Injection Blow Molding Injection is part injection molding and part blow molding. Injection Blow Molding is generally suitable for smaller containers and absolutely no handles ware. Injection blow molding is often used for containers that have close tolerance threaded necks, wide mouth openings; solid handles, and highly styled shapes. Injection blown containers usually have a set gram weight which cannot be changed unless a whole new set of blow stems are built. Generally injection blow molded container's material is distributed evenly throughout, and generally do not need any trimming or reaming. The air is injected into the plastic at a rate between 75 to 150 PSI. PP, HDPE, LDPE, PVC are some of the more common IBM bottle resins.
Stages of the IBM process
Injection molding can be broken down into three stages.
- The FIRST STAGE is where the melted plastic is injected into a split steel mold cavity from the screw extruder.
- The mold produces a preform parison which resembles a test tube with a screw finish on the top.
- In the SECOND STAGE, the preform is then transferred on a core rod to the second part of the injection blow molding stage.
- The preform is then placed inside another cold and usually aluminum blow mold cavity.
- Air is then injected through the core rod till the preform takes the shape of the cavity.
- In the final, THIRD STAGE, while still on the core rod, the container is then transferred to a desired location for the third stage, where it is ejected from the machine.
Advantages of IBM
Bottles produced via this method have a tight tolerance when it comes to neck finish dimensions, wall thickness, and gram weight. It is commonly used to produce pharmaceutical and healthcare bottles such as wide mouth packers. IBM machines often use multi cavity molds across all three stations that yield a higher output.
Different from EBM (Extrusion Blow Molding), it yields virtually no scraps and given it’s excellent neck finish control, it can be produced with a controlled finish ID to accommodate snap-in orifice reducer and dropper plugs.
Things to know
IBM process generally has a longer tooling development timeline and higher mold equipment costs. Therefore it is generally used to produce high volumes of bottles. These bottles can fairly easily be identified via the small injection point at the base of the bottle.