So... first try to make the the first core was not fully sucessfuly I tryed to open the corebox after ramming the silica sand and realized, that it can't get pulled out of the corebox without damaging the core. But it was not hardened. So next try would be hardening the sand in the corebox nd try it again. I think the hardened core will brake st one point but then it will come out and could be glued together again. So I hope that works...if not, I have to change some little things on the inner Part of the corebox. But, it's a little sucess for me
Why did the SS not harden? Are you using CO2 or catalyst. Was the ambient temp cool---really slows down the catalyst. Waxing the corebox several times can help removal. SS will interact with many coatings of coreboxes---I think your prior post says you used "clear coat" as the final coating. Lacquers, even when reapeatedly waxed react a lot with SS. Epoxy does not interact with SS. I suspect, though never actually tried, polyurethane varnish would not be reactive and 2-part automotive polyurethanes probably would not be reactive. Waxing and graphite powdering coreboxes aids release of SS cores. Denis
It did not harden, because i did not hardened it. It was only a quick test. Last night i filled the corebox once more and tryed to harden it with baking soda and vinegear to make co2. It worked, but the core was not fully hardened over night. This morning I tryed to pull it out and it workt great, but the spots where the core wasn'r hardened stayed in the box. I just ordered a bottle of Co2 for hardening...then I'll try it again. But, the inner part will brake the core when i try to get it out of the box. There are 2 or 3 spots where i have to redesign it or just split it in more parts and the try to hold them together with some sticks or magnets.
Second try You see the non hardened spots that srayed in the corebox. I think i used way to much Ss ... i read something bout 30% and today I watched som videos. There they say something about 5-10% Ss When I look at the pictures now, I think I was a little over ambitious making the whole Core for the Ports in one part. I think I could split it to more parts and then glue them together. What you all use for gluing Core parts together?
If you have some holes drilled in various parts of the mould you can directly apply gas to the non hardening area. It should work with 3D printed parts even if there's voids. I ended up adding a gas manifold to my sodium silicate patterns and drilling several holes to get uniform gas exposure. I found some shellac dissolved in alcohol and a generous amount of graphite added can be painted on to a mould with a brush and once dry can be polished to a high slippery shine that functions as a release agent for sodium silicate.
5% SS should be plenty. I use SS a lot to make core and have written several times in some details about successful methods. http://forums.thehomefoundry.org/in...e-making-in-cast-iron-molding.702/#post-14874 If you search this forum on "Sodium Silicate Core Making Melterskelter" you will find many suggestions on SS core making in many threads touching on this. Much of my method derives from Tom Cobett's excellent monograph on core making which I cited in the above thread. For aluminum you will not need to add sugar for weakening the core. To kick the SS reaction, I use Compressed CO2 with a plastic tube on the regulator and a piece of 1/8" OD brass tube on the end. I set the flow so I can feel a gentle stream on my cheek when the tube is an inch from my cheek. I use a nail to push holes into the molded sand to a depth a half inch or more from the inner surface and space the holes every 3 inches or so. I then insert the brass tube with CO2 flowing about a half inch or so into the hole and let the gas flow in for 10 seconds before moving to the next hole and repeating the process. I often flatten my hands over the surface of the sand as the gas is entering the mold so as to help keep the CO2 in the sand (may be totally unnecessary). I also use catalyst to kick the SS. It also works well but takes a few hours to set at 70F. Denis
That depends on the grade of SS used. I got some SS locally from a pottery supply store, it was N-grade, it's not really intended for foundry use and I found the cores made with a 5% mix were too week, I had to up the SS percentage, 6% seemed to be sweet spot, at that point I was able to make reliably usable cores. I do something similar, I either use a block of wood or a plastic cup to cover the open end of the core box and inject the CO2 through a small hole drill in the wood of plastic.
Back to the start... As I said, I was over ambitious. The first Corebox doesn't work as i planed it. The core, especialy the core for the ports is to complex to make it in one part. So I split the Core in 7 parts and print every part on it's own. Then I use the old way to make coreboxes. I will use moulding dental silicone shore A-45 for making the Corebox for every part. It's way easyer than trying to make boxes in CAD. I'll keep you updted with pictures soon
Last night my Printer did the ports, today I painted them. If anyone would like a good thick paint and knows someone who sells PPG paint, I can higly recomend their "Selemix - Direct Mix" in 10% gloss. It sticks to every material without any primer needed. It's a high build paint and can allso be used as filler. Resistant to all chemicals. NEXT STEP: Print the rest of the core parts
Core print is finished. Most parts are split in two halfes. This week I will paint and sand everything for smoothenes and the the "silicon games" will start
A little Update: I spent some Time on trying to make core boxes... but it seems to be allmost not possible. The core is too complex to make a silica sand core with classical coreboxes. So I get in contact with a german foundryman who does castings for his track pull engine. He is on youtube too and he is a verry nice guy who will help me. We decidet, that it would be the best to do it with investment technique. So print the whole cylinder split in 4 parts in PLA or Polycast filament and then do the investment casting. He allso invented me to some nice german startup guys, who offer a investment ceramic slurry and they allso will help me. Bur first I have to fix my 3D printer...it quit his job right before new year and I'm nearly done with it. I'm not willing to invest again more and more money to fix it. I'm thinking of saving some money and buy a good printer. (BambuLab) Next thing is... the company I'm working for is quitting...so I lost my job and have to find a new job before I can move on with this project. Time will show...
Hopefully things will sort out for you soon with the job and printer. I am glad you found some contacts for the casting portion.
