Advantages and Disadvantages
One of the greatest advantages of this process is that it can be completely automated for mass production. The high productivity, low labor costs, good surface finishes, and precision of the process can more than pay for itself if it reduces machining costs. There are also few problems due to gases, because of the absence of moisture in the shell, and the little gas that is still present easily escapes through the thin shell. When the metal is poured some of the resin binder burns out on the surface of the shell, which makes shaking out easy.
One disadvantage is that the gating system must be part of the pattern because the entire mold is formed from the pattern, which can be expensive. Another is the resin for the sand is expensive, however not much is required because only a shell is being formed. Property Name Shell Mold Casting Sand Casting Shapes Thin-walled: Complex, Solid: Cylindrical, Solid: Cubic, Solid: Complex (Flat, Thin-walled: Cylindrical, Thin-walled: Cubic) Thin-walled: Complex, Solid: Cylindrical, Solid: Cubic, Solid: Complex (Flat, Thin-walled: Cylindrical, Thin-walled: Cubic) Part size Weight: 0.5 oz - 220 lb Weight: 1 oz - 450 ton Materials Metals, Alloy Steel, Carbon Steel, Cast Iron, Stainless Steel, Aluminum, Copper, Nickel Metals, Alloy Steel, Carbon Steel, Cast Iron, Stainless Steel, Aluminum, Copper, Magnesium, Nickel (Lead, Tin, Titanium, Zinc) Surface finish - Ra (μin) 50 - 300 (32 - 500) 300 - 600 (125 - 2000) Tolerance (in.) ± 0.015 (± 0.006) ± 0.03 (± 0.015) Max wall thickness 0.06 - 2.0 0.125 - 5 (0.09 - 40) Quantity 1000 - 1000000 (100 - 1000000) 1 - 1000 (1 - 1000000) Lead time Weeks (Days) Days (Hours)
Advantages Can form complex shapes and fine details, Very good surface finish, High production rate, Low labor cost, Low tooling cost, Little scrap generated Can produce very large parts, Can form complex shapes, Many material options, Low tooling and equipment cost, Scrap can be recycled, Short lead time possible
Disadvantages High equipment cost Poor material strength, High porosity possible, Poor surface finish and tolerance, Secondary machining often required, Low production rate, High labor cost Applications Cylinder heads, connecting rods Engine blocks and manifolds, machine bases, gears, pulleys
Read more about this topic: Shell Molding
Famous quotes containing the word advantages:
“... there are no chains so galling as the chains of ignorance—no fetters so binding as those that bind the soul, and exclude it from the vast field of useful and scientific knowledge. O, had I received the advantages of early education, my ideas would, ere now, have expanded far and wide; but, alas! I possess nothing but moral capability—no teachings but the teachings of the Holy Spirit.”
—Maria Stewart (1803–1879)