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The below article can be used for machine setters and machine operators of injection moulding machines.
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How to calculate the specific injection pressure in injection moulding.
EXAMPLE 1
Given the following information, for a hydraulically actuated injection moulding machine, calculate the specific injection pressure used with a set hydraulic pressure of 118 bar.
- Diameter of Screw = 35 mm
- Diameter of Hydraulic Injection Cylinder Piston =130 mm
- Actual Hydraulic Injection Pressure used =118 bar
Hydraulic to specific Injection Pressure = Area of injection cylinder piston / Area of screw x hydraulic pressure
Specific Pressure = Area of cylinder piston / Area of screw x hydraulic pressure
Procedure: Insert information known
NB For all calculations convert mms to cms (divide by 10). The reason for this change is that 1 bar = 1 kg/cm2.
STEP 1 – Calculate the area of cylinder piston
Use formula you are most comfortable with.
Area of cylinder piston = π x D x D/2.2 or πR2
R = radius
D = diameter
π = Pi = constant (3.142)
Therefore: 3.142 x 13 x 13/4 or 3.142 x 6.5 x 6.5 = 132.75 cm2
STEP 2 – Calculate the area of the screw
Use formula you are most comfortable with.
Area of cylinder piston = π x D x D/2.2 or πR2
R = radius
D = diameter
π = Pi = constant (3.142)
Therefore: 3.142 x 3.5 x 3.5/4 or 3.142 x 1.75 x 1.75 = 9.62 cm2
STEP 3 – Calculate the speci!c injection pressure
Area of cylinder / Area of screw x Hydraulic pressure = Specific injection pressure
132.75 cm2 / 9.62 cm2 x 118 bar = specific injection pressure
Therefore: 1628 bar specific injection pressure