Extruder Screen Pack

Extruder screens are manufactured to lots of different specs. The mesh that makes up the screen will be the exact opening size for your process and the size and shape will be dictated by your machines.

Here is how an extruder screen is made: 

1.  Wire mesh specifications with an appropriate micron rating are chosen
2.  Materials are layered and joined together in a spot welding operation
3.  Spot welded material continues on to a punching operation utilizing compound tooling
4.  The resulting Extruder Screens are separated from skeleton/waste material
5.  Finished Extruder Screens are cleaned
6.  Clean Extruder Screens are shrink-wrapped in preparation for shipping

Components

There is a misconception that since extruder screens are not reusable, they are easy to make or a “cheap version” will do. This is not the case.

Extruder screens are a key part of any polymer or plastics extrusion process.

There are a few key components to an extruder screen that we want to cover. These components should help you select the best manufacturer for your processes to offer long-lasting and reliable screens.

Welding

It is important to choose a manufacturer that welds your screens properly. While extruder screens are available from all over the world at different price points, quality is key.

Your screens need to be welded properly to ensure they don’t bend, stretch or break. This type of effect can alter the opening sizes in your mesh and change your filtration results.

This will also result in needing to change your screens more often and in the end, will cost you more money.

Wire Mesh Screen

he mesh in your screen, whether single-layer or multi-layer, needs to hold up against the material you are filtering. You don’t want your screen to rust or corrode during your process.

Stainless steel is preferred if the polymer being processed could corrode mild steel, or if the chance for contamination by oxidized steel screen material should be avoided.

A nickel-alloy mesh should be used for extruding fluoropolymers that could corrode typical stainless steels.

Opening size and weave type are also important to the quality of the screen.

Micron ratings/mesh counts vary widely depending on your desired outcome.

Square mesh is most widely used for its flow capability, but filter weaves (Dutch Twill and others) can also be used for finer filtration.

Typical square mesh counts and associated micron ratings will range from 18 mesh (1000 micron) to 500 mesh (25 micron).

Single-layer or Multi-layer

Extruder screens can be made with both one layer of wire mesh or multiple layers. A single-layer is used when virgin material with few impurities is being processed.

Multi-layer is used when reground or recycled material is being used or when absolute cleanliness is a must. There is typically a more coarse protection layer that the melted polymer first comes in contact with.

This protects the finer filtration layer or layers from debris damage, pressure, or the swirling motion of the plastic melt.  Another coarse layer faces the breaker plate to support and protect the finer mesh layer from being pushed into the breaker plate holes.

Configurations vary depending on a wide variety of factors, such as material type and cleanliness requirements, but extruder screens typically contain 2 to 5 layers.

That layer could be held together with spot welds, a rim-binder, or the layers could simply be unsecured and stacked in the desired configuration.

Shape

Extruder screens usually come round or kidney-shaped. Round screens are usually used one at a time and the filtration process is stopped in order to change the screen.

Kidney-shaped screens are used in multiples around a screen-changing wheel that automatically advances to the next screen when clogging or a pressure increase is detected.  This type of system allows the process to run uninterrupted and an operator can replace clogged screens while the melt flow continues with new screens.

Size

Sizes vary widely with each style. Depending on the type of material and volume desired, round screens can be less than 1” in diameter or exceed 16” in diameter.

Likewise, kidney-shaped screens typically range in size from 2.5” x 3” to larger than 3.5” x 6.5”.