Last Updated on June 8, 2000
By Tim Trump
castings, machining, forging,castings, machining, forging,castings, machining, forging,castings, machining, forging,castings, machining, forging,castings, machining, forging,castings, machining, forging,castings, machining, forging,castings, machining, forging,castings, machining, forging,
| CASTING PROCESS | DESCRIPTION | METALS | SIZE RANGE | TOLERANCES | TOOLING COST | RELATIVE COST IN QUANTITY | RELATIVE COST FOR SMALL QTY. | SURFACE FINISH | MIN. DRAFT REQ. | NORMAL MIN. SECTION THICKNESS | EASE OF CASTING COMPLEX DESIGN | EASE OF CHANGING DESIGN IN PROD. | STATUS | |
| AVERAGE | RANGE | |||||||||||||
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INVESTMENT CASTING |
Metal mold makes wax or plastic replica. These are sprued, then surrounded with investment material and baked out. Metal is poured in resultant cavity. |
Most all Castable Metals | Fraction of an ounce to 100 pounds | +/-.005" up to 3" +/-.002" there after | $2500 | $500 - $20,000 | Highest | Medium | 60-120 RMScastings, machining, forging,castings, machining, forging,castings, machining, forging,castings, machining, forging,castings, machining, forging,castings, machining, forging,castings, machining, forging,castings, machining, forging,castings, machining, forging,castings, machining, forging,castings, machining, forging, | Nonecastings, machining, forging,castings, machining, forging,castings, machining, forging,castings, machining, forging,castings, machining, forging,castings, machining, forging,castings, machining, forging,castings, machining, forging,castings, machining, forging,castings, machining, forging,castings, machining, forging, | Aluminum Alloy:
.030" Beryllium Copper: .030" Ductile Iron:
.060" Carbon Steel: .090" |
Bestcastings, machining, forging,castings, machining, forging,castings, machining, forging,castings, machining, forging,castings, machining, forging,castings, machining, forging,castings, machining, forging,castings, machining, forging,castings, machining, forging,castings, machining, forging,castings, machining, forging, | Faircastings, machining, castings, machining, forging,forging,castings, machining, forging,castings, machining, forging,castings, machining, forging,castings, machining, forging,castings, machining, forging,castings, machining, forging,castings, machining, forging,castings, machining, forging,castings, machining, forging,castings, machining, forging, | Used for precision castings, particularly in gas turbine engines. A specialized processs usually performed in foundrys not used for other processes. |
| DIE CASTING | Molten metal is injected under pressure into hardened steel dies. | Aluminum, Zinc, Magnesium, and limited Copper Base | Not normally over 3 feet sq. Some foundrys capable of larger sizes. | .0015"/in. Not less than .002" on any one dimension. Additional .010" on dimensions affected by parting line. | $25,000 | $5,000 - $150,000 | Lowest | Highest | 20-90 RMS | Aluminum: 1 to 3 degrees Zinc & Mag: 1/2 to 2 degrees | Aluminum: .050" Small parts .080" Med parts Zinc & Mag.: .025" Small parts .040" Med. Parts | Good | Poorest | Very widely used for high production of aluminum and zinc castings. An inexpensive way of obtaining precision parts |
| PERMANENT MOLD | Molten metal is gravity poured into cast iron molds, coated with ceramic mold wash. Cores can be metal, sand, shell or other. | Primarily Aluminum with some Copper Base and Cast Iron. | Limitation mainly foundry capabilities. Aluminum: Usually 1/2 lb. To 100 lbs. | Aluminum: +/-.015 to 1" add .002" for ea. additional inch. If across parting line add +/- .010" (Small Casting) to +/-.030" (Large Casting) | $8,000 | $1,500 - $75,000 | Low | High | Aluminum: 125-200 RMS Iron: 200-420 RMS Copper Base: 175 - 225 RMS | Aluminum: 2 to 4 deg. Iron: 3 to 5 Copper Base: 3 to 5 | Aluminum: .100" to .150" Iron: .187" to .250" Copper Base: .100" to .150" | Fair | Poor | Used for moderate quantities of semi-precision castings. Is normally less expensive than sand casting for 100's part or a few 1000 parts. Limited applicability for ferrous metals. |
| V PROCESS | Cope and Drag Method. Softened plastic is drawn to pattern. Sand is backfilled. | Most all Castable Metals | All sizes | +/-.020" up to 6" then +.002" per inch. Add .020" per inch across parting line. | $5,000 | $3,000 - $20,000 | Medium | High | 125-150 RMS | None | 0.090" to 0.125" | Good | Fair | Unlimited pattern life. Used for medium to med high volumes. |
| SHELL MOLD | Resin coated sand is poured onto hot metal patterns, curing into bonded sand mold halves. These are removed from pattern, assembled with or without cores, and metal is poured into the resultant cavitites | Most all Castable Metals | Normal maximum 550 sq. in. usable mold area | Ferrous: +/-.008" per in. up to 3" Add .003" per in. over 3" Non-Ferrous: under 1" = +/-.004" 1"-3" = +/-.010" 3"-6" = +/-.013" 6"-12" = +/-.016" 12"-20"= +/-.020" Add .005"-.010" across parting lines | 5000 | $1500 -$25,000 | Medium | Medium | Iron: 200-350 RMS Copper Base: 150-200 RMS Aluminum: 75-125 | Outside: 0 to 1-1/2 deg Inside: 0 to 2 deg | Non-Ferrous: .100" Ferrous: .125" | Good | Fair | Used for production of fairly small parts for which closer tolerances are required than are obtainable from sand castings. Widely used for cores. |
| SAND CASTINGS | Cope and Drag Method - Tempered sand is packed onto wood or metal pattern halves; removed from pattern, assembled with or without cores and metal is poured into resultant cavities. Various materials can be used. | Most Castable Metals | Limitation mainly foundry capabilities. All sizes. | 0-3" = 1/32" 3"-6" = 3/64" +6" = +1/16" Across parting line add .020" to small castings .090" to large castings | $2,000 | $50 - $15,000 | Low | Lowest | Aluminum: 175-350 RMS Copper Base: 300-560 Ferrous: 420-900 RMS | 1 to 5 | Non-Ferrous: .125"-.250" Ferrous: 250"-.375" | Fair to Good | Best | Most widely used process for ferrous metals for both small and large production runs. Various binder systems available. |
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Last Updated on June 8, 2000
By
Tim Trump