Molding

The next part of the process is where we start getting dirty. The bottom pattern is placed flat side down on a flat board. The flask is now set around the pattern. The flask is the wooden or metal box that the mold is made in. It has two parts the drag (bottom) and the cope (top).

Patt Flask

The part and the board are coated with a parting agent (I am using talc or chalk). Excess agent is then dusted off the part with a soft brush. The parting agent keeps the sand that will be added next from sticking to the pattern and the two halves of the mold.

Part Flask

The sand that gets added now is called petrobond. It is a mix of fine sand, clay (treated to absorb oil), and a very tiny amount of oil to help it all stick together. The sand is sifted through a screen to only allow the fine unclumped sand to touch the pattern. This is only done for the bit of sand that is next to the pattern. Once the pattern is covered sufficiently it’s packed down lightly and more sand is dumped into the drag. The sand is packed and added until the drag is full.

Drag Striking inProg

Striking off the drag is the last step in this process.

Drag rammed

The drag is flipped over and the cope is set on top. The second pattern half is attached to the first via the pins.

Cope

The process of covering the pattern in the parting agent, brushing, sifting sand, and packing is repeated. Two tubes were added when I did this. The smaller tapered one is the sprue, where the metal is poured. The other tube is the riser, where the reservoir of metal goes. This is needed because as the aluminum cools it shrinks the riser will stay molten until after the part has solidified (If we do everything correct).

Cope Ramming inprog

 

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