The template of the extruder is composed of a die plate body with a discharge hole and a thermal insulation layer, and is fixed to the die head with a threaded rod. Only when the discharge speed of each die hole is consistent can particles of uniform size be cut.
In the process of use, there are many factors affecting the smoothness of the template. When the die plate is blocked seriously, the appearance of the product, the service life of the cutter, and the parking will be affected.
The cause of template plugging
1. Plugging during equipment shutdown, start-up and normal production
If the products in the processing and the discharging section are subjected to excessive thermal degradation during the shutdown of the equipment, it may cause sedimentation or carbonization in the critical state. If carbonization occurs in the die plate, it will cause inevitable blockage of the mold hole.
During the start-up process, the flushing die plate is not in place, which will also affect the smoothness of the die plate hole. At the same time, the setting of the time when the product, pellet water and granulator blade arrive at the template is critical to ensure a uniform product flow and produce a uniform pellet. The temperature of template and pelletized water also plays a key role in preventing hole plugging. Too low temperature of pelletized water will reduce the temperature of the template and increase the plugging rate. However, if the temperature of the granulation water is too high, the particles can not reach the cooling effect, and the sticky material may be produced.
2. Influence of product characteristics on template hole plugging
These high molecular weight polymers have low melt index and are not easy to mix completely. When the granulation output is low or the production fluctuates, especially when the granulator is in low-speed operation, the mold hole may be blocked due to the low discharge flow rate. The pressure of the high melting product itself on the template is reduced, which is not conducive to its scouring ability to the mold hole. Pay special attention to the change of die pressure during production. Although the die pressure is mainly affected by the pressure drop at the load, melt finger, screen changer and other components, the die pressure will rise rapidly when the die hole is blocked seriously.
3. Influence of formula conversion on template hole plugging
When the scheme is converted to high melt index products, if the products are mixed unevenly in the mixing section, some of the low melt index products enter the template, and because the temperature of the barrel and the template decreases too fast when the high melt index products are converted, the low melt index parts cannot be completely melted, and it is very easy to block at the hole.
4. Effect of load on template hole plugging
During the production process, it is often necessary to adjust the production load. High load and low temperature will inevitably lead to incomplete mixing, which will lead to blocking of die holes. Low load and high temperature will lead to too fast extrusion speed of materials in the cylinder at the template, which is easy to cause knife wrapping. The load adjustment should also avoid too fast and too large. In daily production, except for special needs, the adjusted load range should not exceed 5% of the current load.
The solutions of template plugging
- Properly increasing the temperature of granulation cylinder and template can enhance the flow performance of materials; High melt refers to that the temperature of the template and the pelletizing water can be properly increased before the product is converted to high melt, so as to melt through or improve the blocked mold holes.
- Properly increasing the load is conducive to flushing the mold hole, but the barrel temperature and template temperature must be properly increased to ensure complete mixing of the product. At the same time, if the cutter torque fluctuates, the load shall be reduced and the rotation speed shall be increased in time to avoid high torque interlocking shutdown.
- Turn down the pelletizing throttle valve to improve the mixing degree of the pelletizer. Especially during the production of high melt index products, it is necessary to ensure the complete mixing of the products.
- In case of long-term shutdown, the temperature of the processing section must be reduced, especially in the area with high working temperature, so as to avoid carbonization and precipitation caused by excessive thermal degradation of products staying in the processing section during shutdown.
- Before the start-up, the formwork shall be thoroughly inspected and cleaned. When washing the formwork, it shall be ensured that the formwork has been cleaned before closing the trolley. In order to prevent the sharp change of the instantaneous temperature when the granulated water contacts the formwork during the start-up, the temperature of the formwork can be appropriately increased in advance.
- The impurities of raw materials and the melting points of all subsequent additives shall be strictly controlled. At the same time, the fluctuation of additive addition amount will directly cause the mold hole to be blocked.