Open-mold deposit

Back compression is a process based on compression molding (Chapter 14) of a melt strip deposited in an open mold. It describes the process during which a cover stock cutting is placed on a melt strip for simultaneous compression molding and lamination of parts. Melt strip deposition also includes fiber reinforced thermoplastic stock with subsequent compression molding of non-laminated structural parts. 

Both hand lay-up and spray-up processes essentially involve placing reinforcement and liquid resin onto the surface of an open mold. As the two names suggest, hand lay-up involves applying the resin and reinforcement (for example, glass fiber chopped-strand mats) by hand, while spray-up uses spray equipment to deposit resin and reinforcement (for example, chopped glass fibers) onto the mold. These relatively cheap techmques are often used to produce large, complicated, strong composite parts such as boat hulls. 

Rotational molding is used to form large shells of thermoplastic resin and chopped strands for such appHcations as agricultural tanks and fertilizer hoppers. The resin and chopped glass are placed in the metal mold that is then rotated in an oven where the thermoplastic resin melts and deposits the fiber on the metal surface. When cooled, the mold is opened and the part is removed. 

HoUow mol ding as the name implies is a molded product with a hoUow center such as Easter eggs, bunny rabbits, and Santa Claus. The molds used in hoUow mol ding are divided in two halves and connected by a hinge. Chocolate is deposited into one half of the mold. The mold is then closed and rotated so that the Uquid chocolate completely coats the inside surface of the mold. After cooling the molds are opened and the piece removed. 

While the manifolds were fabricated by a plain molding process, the microchannels substrate fabrication was quite complicated and was achieved by a multistage process. The following main stages were used in the process (1) double side oxidation of a 525 pm (1 0 0) silicon substrate to 1,000 A, (2) single side 1,200 A silicon nitride deposition, (3) silicon nitride channels template opening by reactive... 

The mold is prepared as for hand lay-up but the resin and reinforcement are applied either by spray gun, which can be operated manually or by robot. This gives a more reproducible process, with greater control over the amount of each material that is deposited, opening the way to complete automation. The process has been a popular system... 

The purpose of the injection unit is to heat and melt the polymer, inject the melt into the cavity, and apply pressure during the cooling phase. The most common type of injection molding machine is the reciprocating screw. In this type of machine, the screw rotates to plasticize the polymer, moving backward to deposit a volume of polymer melt ahead of the screw (shot). Once the correct shot size has been built, the screw then moves forward to inject the melt into the mold. Injection molding is a discontinuous process, and the clamping unit allows for the mold to open and close for part removal and to provide pressure as the cavity is filled. This is depicted in Fig. 1.19. 

Rotational molding utilizes a closed female mold. The mold is opened and filled with a predetermined weight of powder or liquid. It is then swung into the oven section of the equipment and rotated around its primary and secondaiy axes. The oven heats the mold which, in turn, heats the powder. As the powder melts, it deposits imiformly on the interior walls of the mold. When all the material is deposited on... 

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