Plastic PVC-U Injection Molding Process Settings
PVC – unplasticized (PVC-U)
Barrel Heating temperature:
feeding zone: 30～50°C (50°C)
Zone 1: 140 ~ 160 ° C (150 ° C)
Zone 2: 165 ~ 180 ° C (170 ° C)
Zone 3: 180 ~ 210 ° C (190 ° C)
Zone 4: 180 ~ 210 ° C (200 ° C)
Zone 5: 180～210°C (200°C)
Nozzle: 180～210°C (200°C)
The temperature in parentheses is recommended as the basic set value, the stroke utilization is 35% and 65%, and the ratio of module flow length to wall thickness is 50:1 to 100:1.
Melt temperature: 210 ~ 220 ° C
Barrel constant temperature: 120 ° C
Mold temperature: 30 ~ 60 ° C
Injection pressure: 80 ~ 160MPa (800 ~ 1600bar)
Holding pressure: can not be set too high, 40 to 60% of injection pressure, based on modules and gates
Back pressure: Due to its thermal sensitivity, it is critical to set the back pressure correctly; the heat generated by the screw friction (closed heat input control) is better than the heat generated from the barrel heating ring; the back pressure does not exceed 30 MPa (300 bar) )
Injection speed: Do not set too high and be careful of the shearing effect of the material; where the product is prone to denaturation or sharp edges, multi-stage injection speed should be absolutely required.
Screw speed: use the minimum allowable setting, the maximum speed of the line speed is 0.2m / s; if necessary, delay the plasticization to ensure that the metering operation can be completed at the low screw speed before the end of the cooling time in the case of long cooling time Need high torque and maintain uniformity
Measuring stroke: 1.0 ~ 3.5D
Residual amount: should be small: 1 ~ 5mm, depending on the metering stroke and screw diameter; the screw ensures minimum fit when installing the barrel
Pre-drying: If the storage conditions are not good, dry at 70 ° C for 1 h.
Recovery rate: allows recycling of materials without thermal decomposition
Shrinkage: 0.5% to 0.7%
Gate system: sprue, chip gate or wafer gate is better, point gate can also be used for small products; gate should have arc transition in the direction of the product
Machine downtime: turn off heating, no back pressure plasticization, allow the melt to settle 2~3mm, then operate the machine as slowly as the extruder; repeat the operation until the barrel temperature drops to 160 °C, then squeeze out the excess material, empty Cartridge
Barrel equipment: rigid PVC screw; some require a heating coil and a cold air blowing device; the screw head has a screw groove or no screw groove, straight through nozzle
