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Riser Design

Riser Design. Riser is a waste part, as it will be separated from the casting body after the mold is destroyed and reused for casting (for expandable mold casting). To minimize the waste of material, it is desirable for the volume of the riser to be as small as possible .

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Riser Design

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  1. Riser Design • Riser is a waste part, as it will be separated from the casting body after the mold is destroyed and reused for casting (for expandable mold casting). • To minimize the waste of material, it is desirable for the volume of the riser to be as small as possible. • But we want to have a large TST of riser, which then contradicts the small volume idea, as TST of a riser increases while the volume increases. • Therefore, design of the riser should make a trade-off between the large TST and small volume. This trade-off can be achieved by the surface area, that is, to design a riser so that its surface area is as small as possible. • Further, a riser can be in the following forms: • Side riser (to the side of the mold cavity), top riser (above the mold cavity) • Open riser (exposed to the outside of the mold) or blind riser (enclosed in mold)

  2. Riser Design • For top riser, the area of the riser, which is connected with the casting or cavity, is not considered. • For open riser, the area of the riser needs to be multiplied by a coefficient, say C, so A’=C (A), where A’: the modified area, A: original area, and C>1.

  3. Example 1. Riser Design Given: • Casting geometry: rectangular plate: length = 7.5 cm, width=12.5 cm, thickness=2.0 cm • TST of the casting itself: 1.6 min. • The riser is a cylinder with diameter/height=1.0. Design a riser: such that TST of the riser= 2.0 min

  4. Determine V/A of plate • Given TST of plate, we determine Cm • We use the same Cm for riser design • Determine the volume of riser • Determine surface area of riser • As D/h=1, substitute D for h (1) Riser: • Side • Blind

  5. Substitute • Now we have got for the riser Vr/Ar, Cm, TSTr (2 min) and we get the following equation • In (2), Cm is found from Eq. (1). From (2), we can determine D Vr/Ar = D/6 (2)

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