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Blow Machines

The first four steps take place in sequence; the fifth is performed while the other 4 steps are cycling. Exceptions occur when a number of pieces are produced on the same blow machine, simultaneously, then the four steps may overlap. Most of the cycle time is taken up by the blowing and cooling step. Therefore (step 3) blowing and cooling control the blow machine cycle. The speed of the blow machine that melts the resin and makes the parison must be configured to conform to the blowing/cooling time.
Hot runner adapter plates enable an blow machine to be used for material analyses and material development for which previously different injection molding machines were required. Additionally the quick changing time of an hot runner adapter plate allows the blow machine to be used within a great variety of research projects. As with all polymer processing equipment, blow machine employs powerful and potentially dangerous electrical, hydraulic, pneumatic, thermal and mechanical systems. Blending can be done in a batch process via tumbling, or on-line at the blow machine with automatic dosing units equipped with a mixing chamber. Either is sufficient to blend color masterbatch, additives or regrind with the virgin material to create the feedstock for the blow machine. There are three types of blow molding: extrusion, injection and stretch. In extrusion blow molding, a molten tube of plastic is extruded into a mold cavity and infl ated with compressed air. In this process, the thermoplastic in the form of small pellets or granules is first heated above the melting temperature and molded into a preform using injection molding process. These preforms are used to feed into the blow machine.
Extrusion blow molding is the most widely used technique. Sarlink is very suitable for blow machine because it has excellent melt strength and a high blow ratio. Sarlink gives a signifi cant weight reduction compared to thermoset rubber and Sarlink is fully recyclable. Table 1 shows an overview of application and material combinations.
The principle of the blow machine process is that a parison, which is formed by continuous extrusion of material and rotating of the screw in the barrel, is clamped between two halves of a mold, cut-off and infl ated with air to fi ll the mold. This process is typically used for automotive air intake ducts. An advantage of three dimensional blow machine is that it is possible to make complex parts without generating flash along the edges. There are different techniques to make 3D articles. To reduce lead time and expense, blow molders are now adopting FDM. In fi ve days or less, companies can design a blow machine, build the tool and blow mold near-production quality prototypes.
This process guide provides information on the application of FDM to injection blow molding. When producing prototype injection blow machine molded parts, combine these general guidelines with existing practices, procedures and preferences.
The injection blow molding process involves two stages. In the first stage, a plastic part called a preform is made, using a traditional injection molding process. The preform is a precise shape, with precise wall thicknesses. This preform is then transferred to a blow machine station, where it is placed in another mold and held in place by specific features of the preform that mate with the blow mold cavity.

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