Preform molding

Husky is a global supplier of injection molding systems to the plastics industry. Husky designs and manufactures injection molding machines—from 60 to 8000 tonnes, robots, hot runners for a variety of applications, molds for PET preforms, and complete preform molding systems. Customers use Husky s equipment to manufacture a wide range of products in the packaging, automotive and technical industries. The company serves customers in over 100 countries from more than 40 service and sales offices around the world. 

The major difference between injection and extrusion blow molding is the way the soft hollow tube (called a preform or parison) is made. In injection blow molding, two different molds are used. One mold forms the preform and the other mold is used in the actual blow-molding operation to give the final shaped article. In the molding process, the softened material preform, from the preform mold, is introduced into the blowing mold and blow-molded to... 

We have chosen to divide the rest of this chapter into three sections on the important topics of preforming, mold filling, and in-mold cure, followed by a section with a brief review of mold design and related topics. 

Resin Transfer Molding (RTM). Reinforcing fibers are distributed uniformly in the mold and the mold is closed. Liquid resin is injected into the mold until the excess comes out of the vents. The mold is pressed and heated, similarly to preform molding, until cure is complete. 

Toensmeier, P. A., Kortec Readies 144 Cavity Coex PET Preform Mold, MP, June 2003. 

The fabrication of microelectromechanical systems (MEMS), e.g. actuators and sensors, is also one of the promising applications for nickel films. Nickel is currently electroplated into preform molds. One typical process is the LIGA process, where pure or alloyed nickel films are... 

Insulation of industrial plants with loose wool, sheets tmd rolls, as well its preformed molded components... 

Injection blow molded bottles are generally blown on the same machine as the one that makes the preforms. It is a multistation machine, where the first station does the injection molding, the second station blows the bottle, and the third station ejects the finished bottle from the machine. The process is often arranged on a horizontal table, as shown in Fig. 12.10. Multiple cavity preform molds and bottle molds can be used in the process. However, the cavitation (the number of cavities) is limited by the size of the rotary table. 

Figure 12.14 Husky PET preform molding machine, view 1, reprinted by permission of Husky...

Two techniques are used for producing the multilayer injection molded preforms. The technology used for the Heinz PET/EVOH ketchup bottle involves simultaneous injection of two or more resins into the mold cavity in such a way that they remain in distinct layers. The second process involves a multiple set of preform molds, with a single resin injected in each step. 

Hand lay-up, spraying Filament winding SMC BMC Preform molding... 

Different types of microprocessor-based modules control BM machines and melt parameters, ranging from single to multiple functions. The modules interact at high speeds, coordinating process variables such as heat, timing, parison or preform molding speed and pressure, melt wall thickness, and so on. (See Chapters 2 and 3 on controlling injection and extrusion machines.)... 

Injection molding Hand lay-up Spray-up Compression molding Preform molding Filament winding Pultrusion Resin transfer molding Reinforced reaction injection molding ... 

Figure 1.4 Three Station Injection Blow Molding Machine [Miller, 1983]. The parison is injection molded on a core pin (instead of as a tube in free air, as with extrusion blow molding) at the preform mold station (1). The parison and neck finish of the container are formed there. The parison is then transferred on the core pin to the blow mold station (2) where air is introduced through the core pin to blow the parison into the shape of the blow mold. The blow container is then transferred to the stripper station (3) for removal.

Preform molding has the highest strength of these three systems. It is best for uniform wall designs requiring deep draws. SMC is better able to handle ribs, bosses, and thinner walls. LPMC is a variety of SMC which is modified to require less molding pressure, enabling it to... 

With respect to Fig. 8.32, the nominal wall thickness (W) can vary from 0.045 to 0.250 in for preform-molded parts, 0.080 to 0.500 in for SMC-molded parts, and 0.060 to 1.000 in for BMC parts. The process can handle variations of 100% for preform molded parts, even more for BMC and SMC (300%) however, the transition between wall thicknesses must be gradual. Wall thickness variations of 0.010 in can be anticipated. In general, these processes can handle tolerances nearly as tight as those for the short-fiber processes. 

Ribs (B) and metal inserts (E, H) are not recommended for preforms, but they can be used with the other versions. The minimum inside radius (IR) is 0.125 in for preform-molded parts and 0.062 in for SMC-and BMC-molded parts. Long-fiber compression-molded parts can be trimmed in the mold. For Class A finishes in SMC parts, the inside radius at the base of a rib should be 0.020 in otherwise it should not be less than 0.060 in. The thickness at the base of the rib (B) can be equal to the nominal wall thickness (W), however, it must not exceed 0.75W under Class A surfaces. The height of the rib (C) should be 2 to 3 times the nominal wall thickness (W) and the draft should not be less than 1° per side except for ribs imder Class A surfaces (which can handle the cost premium) where it can go down to 0.5° per side. These same rib design rules apply to boss wall thicknesses for these parts. In-mold coating can be used for high-class finishes. 

In injection blow molding, the parison is injected into a preform cavity and around a core pin in the exact quantity required to form a container. The preform mold is kept at a precisely controlled temperature, which is just a little cooler than the melt temperature. After injection, the mold opens, and the core pin and the still warm preform are rotated 120°. A blow mold then closes over the preform, and air is injected through the core pin. After the container is blown, it is rapidly cooled by contact with the walls of the blow mold, which are kept at around 102-122°C by cold air or fluid circulating through the mold passageway. The mold then opens, a second 120° rotation occurs, and the part is stripped from the core pin. Then a third 120° rotation of the transfer head returns the core pin to the preform injection mold, and the cycle is repeated. 

Injection blow-molding requires two molds one for molding the preform or pari-son, and the other for molding the bottle. The preform mold consists of the preform cavity, injection nozzle, neck-ring insert, and core-rod assembly. The blow mold consists of the bottle cavity, neck-ring insert, and bottom-plug insert (see Figs. 6-10). 

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