Some enterprises in the production of PE pipe diameter is between 5.8-5.95mm, customer requirements, sometimes have a slightly larger diameter, sometimes slightly smaller, how to control the stability?
When extruding tube, the outer diameter of pipe is not only related to the size of die, but also to the speed of extruder and the speed of pipe drawing, and also to the speed of cooling and the uniformity of cooling.
When the extrusion speed is constant, if the traction speed increases, the outer diameter of the tube will be smaller due to the tensile effect, and the wall thickness of the tube will become thinner. If the traction speed decreases, the melt will stagnation at the mouth die, which will increase the wall thickness of the tube and increase the outer diameter. In the extrusion process, the traction speed and extrusion speed must be well matched and kept constant. If the extrusion speed or traction speed of the extruder is unstable and fluctuated, it will cause the fluctuation of the pipe outer diameter and the phenomenon of large and small time.
The pipe extrusion, if the cooling fast, the longitudinal tensile degree when drawing pipe in small pipe diameter, wall thickness is large; if the slow cooling, high degree of longitudinal tensile pipe drawing pipe, small diameter, wall thickness is small; if the cooling water flow rate or the temperature is not stable, when large or small high low, it will cause uneven cooling pipe vertical, longitudinal tension level is not the same, and the outer diameter of the pipe appear unstable, big and small.
In the process of production, there are several measures to control the stability of the diameter of the pipe.
(1) the extrusion speed is well matched with the traction speed, and the ratio of the two is kept stable.
(2) to keep the cooling water flow of the cooling system or stable and stable, often check the work of the limit valve of the setting box water is normal and reliable.
(3) often check the pressure of vacuum compressed air, keep the vacuum pressure steady in vacuum setting, and make the speed of traction stable.