1. Raw Material Preparation and Mixing
Ingredients: Based on the performance requirements for the pipe, weigh out the resin (PVC, PE, etc.) and additives such as stabilizers, lubricants, and color masterbatches according to the formula.
Mixing: Use a high-speed mixer to thoroughly blend the raw materials to form a dry blend. For water-absorbent materials such as PE and PPR, drying is also required (to control moisture content below 0.02%) to prevent the formation of bubbles in the pipe.
2. Extrusion and Plasticization
Equipment: PVC pipes are typically produced using conical twin-screw extruders (suitable for forced feeding of powder); PE/PPR pipes are commonly produced using single-screw extruders (suitable for pellets).
Heating and Melting: The barrel is heated to melt the raw material. Typical processing temperatures are 160–190°C for PVC and 180–220°C for PE. Temperature fluctuations must be controlled within ±2°C to ensure uniform plasticization.
3. Molding
Molten plastic is fed into the extrusion die. The spiral flow channel design inside the die ensures even distribution of the melt, guaranteeing consistent wall thickness throughout the pipe, and ultimately shaping the melt into a continuous hollow pipe parison.
4. Cooling and Sizing
Vacuum sizing: The pipe blank passes through a sizing sleeve with internal grooves and an external vacuum. Under negative pressure (approximately -0.08 to -0.1 MPa), the outer wall of the pipe is drawn against the inner wall of the sizing sleeve, precisely controlling the outer diameter and roundness.
Cooling and Curing: The pipe passes sequentially through a spray vacuum setting chamber and a cooling water tank, where it is cooled to room temperature with cold water, becoming hard and stable.
5. Hauling, Marking, and Cutting
Hauling: A tracked hauler pulls the pipe out at a constant speed synchronized with the extruder's rotational speed (with an error margin of <0.1%), ensuring uniform wall thickness.
Marking: A spray coder or printer is used to print information such as specifications, standards, and brand names onto the pipe surface.
Cutting: Depending on the pipe diameter, fixed-length cuts are made using a planetary cutter (for large pipes) or a circular saw cutter (for small and medium pipes).
6. Stacking, Coiling, and Packaging
Small-diameter pipes (typically ≤160 mm): These pipes possess a certain degree of flexibility and are coiled into bundles using a dual-station coiler.
Large-diameter rigid pipes: These are neatly stacked using a turntable or an automatic stacking rack.
Inspection and Packaging: Finished products undergo final inspections for appearance, dimensions, and other criteria; those that pass are packaged and stored in the warehouse.