How to guarantee the extrusion part quality?
Some of the many problems that can occur during extrusion are traceable to the processed raw material; that is, the raw material is not up to specification. Sometimes, we can find some foamy or bubbles on the profile surface. This may trace back the impurity of the thermal plastics.
But why this happens? -Improper Material addition
As we know, plastic resin materials such as nylon, polyurethane, polyester, and polycarbonate are very hygroscopic. They can absorb moisture rapidly from the air. At extrusion temperatures, moisture degrades these materials to lower molecular weight polymers, resulting in poorer property performance. Proper drying to eliminate moisture is critical to obtain the optimum property performance in the final product.
Other materials, e.g., acrylics, and acrylonitrile butadiene styrene (ABS), also absorb moisture from the air. They must be dried prior to processing. Any moisture in the polymer is converted to steam in the extruder and can cause surface imperfections such as splay, holes in the product, or a foamy product. With proper handling, these resins do not normally require additional drying prior to processing.
However, if the seal is broken on the container or the bag is not completely resealed after opening, the product will absorb moisture and have to be dried prior to extrusion. Polyesters are particularly sensitive to moisture and must be dried in dehumidifying dryers, transported with dry air, and blanketed with dry air in the extruder feed hopper.
Other problems include contamination with foreign materials such as metal chips. So every precaution must be taken to avoid contamination by closing bags, covering hoppers, keeping a clean area around the extruders, and similar measures.
To ensure an extrusion part quality through the extrusion process during manufacturing, it is essential to observe, control, and monitor all related parameters such as state of equipment, working conditions, temperatures, pressures, quality of dies, materials, and cooling medium and other obstacles during the whole manufacturing.
We H.D.Plastics has over 10 years of experience in the extrusion industry. Our engineer talents are very familiar with manufacturing processing and a standard SOP to monitor the whole processing. We take high priority on the incoming material inspection to make sure the exact material addition and purity of the material. So please don’t worry.