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Technology Technical introduction of HATACHI

Explanation on Blow Molding

Ordinary Blow Molding

Blow molding is a technology to heat thermoplastic resin up to melting temperature first, then extrude the melted resin through the die head, sandwich the extruded resin of tubular form (parison) and finally exert pressurized air into the inside of the sandwiched resin to obtain the shape of the mold.
Plastic vessels such as shampoo containers, kerosene containers etc. are almost formed by blow molding. Blow molding is a technology to literally blow resin by air and swell it to the shape of the mold.

Double Blow Molding

In ordinary blow molding, parison is sandwiched by the mold itself and formed by air blowing. In Double Blow Molding, however, there are double mold closing actions—namely, parison is first sandwiched by the frame installed on the outside of the mold just before the mold is closed, and then the mold is closed keeping the internal pressure of parison.
As molding is done under the condition that the internal pressure of parison is kept, more faithful copying of the mold and well-thickness -balanced products can be obtained than ordinary blow molding.
As for the shape of products, those of the right and left molds are almost symmetrical in ordinary blow molding, while those mainly unsymmetrical in Double Blow Molding. Products made by Double Blow Molding have duo-wall structure composed of inside and outside walls. Examples of products include musical instrument cases, tool cases, car bumpers etc.The mold closing process has double actions—closing of the frame and the mold and products have duo-wall structure, therefore, this technology is called Double Blow Molding.

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Large-size Blow Molding

Literally, blow molding of large-size products is so called.
Blow molding machines equipped with an extruder having screw/cylinder diameter of 90mm and more are classified as large-size machines.
So, blow molding by a machine of over 100mm is generally called large-size blow molding. Examples of products include truck bumpers, modular bath ceilings, solar tanks, construction machine covers etc.
We can make products of 2000mm length and 1300mm width by our existing machine.

Super Blow

Blow-molded products are mostly of hollow structure because they are formed by blowing parison by pressurized air.
Super Blow is a technology to simultaneously do two processes—filling foam beads in the hollow area and blow molding.
Products taken out of the mold have the layer of melted foam, bringing about excellent insulation and strength due to integrated structure.
Because of these features, this technology is used to make products which need heat-insulation, light weight and high strength and mainly used for modular bath ceilings, driftwood stopping floats etc.

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TP Process

Ordinary blow molding can't make well large-size products of duo-wall structure due to thinning or less ductility of the corner areas.
To solve this problem, the female mold of the forming molds is divided into 4 pieces which can move freely and the core mold is also so designed to move independently. Parison is sandwiched from upper, lower, right and left sides by these female molds and then the core mold is closed. By these mold actions, parison can reach the bottom, thus making deeply-drawn shape possible. This method which enables resin to run so smoothly that deeply-drawn shape can be molded is called TP Process.
Examples of products include event boxes, large-size planters, stools etc.

Details are here

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