Molding process steps

Fig. 14.20 Schematic representation of the injection stretch blow-molding process. Step (1) producing preforms may be carried out in different location from the stretch blow molding process. [Reprinted by permission from Schmidt et al., Experimental Study and Numerical Simulation of the Injection Stretch/Blow Molding Process, Polym. Eng. Sci., 38, 1399 (1998).]...

This new injection molding process step, compared to the standard IM method first developed about 15 years ago (see Sects. 3.1 and 5.2.4 in Chapter Processing (Primary Forming) of Plastics into Structural Components ), involves opportunities and risks as illustrated in Table 12, whereby the opportunities predominate by a long shot and the risks have now been practically nullified by a new processing method. 

Fig. 12. HDPE blow molding processing steps (a) extrusion of parison, mold is open (b) mold is closed (c) air is blown into parison and (d) mold is opened for removal of article.

Figure 4. Gelation injection molding processing steps [7].

One channel is made by KOH etching (in the framework of the above-mentioned technology steps), the other by a molding process using an PDMS mold and an epoxy cast. 

The plasticator on an injection-molding machine is a specialized plasticating single-screw extruder. The plasticator has two main differences there is a nonreturn valve on the tip of the screw, and the screw retracts as molten material accumulates between the nonreturn valve and the end of the barrel. Pressure is maintained on the accumulated material by a constant force applied to the shank of the screw via the drive system. This force is typically measured as a pressure applied to the shank and is referred to as the back pressure. During the injection step of the process, the screw is forced forward, the nonreturn valve closes, and the material is injected into the mold. Additional information on the injection-molding process can be obtained elsewhere [Ij. 

Blow-molding processes consists of five main operations plastication of the resin, formation of the parison, inflation of the parison, solidification of the part, and removal of the part from the tooling. The best process economics will occur with a part optimized for weight and a minimum cycle time. In order to have a minimum cycle time, the cooling operation must be the rate-limiting step. For the case study... 

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