The extruder screw can be cleaned by the normal replacement method or by using special detergent, the former method will consume a lot of resin.
Using a small amount of water to clean the extruder screw can reduce the cleaning time and avoid the appearance of crystal points during production. The specific steps are as follows (the following amount is set based on the typical extruder screw with a diameter of 90mm, L/D= 28).
(1) Set the extruder screw to rotate at a low speed of 10r/min.
(2) Add coating grade LDPE to the cleaned material.
(3) The extruder screw runs at a high speed for about 10min to allow LDPE to completely replace the original material.
(4) Insert a plastic tube into the raw material of the hopper, and slowly inject 100~200ml water into the extruder screw.
(5) After a few minutes, the foaming will start from the middle of the melt curtain before developing to full foaming.
(6) The melt will become clean again after the foaming process. After 15-20 minutes, you can reduce the speed of the extruder screw and add new material.
(7) Finish the operation and start production.
Another commonly used method to clean the extruder screw is variable speed flushing, which is also known as the disco flushing method. The steps are as follows:
(1) The extruder screw runs at a medium speed to remove the stored material.
(2) Change the flow sequence.
(3) If it is not cleaned with crystal spots and debris, you should continue the above steps until it becomes clear.
You can use it directly without making other changes if it is switched from LDPE to EVOH. If it is switched from HDPE, PP, LLDPE to EVOH, you should first replace it with LDPE before using EVOH for extrusion. Especially after using PA and PVC, you should make sure to completely replace the resin in the barrel and die with LDPE before extruding with EVOH.
(2) Resin temperature
Please note that the temperature setting of the barrel and die as well as the control of the rotation speed of the extruder screw should not exceed 240℃.
(3) Detention time
It is based on 30 minutes. If the operation is interrupted for a long time, the extruder screw should rotate at a low speed to maintain the operation.
(4) Clean after the operation
If replaced with LDPE, it can be cleaned effectively in a short time.
(5) Notes for cleaning resin
Please do not use PP or HDPE when pre-cleaning or cleaning. There might be some problems if these resins contact with EVOH, and they will lead to difficult cleaning and caking.
Lesun is a screw barrel manufacturer which specializes in the production of parallel and co-rotating modular screw elements, extruder screws and barrels, covering Ø20mm to Ø300mm models. After ten years of vigorous development, we currently have many advanced CNC machine tools and special processing equipment for screw manufacturing. Besides, our machining operations have basically achieved intelligence and automation currently.
Our advanced processing methods, strong technical force, and sophisticated processing technology ensure that the quality and technical indicators of each production fully meet customer requirements. Welcome to consult.