Injection blow molding machines

Use is made of screw tip valves, popularly called non-return valve, ball check valve, or sliding ring valve. They are used in reciprocating injection and injection blow molding machines (IMM and IBMM) to control the melt flow in one direction (Chapter 4). There is also the smearhead for IMM, IBMM, and extruder. Back flow will not occur... 

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.

Fig. 1. Three-station injection blow-molding machine utilizing a vertical screw produced by Jomar, Pleasantville, N.J., U.S.A.

Fig. 3. A typical three-station injection blow-molding machine. Courtesy of Rainville Operation, Hoover Universal, Inc.

FIGURE 1.160 Injection blow molding machine with injection, blow and ejection station (Upper left) work table, turning horizontally in the parting plane (Upper right) injection mold with parted multi-cavity mold (Lower left) blow unit... 

There are both three- and four-station injection blow molding machines in the industry today. Wheaton Industries, which is one of the largest injection blow molders in the world, pioneered the four-station design, primarily for safety. However, with the movement to PET on the injection blow molding machines the fourth station has become a necessity to allow for the core rods to be conditioned through the use of an air chamber. The core rods are not temperature controlled, but are allowed to have their bodies or shanks, to cycle within a specified temperature window. 

Normally, the injection blow molding machines use the horizontal rotary transfer table (Gussoni Method) as Wheaton, Jomar, Bekum, Fischer, and Johnson Controls. Battenfeld Fischer also produced a vertical rotary... 

All the injection blow molding machines sold today use a horizontal recriposcrew plastifier for injection molding the preform except Jomar, though Jomar has now offered a horizontal recriposcrew, a deviation from their vertical screw design. 

Most injection blow molding machines are designed to accept tooling from others as Rainville s tooling will fit into a Wheaton machine and vice versa. The modiflcations are relatively easy and inexpensive to fit tooling from one make machine to another if no additional cavities are required. 

Fig. 14.18 Schematic of the three-position injection blow-molding rotary machine. The third position is easily accessible for removing the blow-molded article. [Reprinted by permission from Modem Plastics Encyclopedia, Vol. 53, McGraw-Hill, New York, 1976-1977.]...

Figure 8-4. Schematic of three-station blow-molding machine (McCrum, Buckley, and Bucknall 1997, courtesy of Oxford University Press). Station 1 injection molding of parison station 2 blow molding of bottle station 3 ejection of bottle.

It is estimated that in USA there are about 17,000 extruders, 70,000 injection molding machines, and 6,000 blow molding machines producing about one-third of the world s plastic products. For the 80,000 IMMs in USA the usual report shows that 30% are under five years old, at least 35% are five to ten years old, and the rest are more than ten years old. 

The term dispersion refers to how well the pigments are wetted out in the plastic matrix (see below), whereas distribution refers to the uniformity of color in the part. Finally, in referring to the parts fabrication process, the term molder is used below to represent any the following pieces of equipment injection molding machine, injection or extrusion blow molding machine, or rotational molding machine. 

Future advances for the injection blow molding process are in tooling for bottles with special tabs, the use of process control to profile the melt injection pressure, and the use of microprocessor control when the volume of machines on the market makes it economical. 

More recent is the University of Twente mixing ring (or TMR). This device is made olf three parts smooth wall barrel extension, a torpedo with semi-spherical indentations (similar to these in CTM) and a perforated sleeve that goes between them. The sleeve provides shallow indentations. It slowly rotates between the torpedo and the barrel by the virtue of a drag flow. The flow in TMR is both dispersive and distributive. The advantage of TMR is its suitability to improve mixing in injection or blow molding machines [Housz, 1989]. 

In nearly all applications of piastics in packaging, the first step is to convert the soiid piastic, usuaiiy in peiiet form, into a meit. This meit can then be shaped using heat and pressure into a usefui form. The equipment used to do this is an extruder. An extruder is used for him and sheet, and is part of a blow molder for bottles. An extruder is also part of an injection molding machine for injection molded or injection blow molded packaging. The extruders used in all of these applications work in a similar manner, but they deliver the melt to the shaping operation differently. We will explore these differences as we proceed. 

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. 

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