% or 100% infill? That should give a quite stong part.

 

For casting epoxy into a print, I would rather use no infill at all. Otherwise the infill grid might create weak points where bonding to the epoxy is not very strong, and where air bubbles are entrapped. Another thing to consider might be shrinking of the epoxy, which could deform the model, so try to find a slow-curing, low-shrink and low-exotherm version.

 

But if you plan to use epoxy anyway, what about designing and printing a mould, and then casting the epoxy into it? At least, if the shape of the model allows this (=not too complex, no impossible undercuts)? Then you would have a part in one piece, in one single material. And the mould might be reusable. Also, it might be easier to incorporate fibers or steel wire into it. Only make sure you get *very good* release methods, in multiple layers, so the epoxy does not stick to the mould.

 

Or else, what about printing a single piece of the model, then post-process it and make it nice and smooth, and then cast a silicone mould around it? And then cast the epoxy in the silicone mould? This gives less release problems, due to the non-stickyness and flexibility of the silicone. But still use plenty of release spray, to ease releasing and to prolong mould life. There are lots of good Youtube videos on mould making and casting. Probably this is the method I would try, if I had to do it. This method combines the advantages of 3D-printing with those of silicone moulds and casting.

 

If you have succes, or failure, don't hesitate to show the results here, so that we can learn from it.

 

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Good feedback @geert_2, thank you!

 

Your reflections on alternatives make sense.   My thinking in this case was to have the part come off the printer in a state where, after curing, it would be good to go with minimal post processing.  Your points on the weaknesses introduced by the infill echo a similar engineering concern on shear lines.

 

I did consider alternative placement, there are some constraints on doing that, such as printing a sloping surface without a big alias effect and a full length bore for a rod. 

 

That said, I am looking into mold options, there are a few threads here on filament choices, around here it looks like I am down to moldlay or printable wax.  May have to do a bit of trial and error there.

 

Thanks again, appreciate your help!

 

John

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