1. Determining the stability and uniformity of pipe dimensions
Fluctuations in material feed cause uneven wall thickness: If the feeder operates unevenly or the variable-frequency drive system has a delayed response, the amount of material entering the extruder will vary. These fluctuations are directly reflected in the final product, resulting in increased wall thickness tolerances and axial wall thickness variations. For pressure pipes with strict specifications, this can directly lead to reduced pressure-bearing capacity and even bursting during use.
Impact on fixed-length cutting accuracy: For production lines equipped with meter-counting fixed-length cutting systems, fluctuations in feed rate can cause unstable extrusion speeds, resulting in errors in cutting length and increasing the scrap rate.
2. Factors Affecting the Mechanical Properties of Pipe Materials
Drying efficiency determines internal defects: PP resin is hygroscopic. If the drying unit in the feeding system (such as a hopper dryer) is ineffective, moisture in the raw material will enter the high-temperature melt zone along with the screw. Hydrolysis causes molecular chain breakage, and since water vapor cannot escape, it ultimately forms bubbles or silver streaks inside or on the surface of the pipe. These microscopic defects severely weaken the pipe's tensile strength, impact resistance, and long-term resistance to static pressure. They act as stress concentration points, leading to premature rupture of the pipe when subjected to stress.
Mixing uniformity determines performance consistency: Many PP pipe formulations contain various additives such as color masterbatches, antistatic agents, and UV stabilizers, or glass fiber-reinforced materials. If the mixing device of the feeder performs poorly, the additives or reinforcing phase cannot be uniformly dispersed in the matrix, leading to localized performance variations in the pipe. For example, areas where glass fibers aggregate are prone to surface roughness and stress concentration, while areas lacking glass fibers suffer from insufficient strength.
3. Factors Affecting the Appearance Quality of Pipe Materials
Formation of Black Spots and Crystalline Spots: If there are hard-to-clean dead spots (commonly known as "material buildup zones") within the feeding system, PP material that remains stagnant for extended periods will be repeatedly heated at high temperatures, causing thermal-oxidative degradation and forming yellowish-brown carbonized residues. These degradation products are periodically carried away by new material and mixed into the melt, resulting in black spots, charred particles, or yellow streaks on the pipe surface, which severely compromises the product's appearance.
Causes of Surface Roughness: Uneven material feeding or incomplete drying not only produces bubbles but also impairs melt flow. As a result, when the pipe passes through the die and the finishing sleeve, the surface cannot fully replicate the die's smoothness, resulting in a rough, dull-looking final product.
4. Impact on Production Stability and Energy Consumption
"Bridging" Causes Feed Interruptions: If the feed hopper is poorly designed, or if the raw material (especially recycled regrind) has an irregular shape, "bridging" (where material accumulates in the hopper without falling) can easily occur, leading to sudden feed interruptions. This causes a sharp drop in pressure within the extruder, resulting in pipe sections with material defects and poor plasticization; in severe cases, it may even require a shutdown to clean the die.
Unstable feeding increases energy consumption: The screw must overcome the additional resistance caused by fluctuations in material supply, resulting in frequent fluctuations in the main motor current. This not only increases energy consumption but also accelerates wear on the screw and barrel.