CASTING PROCESS

DESCRIPTION

METALS

SIZE RANGE

TOLERANCES

AVERAGE TOOLING COST

RELATIVE COST FOR HIGH QTY

RELATIVE COST FOR LOW QTY

SURFACE FINISH

MINIMUM DRAFT REQUIRED

MINIMUM SECTION THICKNESS

EASE OF CASTING COMPLEX DESIGNS

EASE OF CHANGING DESIGN

COMMENTS

GREEN SAND
Process that mixes raw sand, clay and water, which is then compacted around a pattern to create a mold.Most common type of molding, suitable for anyproduction volume, and typically a low-cost option.

Most Castable Metals

All sizes per foundry capabilities

0-3" = 0.03" per in. + 0.005" per in. for each additional in. Across parting line add 0.020" to small castings,0.090" to large castings

Low

Low

Low

Ferrous: 420-900 RMS Aluminum: 175-350 RMS Copper Base: 300-560 RMS

1-5 degrees

Ferrous: 0.250-0.375" Non-Ferrous: 0.125-0.250"

Fair to Good

Best

Most widely used casting process for both small and large production runs.

NO BAKE / AIRSET


Molding method utilizing raw sand combined with resins and binder to create a hard mold capable of improved surface finishes. Excellent for lower-volume parts where superior dimensional stability is required.

Most Castable Metals

All sizes per foundry capabilities

0-3" = 0.03" per in. + 0.005" per in. for each additional in. Across parting line add 0.020" to small castings, 0.090" to large castings

Low

Low

Low

Ferrous: 420-900 RMS Aluminum: 175-350 RMS Copper Base: 300-560 RMS

3-5 degrees

Ferrous: 0.250-0.375" Non-Ferrous: 0.125-0.250"

Fair to Good

Best

Widely used casting process for both small and large production runs.

SHELL

Resin-coated sand, typically of a smaller grain size than green sand, which is applied to a heated pattern that activates the resin to create a hard-shell mold. Exceptional surface finishes can be achieved with reduced machine stock and/or draft.

Most Castable Metals

Typical max mold area = 3000 in2

Ferrous: +/-0.008" per in. up to 3" add 0.003" per in. over 3" Non-Ferrous: Add 0.005-0.010" per in. across parting lines, under 1" = +/-0.004" 1-3" = +/-0.010" 3-6" = +/-0.013"6-12" = +/-0.016" 12-20" = +/-0.020"

Medium

Medium

Medium

Ferrous: 200-350 RMS Aluminum: 75-150 RMS Copper Base: 150-200 RMS

0.5-2 degrees

Ferrous: 0.125" Non-Ferrous: 0.080"

Good

Fair

Used for production of fairly small parts for which closer tolerances and improved surface finishes are required than are obtainable from sand castings. Widely used in core production.

INVESTMENT

Casting process in which wax replicas are coated with a slurry mix of ceramic refractory and sand, allowed to dry, and then heated to extract the wax, leaving behind a near-net-shape cavity. Capable of creating shapes that are not possible by any other molding method, particularly for small or intricate components. Widely used to eliminate additional machining expense.

Most Castable Metals

0.1 to 100 lbs

+/-0.005" per in. up to 3" add 0.002" per in. over 3"

Medium

High

Medium

60-120 RMS

0-1 degrees

Carbon Steel: 0.090" Stainless Steel: 0.125" Aluminum: 0.030" Copper Base: 0.030"

Best

Fair

Used for precision castings, particularly for complex designs.

LOST FOAM

Can be utilized in two different methods; The first method is similar to investment, in which a polystyrene replica is coated with ceramic refractory and then molded in sand. The second method consists of foam patterns that are molded into a media similar to no bake or airset. In either method, molten metal is poured directly into the sand mold and evaporates the foam during the casting process, creating a part with no draft or parting lines.

Most Castable Metals

Up to several hundred pounds

0-3" = 0.03" per in. + 0.005" per in. for each additional in. Across parting line add 0.020" to small castings, 0.090" to large castings

Low

High

Low

Per type of foam used

None

Ferrous: 0.250-0.375" Non-Ferrous: 0.125-0.250"

Good

Good

Widely used for prototypes and low usage parts. In some cases patterns can be used more than once.

PERMANENT MOLD

Reusable metal tooling that can be used to create repeatable dimensional accuracy, typically used for decorative or ornamental products made from nonferrous materials.

Aluminum & Copper Base

All sizes per foundry capabilities; Aluminum = 0.5 to 100 lbs.

Aluminum: +/-0.015" per in. up to 1" add 0.002" per in. over 1" Across parting line add0.010" to small castings,0.030" to large castings

Medium

Medium

High

Aluminum: 125-200 RMS Copper Base: 175-225 RMS

Ferrous: 3-5 degrees Aluminum: 2-4 degrees Copper Base: 3-5 degrees

Ferrous: 0.187-0.250" Aluminum: 0.100-0.150" Copper Base: 0.100-0.150"

Fair

Poor

Used for moderate quantities of semiprecision castings. Normally less expensive than sand casting for100's - 1000's of parts. Limited applicability for ferrous metals.

DIE CAST

Method in which molten metal is forced into a metal die under pressure. This process is suitable for repeatability of medium- to high-volume, intricate or close-tolerance parts.

Aluminum, Zinc, Magnesium, & Copper Base

Typical max mold area = 3 ft2

0.0015" per in. Not less than 0.002" on any one dimension. Across parting line add 0.010"

High

Low

High

20-90 RMS

Aluminum: 1-3 degrees Zinc & Mag: 0.5-2 degrees

Aluminum: 0.050" Small 0.080" Med Zinc & Mag.: 0.025" Small 0.040" Med

Good

Poorest

Very widely used for high production of aluminum and zinc castings. An inexpensive way of obtaining precision parts.

CENTRIFUGAL

Process utilizing permanent tooling that is rotated horizontally or vertically while molten metal is introduced, typically used to manufacture pipe or other cylindrical products.

Most Castable Metals

OD 2 to 50 in; Length & wall thickness per foundry capabilities

OD = 0.1" Small Dia ID = 0.03-0.06"

None

Low

Medium

250-500 RMS

None

Per foundry capabilities

Not Practical

Good

Used for round tubular or cylindrical castings. ID will likely require machining due to impurities. Excellent casting soundness.

V-PROCESS

Dry sand molding method that uses a vacuum to hold a membrane on the surface of the pattern, which is then backfilled with sand. Advantages are exceptional surface finish and tighter dimensional control than most conventional sand casting processes.

Most Castable Metals

All sizes per foundry capabilities

+/-0.010" per in. up to 1" add 0.002" per in. over 1" Across parting line add 0.020" max

Medium

Medium

High

125-250 RMS

None

0.090-0.125"

Good

Good

Unlimited pattern life. Used for medium to high volumes.