What is Extrusion? and why do we need an extruder screen?
Importance of extruder screen: Extrusion is a process in which melted material like polymer, plastic, rubber etc. is forcefully pass through a die with the help of screw.
In 90% extrusion techniques use a melt-through woven wire mesh screens that helps to filter out any pollutants before passing through to main dia. The wire mesh screens are fitted with the breaker plates which have holes. The breaker plates placed between screw or extruder and dia.
Woven wire mesh screens play an important role to improve mixing and protect gear pumps from being damaged by hard particles. To pump fine material, you need fine mesh shield.
Usually, the screen sets will install the supporting screen near breaker and main filter screen mesh or finest screen mesh towards the screw. This selection helps to save the screen from damage or blowing contamination via breaker plate holes and being torn or twisted from the rotating motion of the melt.
There is possible combination that a mesh screen pack has two screens for same woven wire mesh count at either end. Like: a mesh screen pack has following combination: 18 mesh * 120 mesh * 80 mesh *60mesh *20 mesh. This type of combination screen pack is same look wise from both ends, but we must ensure that the screen pack placed in right direction.
Some producers curious that the main filter screen (fine mesh) can stuck or stop larger particles during the extrusion flow. The supporters advise that it will helps to increase melt circulation and decrease the degradation.
Sometimes producers are worrying that wire mesh screen can propose new variables to the procedure which can increase the back pressure & melt temperature. Also, sometimes it affects the output as well. It requires more equilibrium which effect the final material cost.