ASTM D955-08 PDF

Mould shrinkage is defined as the difference between the dimensions of the mould and the moulded part. It is expressed either in millimetres per millimetre or, more commonly, as a percentage. Usually a general shrinkage value is quoted. Alternatively, two figures may be given — parallel in line of flow and perpendicular to the flow cross-flow. This is particularly important in the case of glass-filled materials, for example, as there can be a significant difference between the two figures.

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Mould shrinkage is defined as the difference between the dimensions of the mould and the moulded part. It is expressed either in millimetres per millimetre or, more commonly, as a percentage.

Usually a general shrinkage value is quoted. Alternatively, two figures may be given — parallel in line of flow and perpendicular to the flow cross-flow. This is particularly important in the case of glass-filled materials, for example, as there can be a significant difference between the two figures. Other factors affecting shrinkage include part design, mould design, mould temperature, injection pressure and cycle time.

Three types of specimen may be measured see below. Type A measures shrinkage in the flow direction only. The dimensions of the mould cavity are measured and then compared with the moulded specimen. The difference between the two as a proportion of the mould cavity size represents the shrinkage.

As testing is carried out on bars or discs the figures can only be a guide, so for mating parts or those with critical dimensions fine tuning may be required to the mould to achieve a suitable final part.

It must also be borne in mind that a plastic moulding will continue to shrink long after it has been ejected from the mould. For this reason mould shrinkage figures are based on dimension changes 24 hours after the part has been moulded. ASTM D ISO

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POLYMER SHRINKAGE

Undergraduate thesis, Institut Teknologi Sepuluh Nopember. Harga bahan baku plastik semakin hari semakin naik akibat meningkatnya kebutuhan akan produk plastik. Usaha untuk mencari material alternatif terus dilakukan, misalnya dengan mencampur material plastik dengan serat alam atau material organic lainnya, seperti sekam padi, serat sisal, dan lain sebagainya. Sejalan dengan proses pembuatan produk plastik dengan mesin injeksi, maka setiap material plastik yang digunakan harus diketahui sifat penyusutannya shrinkage , demikian pula dengan material alternatif plastik. Pada penelitian tugas akhir ini akan meneliti tentang nilai penyusutan dari material biokomposit sesuai dengan standar ASTM D Tahapan yang dilakukan dalam penelitian ini diawali dengan melakukan studi literature mempelajari tentang sifat mampu cetak khususnya shrinkage dan studi lapangan tentang cara kerja mesin. Kemudian membuat model 3D specimen untuk disimulasikan menggunakan moldflow.

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Historical Version s - view previous versions of standard. Work Item s - proposed revisions of this standard. More D Factors such as mold and melt temperature, fill times, and packing conditions are known to affect shrinkage significantly. Adherence to the specified mold design see 7.

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Standard Test Method of Measuring Shrinkage from Mold Dimensions of Thermoplastics

ASTM D Designation: D — 08 Standard Test Method of Measuring Shrinkage from Mold Dimensions of Thermoplastics1 This standard is issued under the xed designation D ; the number immediately following the designation indicates the year of original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A superscript epsilon indicates an editorial change since the last revision or reapproval. Differences in mold shrinkage may also be observed among the three specimen geometries described in this test method. The values given in parentheses are given for information only.

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