Manufacturers have a clear idea about the difference between the two main processes of blow Moulding. However, to a layman, the entire concept may sound difficult to comprehend. To ease up this confusion, we will clearly spell out the differences between extrusion blow Moulding and injection blow Moulding.
EXTRUSION BLOW MOULDING PROCESS
It is a type of blow Moulding whereby the plastic is first melted at boiling temperatures. This melted plastic is then extruded into a tube. This tube is usually hollow. A better name for it will be prison. Air is then passed through it so that the plastic takes up the desired shape and be inflated. The plastic is then allowed to cool down. Once it is sufficiently chilled, the mould is opened and the item is ejected.
The products of Extrusion Blow Moulding Machines are Automotive Ducts, Traffic Safety Products, Stadium Seating and Chairs, Containers, Trays, Reservoirs, and Tanks, Coolers, Floats, Stands, Panels, and Doors, Toys and Sporting Goods, Watering Cans and Household Products and many more products.
INJECTION BLOW MOULDING PROCESS
It is again a type of blow Moulding process whereby a polymer is injected into a core pin. This pin is then allowed to rotate to a blow Moulding station where it is cooled and inflated. It is the least preferred blow Moulding process as it is used to manufacture only select items like small syringes.
The products of Injection Blow Moulding Machines are jars, dropper bottles, ovals – cylindrical and boston rounds, one piece roll-on deodorants, tablet and pill bottles and many more other products.
The first difference lies in the type of product which is produced by the respective processes. The extrusion blow Moulding process creates a two-dimensional product whereas the injection blow Moulding process creates a three-dimensional product as the final output. The second difference lies in the tool that is used in both the processes. For the former, a die is used to get the final output whereas the latter employs the use of a mold. The third difference is in the time taken to produce the final output with the two processes. The extrusion Moulding process is slower whereas the Injection Moulding process is faster. The kind of scrap or residue that remains behind makes for the fourth difference between the two processes. With the former, the scrap is with flash and trimming whereas, in case of latter, the scrap is without flash and trimming. The fifth difference is with regard to the part thickness of the machine used in both the processes. In case of extrusion, the part thickness depends on how much the material can be stretched during the process whereas, in case of intrusion, it depends upon the relationship between the core and the mold.
Extrusion Moulding is regarded as a pocket-friendly process when compared to injection Moulding. However, the quality of materials that are used varies from extremely poor to excellent. Styrene is a very poor material that is often used in this process. HDPE is excellent whereas PP and PC are just moderately good for use in the extrusion process.
The quality of all the four materials namely Styrene, PP, PC, and HDPE are excellent in the injection process. Hence it is a comparatively costly process.