Molding Systems

Although considered by some to be a batch process, injection molding is really a semicontinuous process. Further, it is also a cyclic process in which plastic granules are heated until melted or thermally softened, forced into a mold and then cooled to a desired shape. 

There are four principal types of injection molding that are used to heat the plastic and then force the molten or thermally softened polymer into the mold. These include  

The single-stage plunger (Fig. 8-3) is the oldest of all of the systems in use. It is activated by hydraulic pressure (up to 2.1 X lO kPa). A heated torpedo is used to spread the plastic and to assist in softening or melting it. The plunger forces the resultant softened or molten plastic into the mold. 

The two-stage plunger-plunger (Fig. 8-4) system uses one device to create 

The reciprocating screw unit (Fig. 8-6) is fed solid plastic through a hopper. When the mold is closed off, the plastic is melted, and a considerable back pressure is generated. This back pressure moves the screw to the rear and leaves a reservoir of molten plastic ahead of the screw. 

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The dimensional tolerances with the more conventional single-mold system are generally 0.6% ( 0.35% for close tolerances). With female molds 0.5% ( 0.3% close) with male molds under 3 ft., 0.8% ( 0.4% close) and with male molds over 3 ft., 30% ( 10% close) for wall thicknesses. 

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. 

Gordon, D., Aluminum Molds Go the Distance, Molding Systems, Mar. 1999. 

Figure 7.81 Schematic diagram of rotating mold system used in continuous extrusion blow molding. Reprinted, by permission, from A. B. Strong, Plastics Materials and Processing, 2nd ed., p. 489. Copyright 2000 by Prentice Hall, Inc.

The ring-opening metathesis polymerization of dicyclopentadiene was monitored by ultrasonic spectroscopy.16 The thermoset poly(dicyclopentadiene) is formed by ringopening and cross-linking in a reaction injection molding system. A reaction cell with a plastic window was constructed for use with pulse echo ultrasonic spectroscopy. Realtime measurements of density, longitudinal velocity, acoustic modulus and attenuation were monitored. Reaction kinetics were successfully determined and monitored using this technique. 

Schematic diagram of an eight cavity mold system with various runner lengths and...

Machine process controls coordinate individual functions of the clamp, injection unit, ejector mechanism, and mold systems and accessories such as core pulls and unscrewing dies for threaded parts. The more advanced controls employ a feedback system (closed loop) to provide much tighter control over actual parameters vs. setpoints. High-level controls are capable of communicating with auxiliary equipment such as chillers, hopper loaders, mold temperature controllers, robots, etc., and displaying all machine parameters and conditions (Chapter 3)... 

Figure S.7 Introduction to a continuous extruded blow molding system with its accumulator die head...

There is double-axis rotation, carousel, shutde, clamshell, rock-and-roll machines, and so on. These designs are similar to other molding systems whereby multiple molds can be used to speed up or even simplify production. Double-axis RM uses two platforms to hold molds. The carousel types can have three to six arms for mounting molds. 

Three station injection blow molding system 296... 

Looije PA Sabapathy PA Di Simone J Keir W S Husky Injection Molding Systems Ltd. 

The relationships obtained (7-9) linking up the temperatures and the time that the material is present in the various zones of the plastification and molding systems constitute a basis for a further optimization of the temperature-time regimes of pressure casting of reactoplasts, including granulated cast aminoplasts. 

Self-Releasing Urethane Molding Systems Productivity Study... 

This review identifies the primary reason for utilizing self-releasing urethane molding systems increased productivity. In achieving this goal, however, the practical issues of various performance features, which may be critical to overall results, must be recognized, understood, and dealt with. 

Profiles of Temperature and State of Cure Developed Within Rubber in Injection Molding Systems... 

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