How to Set Parameters for Double Extruder Processing Ordinary Gloss Powder?

The requirement of highlight powder is high gloss, which means high glossiness, and it also places requirements on multiple indicators such as the number and density of curing points, which are closely related to the quality of the formula and its components, as well as the performance of the ACM. For the double screw extruder, the first is the mixing effect, and the second is the control of the generation of curing points.

All currently produced original double screw extruders, as long as they are qualified products, are suitable for processing highlight powder.

In order to ensure (improve) the mixing effect, the screw arrangement, the determination of gap values in various places, the contour and accuracy of the mixing block, and the temperature field of the barrel have all been determined. Therefore, our problem is how to use and give full play to the machine's performance.

Setting the melting zone temperature of the double screw extruder

We suggest that the set temperature T of the melting zone should be linked to the screw length-to-diameter ratio i and its speed n:

n≤200rpm T≈120℃, n=200-350rpm T≈140℃, n=500-800rmp T≈140℃ n=500-800rpm T≈150℃ When i=18, reduce by 5℃, and when i≥20, reduce by 10℃.

The final setting value depends on the melting state of the material on the screw, and should correspond to a length of one screw pitch from the front edge of the feeding port, where the material is basically not melted. The larger this length, the higher the set temperature of the melting zone, and vice versa.

Cooling water of the double screw extruder and its temperature control

Due to the fact that a considerable part of the power consumption in the operation of the screw is converted into heat, the components of the barrel are heated up, and the accumulation becomes higher and higher as it goes forward, so the temperature rise after the melting of the melt must be controlled. Otherwise, good mixing effect cannot be achieved.

Therefore, cooling devices are installed in each section. The smaller the temperature fluctuation during the entire process of opening and closing the cooling water, the better. However, at present, there is still a considerable proportion of machines that are not ideal, and their control range exceeds 10℃, which makes it difficult to ensure the mixing effect.

The accuracy of temperature control depends on the flow rate of cooling water and its temperature rise. The larger the flow rate and the smaller the temperature rise, the higher the accuracy. And the cooling water of the barrel should be soft water (small circulation).

Currently, higher-end machines on the market have this feature. It has a water tank that can be insulated, an water pump that can withstand a water temperature of 100℃, one for each control temperature zone, which sucks water from the water tank and enters the zone directly. After the hot water from each control temperature zone comes back, it is collected and returned to the water tank through a plate heat exchanger, and the water temperature inside the water tank is higher than that of the cooling water.

According to the softening point value of the melt in the material, as well as comprehensive factors such as the air temperature, set the water tank temperature, usually 50-80℃. When the water temperature in the water tank is higher than the set temperature, the solenoid valve in the cooling water channel of the plate heat exchanger is opened, so that the cooling water entering the temperature control zone of the barrel has a higher stable temperature, which reduces the temperature difference and achieves high-precision temperature control.

As long as customers provide the number of control temperature zones for their machines and the hourly output, our company can customize a set for you to improve the mixing effect of your machine.

Curing particles of double screw extruder

The reasons for the production of curing particles are many. It is a comprehensive factor, which is related to the quality of the formula and its components, even mixing different batches, and it is also related to the performance of ACM grinding, such as too high temperature rise in the grinding chamber, etc.

For the extruder, the first is that the gap between the screw and the barrel is too small or too large. When it is too small, the friction intensifies, and the local temperature rise is too high, causing the material to solidify; when it is too large, the self-cleaning ability is lost, and low-temperature solidification of materials is formed.

Secondly, the instability of the set temperature in each section, especially the discharge port section, where the actual temperature during operation is much higher than the set temperature, or if the discharge port has accumulated material for a long time, will also produce low-temperature solidified material.

Therefore, there are four main conditions for the good processing of highlight powder by the double screw extruder: first, the formula and high-quality components; second, the excellent performance of the machine with high-quality technical parameters; third, skilled operating techniques; fourth, good maintenance and timely repair, and avoid operating with illness.