How to make metal casting molds?(1)

//How to make metal casting molds?(1)

We may need metal casting molds in many field. Do you know the process of manufacturing metal casting molds?

Cutting the Sprue and the Riser

To form the sprue — a passage through which you’ll pour the metal — measure the depth of the cope, and mark this distance with tape on the side of a section of thin-walled 3/4-inch pipe. Push the pipe straight down into the sand in the cope, in a spot where it will not hit the pattern. Twist the pipe back and forth to cut an opening through the sand, stopping when the tape mark meets the surface of the sand. Use a slick to carve a funnel shape in the sand around the pipe, beveling the edges of the sprue opening. Then slip the pipe out, with the sand core inside, leaving a passageway through which you’ll pour the molten metal.

On the other side of the pattern, form the riser opening — the passage into which excess metal will rise — by using a slightly larger diameter pipe to cut through the sand in the cope.

Venting the Mold

Use a 1/16-inch welding rod or a stiff wire (a bicycle spoke is ideal) to poke channels through the sand in the cope, so that hot gases can escape. Push the rod into the sand, stopping about 1/2 inch from the pattern. Make about a dozen vents over the pattern area.

Lift the cope from the drag and set it on edge, off to one side, where it will not be disturbed.

Removing the Pattern

Before lifting the pattern from the drag, firm the pattern edge of a water-based sand mold by moistening it with a molder’s bulb or a small brush dipped in water. This will help to keep the sand from collapsing when the pattern is removed. Screw draw pins into the holes in the back of the pattern and lightly tap the pattern to loosen it from the sand. Then gently pull on the draw pins, lifting the pattern straight up and out of the casting cavity.

Next I will continue to introduce the process of manufacturing metal casting molds.