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The table shows the advantages and disadvantages of the different classes of pattern equipment used by sand casting process.
|
Advantages | Disadvantages | |
Wood Loose | Low cost to produce. Use to produce plastic patterns. Easily modified. | Not suitable for production batches unless converted into plastic before becoming worn. Tend to become inaccurate and to produce poor surface finish. | |
Hardwood | Inexpensive for small-batch production. Can be used as masters for plastic patterns. Fairly easily modified but expensive if multiple impressions involved. | Fair wearing properties. With care, will remain reasonably accurate over fairly long periods. Not suitable for high-volume production. | |
Plastic | Inexpensive to produce. Urethane technology provides good wearing properties and accuracy. Easily modified depending upon the materials used. Suitable for high-volume production patterns with the same dimensional tolerances as metal patterns. | Urethane technology has reduced many of the disadvantages of early plastic pattern materials. | |
Metal | Excellent wearing properties. High standard of accuracy and stability. Suitable for high-volume production and shell molding. CAD/CAM improvements are greatly reducing cost and lead time requirements. | Costly. Difficult to modify. Equipment is less adaptable for movement from one foundry to another. |