Cutting System to Extruder

The downstream cutting system, which is also called pelletizing system or granulating system to either single screw extruder, twin screw extruder or multiple screw extruder determines the shape and quality of final plastics pellets based on the raw materials being processed.

Some tips of how to choose the right cutting system:

• Feature of the raw material including all additives
• Stability and reliability for production;
• Operation and maintenance;
• Pellet appearance

The following cutting systems for extrusion are the most popular cutters throughout the world.

It’s the most economical cutting system so far, easy to maintain and operate, applicable to most types of polymers.

The polyolefin is extruded from the die head like noodles, so some people call it literally noodle pelletizing.

This is the part where the raw material is extruded out. It’s normally equpped with either manual screen changer or other hydraulic screen changer or electrical changer.

This is used to cool down by water the strands/noodles coming out of the die head. In hot summer a condensor/chiller cooling the water may apply.

Normally matched with the water bath. It’s aimed to swipe off water by strong airflow. There’s is a basin collecting water so the water won’t go everywhere.

It cuts short the strands. We have two main types: one is called side wheel which means the cutting blade is installed at side and the other is called portal which has two supporters of the rotary cutting wheel.

This cooling has no water contact. The strands go through an “air tunnel” and get cooled. It’s good for highly filled compounds.

The main process of water ring cutter: the compounded long strip polymer is extruded out of the die head of plastic extruder. Then it is immediately chopped by the rotating blade as soon as it comes out. It is then thrown into the cooling water running at a high speed along the internal wall of cutting chamber. The chopped pellets will be conveyed with the water flow into the centrifugal dryer.

The advantages of a water ring granulator include:

1. The chopped granules by the water ring cutter have good uniform appearance. This makes it easy to control the quality for the next process.
2. The water ring cutting system is generally paired with vertical centrifugal dryers or drying vibro sieves. Compared with strand cutting system which has a cooling water bath, it needs less spacing.
3. Normally there’ll be a screen changer in front of the water ring cutter to filter plastic debris. For a strand cutter, replacing the screen will break the strands and need re-aligning, which takes labor and time. Water ring cutting system avoids this.
4. The cooling media water in the water ring is able to cool the raw polymer quickly. So it’s suitable for most kinds of polyolefins.

It’s used to remove water stuck on the chopped pellets by centrifugal force. The pellets are elevated from the bottom to the top.

Similar to the water ring cutter, this cutter uses air cooling instead of water when the pellets are chopped on the die plate. The polymer doesn't contact any water in this process.

Cyclone conveyor cools down the pellets. There is a vibroscreen seperator in the image.

The underwater makes very good-looking pellets. It’s applicable for almost all kinds of thermoplastics. We strongly recommend it for those with high viscosity polyolefins and it provides high output.

Some people also call this “underwater strand cutter”. This cutter is simple to operate. The raw material comes out of the die head then fall into the running water. The strands are cooled by the water current and then are chopped by the water slide cutter. The advantage is even though the strands/noodles tend to break, the operator needs no involving to rearrange. This is a perfect solution for recycled material which contains more contaminants than virgin.