Walking Dead Chess Men
Today I poured 3 cylinders of brass to make 12 chess pieces. 8 pawns and 4 rooks. It was a total failure.
A model engineering friend had donated 3.3kg of brass, in the form of spent cartridges.
This is the first pour which I have done in 3-4 months. It was ambitious, requiring 3.25kg of investment powder, and 3 large cylinders. But these pieces will all be redone, with new 3D prints, and recasting. The failed pieces will be remelted.
I think that the main problem was that the investment mixture which I painted onto the prints was too thick, and did not penetrate all of the surface features. And the painting was not adequately thorough, leaving bare areas which predisposed to bubbles.
And the main bulk of the investment mixture was too thick. I did mix it a bit longer than usual because of the volume involved, and I did notice that it seemed more viscous than usual, and when vacuumed, the bubbles never really stopped coming.
The voids occurred mainly at the bottom of the cylinders, which indicates I think, a need for ventilation tubes. I had stopped using those for bronze pours, but maybe for brass they are necessary.
So, at this moment I feel that it was a wasted day. But I have learned some things, and have a plan for the next pours.
And I was very satisfied with the quality of the brass from the cartridges. Hopefully that will continue as a source.
Hi John. Good try. Your 3D print material left too much ash in the mold. You need to use a castable resin. You should check out the Creality 3D printers that use resins. They work OK but are tricky to get the parts from in castable resin. The resin burns to nothing though and are as good as wax. Detail is really good. I use them on my cannons.
Hi Zane and thanks for the suggestion. I had not considered ash as a possible cause. Most of my castings using lost PLA have worked well. Something was different with the chess pieces, and I am still thinking that the painting with too thick investment was the most likely culprit. A resin printer would be nice, but I am trying to avoid buying more stuff than absolutely necessary.
Which printer do you use? Do you post any pictures of your cannons?