Plastic molding properties (continuation 4)

2024-05-17 15:30:29

Plastic molding properties

(continuation 4)

プラスチック成形特性 (続き4).jpg

(三) Specific volume and compression rate

Specific volume is the volume occupied by each gram of plastic (measured in cm3/g). The compression rate is the ratio of the volume or specific volume of plastic powder and plastic parts (its value is always greater than 1). They can both be used to determine the size of the die loading chamber. A large value requires a large volume of the charging chamber. It also means that there is a lot of air in the plastic powder, making it difficult to exhaust, resulting in a long molding cycle and low productivity. The opposite is true when the specific volume is small, and it is conducive to ingot pressing and suppression. The specific volumes of various plastics are detailed in Table 1-1. However, the specific volume value often has errors due to the particle size of the plastic and the unevenness of the particles.

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