Process parameters of PVC plastic
Cylinder temperature feeding area 30 ~ 50 ° (50 °)
Area 1 140 ~ 160 ° （150 °）
Zone 2 165 ~ 180 °（170 °）
Zone 3 180 ~ 210 ° （190 °）
District 4 180 ~ 210 ° （200 °）
Zone 5 180 ~ 210 °（200 °）
Nozzle 180 ~ 210 °（200 °）
The temperature in brackets is recommended as the basic setting value, the travel utilization rate is 35% and 65%, and the ratio between the mold length and the wall thickness is 50:1 to 100:1.
The melting temperature of 210 ~ 220 ° C
Cylinder constant temperature of 120 ° C
Mold temperature 30 ~ 60 ° C
Injection pressure: 80~160Mpa (800~1600bar);
The pressure should not be set too high, the injection pressure of 40~60%, based on the mold and gate.
Because of its thermal sensitivity, it is crucial to set the back pressure correctly. The heat generated by the rotation of the screw (turning off the heat input control) is better than the heat generated from the heating coil of the cylinder. Back pressure no more than 30Mpa(300bar)
The injection speed should not be set too high and the material will produce shear effect. Where products are prone to denaturation or sharp edges, a multistage injection rate is absolutely necessary.
The maximum speed of the screw speed is 0.2m/s. If necessary, delay plasticization to ensure that when the cooling time is prolonged, the metering operation can be completed before the cooling time is completed before the cooling time is completed; High torque is required to remain uniform.
Measuring stroke 1.0~ 3.5d.
The residual amount should be smaller: 1~5mm, depending on the measuring stroke and screw diameter; The screw ensures minimum coordination while mounting the barrel.
prebake If storage conditions is not good, at 70 ° C temperature drying 1 h
The recovery rate allows the material to be recycled without thermal decomposition.
Shrinkage rate by 0.5 ~ 0.7%;
Gate system sprue; Plate gate or round plate gate is better, small products can also use point gate; The gate should have an arc transition in the direction of the product.
When the machine is shut down, the heating is turned off, no back pressure plastification is allowed, and the solution is allowed to flow for 2~3min, then slowly operate the machine like extrusion. Repeat until the cylinder temperature below 160 ° C, and then squeeze out excess stock, empty cylinder
Rigid PVC screw for material barrel equipment; Some of them require a heating coil and a cold air device; The screw has a screw slot and a straight nozzle.