Today, I came across this video which shows lost pla being done using silicate bound sand as the investment. Have we seen this method here before? Anyways, this sort of thing is completely out of my wheelhouse, I'm just sharing because I found it interesting and hope others do as well.
Thanks Rocco, neat video! Looks like there could be some test and tune on the printer to reduce stringers and improve surface finish. I thought the wires and selective re-packing were clever.
I did something similar a couple years ago using undrafted PLA patterns sent to me. I made Sod Silicate molds and put the molds in the oven at high enough temp to shrink and soften the PLA which I then lifted out easily despite the lack of draft. Worked well with good rendition of detail and dimension. Denis
Isn't 10%-12% SS a lot? I thought 1%-3% is more or less normal for cores. I believe that if you go over 5%-8% it more or less turns sand/SS into something on the order of concrete - even after the heat cycle of casting. Does he need that much SS because of the burnout cycle? Maybe room for experimenting there, so that you get something that holds together thru burn-out and still gives an easier shake-out? Don
It might depend on the grade of SS being used, if you're using a SS intended for core making, 3% may be the appropriate amount. The SS that's locally available for me comes from a pottery supply house and it's N-grade and is not generally recommended for core making. I experimented with it a bit, I started at 3% and that made very weak, completely unusable cores, the sweet spot with the N-grade SS turned out to be 6%, those cores were strong enough to handle but still easy to break out of an aluminum casting. If you're interested, here's an old video of me making a core with that N-grade SS mixed at 6% by weight. BTW, when I found a mix that worked for me, I stopped the experiment so I really don't know how a 10-12% mix would behave.
Don, I did not watch the video. I've made lots of Sod Silicae cores for iron. I use 5% RU SS that has been mixed so that it is weakened with 15% sugar and diluted with 15% tap water. If I forget the sugar (did this once) the core is hard as concrete and extremely difficult to remove. Here is a thread in which I did a sort of lost PLA method.: http://forums.thehomefoundry.org/in...itate-removal-from-sodium-silicate-molds.808/ Here is a thread on SS Core making.: http://forums.thehomefoundry.org/in...e-making-in-cast-iron-molding.702/#post-14902 Denis
Denis: I'm assume the the sugar is 15% of the weight of the core, is the 15% tap water a percentage of the core weight, or the sugar weight? Don
No. SS 100 gm, table sugar 15gm, water 15gm as the basic SS mix. Add 5gm mix to 100gm sand. Als0 add 6gm sea coal for iron core to aid finish. Use CO2 gas to set or add .5gm (10%) propylene carbonate to SSmix as a catalyst. Denis
