Control factors in PVC pipe extruder production

During the production process, because PVC is a heat-sensitive material, even adding halogen-free flame retardants will only increase the dissolution temperature and increase the stabilization time without dissolution. This requires that the forming and processing temperature of PVC should be strictly controlled. Especially for PVC, because its production and processing temperature is very close to its dissolution temperature, dissolution is usually caused by unreasonable temperature control. Therefore, the extrusion temperature should be determined based on factors such as the formula, extruder characteristics, engine structure, screw speed ratio,  temperature measurement point location, temperature measurement instrument deviation, and temperature measurement point depth.

Temperature control

The control of temperature is an important control factor in extrusion operation. The temperature of the control factors required for extrusion molding is barrel temperature, machine diameter temperature, and die mouth temperature. If the temperature is too low, the melting will be poor, the appearance of the pipe will be dull, the physical properties will be poor, and the product quality will not meet the requirements: if the temperature is too high, the raw materials will dissolve and the product will discolor.

Screw speed ratio

The screw speed ratio increases and the extrusion amount increases, thereby improving efficiency, but it is easy to cause poor melting, causing the inner cavity of the pipe to be rough and the strength to decrease. At this time, the engine pressure should be adjusted to increase the production volume and The quality is better. The temperature control of the screw affects the material transportation rate, material melting, melting quality, etc. Extruded pipe fittings need to be circulated with cooling water to reduce the temperature of the screw rod, which is beneficial to improving the melting quality. The temperature of the cooling water flowing through the screw rod is around 50~70°C.

Traction belt speed

The adjustment of the traction belt speed is very important in the re-extrusion operation. The raw material is melted by extrusion, and is continuously extruded from the engine and then traction belt, and then enters the shaping equipment, refrigeration equipment, traction belt equipment, etc. The traction belt speed should be consistent with the the extrusion rate is consistent. Generally, during normal production, the traction belt speed should be about 1% to 10% faster than the extrusion speed of the pipe fittings.

Air compression and working pressure

Air compression can inflate the pipe fittings to maintain a certain concentricity.  It is stipulated that the working pressure should be appropriate. The working pressure is too small, the pipe fittings are not round, the working pressure is too high, the mandrel is cooled, the inner cavity of the pipe fittings is cracked, uneven, and the quality of the pipe fittings is reduced. At the same time, the pressure requirements are stable. If the pressure suddenly increases and sometimes decreases, the pipe fittings will easily cause the round bamboo to become damaged.

Temperature of die equipment and refrigeration equipment

To extrude different plastic products, different die methods and refrigeration methods are used. The refrigerated material can be gas, water or other liquids, and the temperature needs to be controlled. The temperature is mainly related to productivity, product thermal stress, etc.