General Purpose Screws (GPS)
The advantage of a GPS is that they can be used with most plastic materials such as PP, PE, Nylon, PET and PC so they are very flexible and good for moulding companies that mould a variety of different materials.
The disadvantage is that, for some materials, part quality and productivity rates will be lower compared to more advanced injection molding screw designs such as the barrier screw.
This type of screw provides a better quality melt at a faster rate compared with a GPS. There are many different designs of barrier screws, the difference being in the varying of the flight depths and channel widths.
The exact design chosen must be in line with the application.
Double Flight Screws
Although double flight screws have a different design, they are an alternative to barrier screws. They are also designed to deliver a high quality melt at fast rates.
The design ensures the plastic is fully melted before it reaches the compression zone, which is not the case in a GPS.
Double flight injection molding screws can be used in technical parts for PP and thin wall technical parts in PA which does not plasticize well with barrier screws.