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Method for blow moulding of unround hollow articles with uniform wall thickness distribution with the use of under- and over-pressure between the preform and the cavity wall
Method for blow moulding of unround hollow articles with uniform wall thickness distribution with the use of under- and over-pressure between the preform and the cavity wall
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机译：利用预型件和型腔壁之间的负压和负压吹塑壁厚分布均匀的非圆形空心制品的方法
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摘要
In addition to a fluid or gas for inflating a preform in a tool cavity a second medium is introduced and/or removed from two or more areas between preform and cavity wall. Each partial flow is controlled so that excess pressure slows the approach of a preform to the wall in areas(I,II) where preform and wall make first contact and vacuum is created in areas(III,IV) where the preform and wall are last to make contact to accelerate preform movement towards the wall. A balance between preform approach and freezing stages is achieved which minimizes wall thickness variation around the periphery. During preform inflation extraction of the second medium from the area between tool wall and preform is controlled. Air, which may be heated, is used for both preform inflation and control of preform expansion. Air enters the tool cavity via bores, slits, inserts with bores or slits and/or inserts of permeable sintered material. Volumetric flows of the second medium are controlled in relation to the thermoplastic material, inflation pressure, molding size and shape and/or wall thickness.
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