The mold is cooled and the bottle is placed on a conveyor belt after being ejected from the mold. The stretching of the preform increases the barrier properties of the PET bottle. The preform is stretched as air is used to blow it into the shape of the mold. Next, the preform is conditioned and prepared for stretching. This injected plastic is then molded into a preform. IBM is used when manufacturing bottles with very tight neck tolerances.ĭuring the injection stretch blow molding (ISBM) process, the heated resin is injected into the machine using a long screw. Bottles with small blow-up ratios typically have small bodies and relatively small necks. This process is ideal for the production of HDPE, LDPE, and PP bottles with a small to medium blowup ratio. This injected plastic is molded into a preform, then air is used to blow the preform into the shape of the mold. Injection Blow Moldingĭuring the Injection Blow Molding (IBM) process, the heated resin is injected into the mold using a long screw. The EBM and CBM processes are also used when a bottle has multiple plastic layers (outside and inside) and when a transparent window stripe is needed to allow for determining the amount of product remaining in the bottle. This is ideal when the contents of the filled bottle require a thicker wall, or as a conscious effort to conserve raw materials by reducing the amount of plastic. This is done by controlling the amount of plastic in the parison. The EBM and CBM processes also allow the weight of the bottle to be adjusted. The CBM process can be used to manufacture bottles that are made with HDPE, LDPE, and PP resin, and can achieve very tight critical neck dimensions. Bottles with large blowup ratios typically have large bodies and relatively small necks. The blow-up ratio is the comparison between the diameter of the neck of the bottle and the diameter of the body of the bottle. We use CBM when producing bottles with medium to large blow-up ratios. This results in increased thread definition and precise bore tolerance. In CBM, the blow pin not only blows air into the parison so the plastic conforms to the shape of the bottle, but it also uses physical pressure to force the plastic into the neck area of the mold.

Compression Blow MoldingĬompression Blow Molding (CBM) is a specialized form of extrusion molding. We use the EBM process to manufacture large-size, High Density Polyethylene (HDPE), Low Density Polyethylene (LDPE), and Polypropylene (PP) bottles with large necks. The mold opens and the bottle is placed on a conveyor belt, the top (typically dome-shaped) is trimmed, leaving the finished bottle. The mold is then cooled, and the bottom of the parison is trimmed. The air pressure causes the parison to conform to the shape of the mold, including the threads in the neck portion of the mold. Once the mold is sealed, a blow pin is inserted into the neck area of the bottle and air is blown into it. A two-part mold closes on the parison from both sides. The parison is a vertical tube-like piece of plastic through which compressed air can pass. In the Extrusion Blow Molding (EBM) process, the heated resin is extruded to form a parison. No matter which manufacturing process is used, each one begins the same way – with pellets of plastic resin. How do the types of blow molding processes differ from one another? What criteria do we use to select the best process for your bottle? Read further or watch how the blow molding processes vary. Why? Because understanding how we manufacture our products will help you make more informed decisions about your plastic packaging. We believe it’s important for our customers to understand the primary differences between molding processes. Drug Plastics is committed to deliver perfect bottles each and every time. We use our knowledge acquired from over 50 years of bottle making to select the best molding process for every product we manufacture. In general, the size and geometry of the bottle, along with the type of plastic resin being used, determine which manufacturing process is best. Drug Plastics uses four distinct types of blow molding: Extrusion Blow Molding (EBM), Compression Blow Molding (CBM), Injection Blow Molding (IBM), and Injection Stretch Blow Molding (ISBM). Pressure forces the material into a mold cavity, which gives the object its hollow shape.

Blow molding is a process that uses heated liquid plastic to create hollow objects, like bottles or other packaging.

Soda bottle preform blanks