Clamping Force is one of the main parameter in Blow Moulding. It restricts the size of container can be molded on a particular machine. The clamping force is required to balance the force created inside the container by blowing air. Blow molding machines don’t require very high tonnage like Injection molding machines.
For a standard 3-plate single cylinder direct mould clamping unit, the clamping force is calculated as below:
Clamping force (N) =cylinder Area (mm2) x Pressure (bar) /10
Clamping force (kgf) =cylinder Area (cm2) x Pressure (kg/cm2)
Clamping force (lbf) =cylinder Area (in2) x Pressure (pound/in2)
For example, if a unit has 100 mm dia and applying a pressure of 100 bar, then
Clamping force, N = 50 x 50 x 3.14 x 100 / 10 N
= 78500 N
= 78.5 kN
Clamping force, kgf = 5 x 5 x 3.14 x 101.9716 kgf (1bar=1.019716kg/cm2)
= 8004.77 kgf
= 8 Ton
Clamping force, lbf = (5/2.54) x( 5/2.54) x 3.14 x 1450 lbf (1bar=14.5psi)
= 17643 lbf
If the machine has more than one cylinder, multiply the result by the quantity of cylinders.
Now this helps us to find out the clamping force, but how you decide on what clamping force is required for a certain container? That depends on the blowing pressure and inside area of mold & pinch off length. The thumb rule is
Total Clamping force (kgf) = Surface Area (cm2) x Air Pressure (kg/cm2) /2.5
+ Total Pinch Off Length (cm) x 200
The 2.5 divider in first part is an assumption factor for round drums to find out the force acting in mold clamping direction. The 200 multiplier in second part is based on that 1 Ton clamping force is required for every 5 cm pinch off.
For a standard 3-plate single cylinder direct mould clamping unit, the clamping force is calculated as below:
Clamping force (N) =cylinder Area (mm2) x Pressure (bar) /10
Clamping force (kgf) =cylinder Area (cm2) x Pressure (kg/cm2)
Clamping force (lbf) =cylinder Area (in2) x Pressure (pound/in2)
For example, if a unit has 100 mm dia and applying a pressure of 100 bar, then
Clamping force, N = 50 x 50 x 3.14 x 100 / 10 N
= 78500 N
= 78.5 kN
Clamping force, kgf = 5 x 5 x 3.14 x 101.9716 kgf (1bar=1.019716kg/cm2)
= 8004.77 kgf
= 8 Ton
Clamping force, lbf = (5/2.54) x( 5/2.54) x 3.14 x 1450 lbf (1bar=14.5psi)
= 17643 lbf
If the machine has more than one cylinder, multiply the result by the quantity of cylinders.
Now this helps us to find out the clamping force, but how you decide on what clamping force is required for a certain container? That depends on the blowing pressure and inside area of mold & pinch off length. The thumb rule is
Total Clamping force (kgf) = Surface Area (cm2) x Air Pressure (kg/cm2) /2.5
+ Total Pinch Off Length (cm) x 200
The 2.5 divider in first part is an assumption factor for round drums to find out the force acting in mold clamping direction. The 200 multiplier in second part is based on that 1 Ton clamping force is required for every 5 cm pinch off.
