china Sand casting technique

Sand casting uses natural or synthetic sand (lake sand) which is mostly a refractory material called silica (SiO2). The sand grains must be small enough so that it can be packed densely; however, the grains must be large enough to allow gasses formed during the metal pouring to escape through the pores. Larger sized molds use green sand (mixture of sand, clay and some water). Sand can be re-used, and excess metal poured is cut-off and re-used also.

Typical sand molds have the following parts (see Figure 2):

• The mold is made of two parts, the top half is called the cope, and bottom part is the drag.
• The liquid flows into the gap between the two parts, called the mold cavity. The geometry of the cavity is created by the use of a wooden shape, called the pattern. The shape of the patterns is (almost) identical to the shape of the part we need to make.
• A funnel shaped cavity; the top of the funnel is the pouring cup; the pipe-shaped neck of the funnel is the sprue ­ the liquid metal is poured into the pouring cup, and flows down the sprue.
• The runners are the horizontal hollow channels that connect the bottom of the sprue to the mould cavity. The region where any runner joins with the cavity is called the gate. 4
• Some extra cavities are made connecting to the top surface of the mold. Excess metal poured into the mould flows into these cavities, called risers. They act as reservoirs; as the metal solidifies inside the cavity, it shrinks, and the extra metal from the risers flows back down to avoid holes in the cast part.
• Vents are narrow holes connecting the cavity to the atmosphere to allow gasses and the air in the cavity to escape.
• Cores: Many cast parts have interior holes (hollow parts), or other cavities in their shape that are not directly accessible from either piece of the mold. Such interior surfaces are generated by inserts called cores. Cores are made by baking sand with some binder so that they can retain their shape when handled. The mold is assembled by placing the core into the cavity of the drag, and then placing the cope on top, and locking the mold. After the casting is done, the sand is shaken off, and the core is pulled away and usually broken off.
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  Sand Casting

  Green Sand Casting 008

  We supply big sand casting parts to your specifications. All the products above are what we've supplied for our customers before.  sending me your specific drawings as well as technical requireme ...
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  Green Sand Casting

  Green Sand Casting