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The basic SI unit of force is the newton, which has the symbol N.One newton is defined as the force necessary to give a mass of 1 kg an acceleration of 1 m/s2. The acceleration due to gravity is normally taken as 9.81 m/s2. This is the acceleration imparted to a 1 kg force by its own weight (1 kg-force). Hence:
Ejector Design Software to do conceptual design and generate ejector sizes The ejector design principles used in the ejector calculations for the program are explained including the ejector energy balance and effects of the ejector flow cones. Ejector Design Calculation; Steam Ejector Design Calculation; Ejector Design Calculations; Online Ejector Screening process Software Transvac designers have created an on the internet software programme to enable our customers to operate preliminary Ejector screening, to make the technologies more available to Designers across the essential oil gas and process industries. Simulation software is not applicable for many gas/gas ejector applications encountered. Gas ejector design can however be determined by rigorous calculation using the applicable equations 1, 2. A study was performed to establish a simpler methodology for ejector design and for the prediction of performance, based on the following.
Lumen 1 0 0 download free. 1 kg-force = 9.81 N
1 tonne-force = 9810 N or 9.81 kN
1 tonne-force = 9810 N or 9.81 kN
Note: For less precise calculations the value of g is often taken as 10 m/s2. The SI unit of pressure and stress is the pascal, which has the symbol Pa.
1 Pa = 1N/m2
1MPa= 1 MN/m2 or 1 N/mm2
1 GPa = 1 GN/m2 or 1 kN/mm2
1MPa= 1 MN/m2 or 1 N/mm2
1 GPa = 1 GN/m2 or 1 kN/mm2
Note: The SI system actually uses the designation 9/81 ms–2 for the acceleration of gravity (g) and a similar system for other units. However, to avoid confusion the traditional
designation is being used here.
designation is being used here.
Formulae
The following formula may be used for calculating the ejection force:
The following formula may be used for calculating the ejection force:
This is the way the formula is usually written in scientific texts but a slightly easier form for computational purpose is:
Nik collection 2 by dxo 2 5 0 6. where:
Fp = the ejection resistance force (N)
E = Young’s modulus of the polymer (N/cm2)*
A = total surface area of moulding in contact with cavity or core, in line of draw (cm2)*
Fp = the ejection resistance force (N)
E = Young’s modulus of the polymer (N/cm2)*
A = total surface area of moulding in contact with cavity or core, in line of draw (cm2)*
μ= coefficient of friction, polymer on steel
m = Poisson’s ratio
d = the diameter of a circle whose circumference is equal to the total projected perimeter of the moulding (cm)*
∝= the coefficient of linear expansion of the polymer (cm/°C)*
Δt= (polymer softening temperature) ? (mould tool temperature) (°C)
t = average wall thickness of part (cm)*
Form gui editor patch. *Note that the units of length here are all in cm.
d = the diameter of a circle whose circumference is equal to the total projected perimeter of the moulding (cm)*
∝= the coefficient of linear expansion of the polymer (cm/°C)*
Δt= (polymer softening temperature) ? (mould tool temperature) (°C)
t = average wall thickness of part (cm)*
Form gui editor patch. *Note that the units of length here are all in cm.
Example
A two-impression thin walled box-shaped component is to be moulded on a 275 tonne press. The machine has an ejector force rated at 40 kN. Calculate whether this is sufficient given the following data:
A two-impression thin walled box-shaped component is to be moulded on a 275 tonne press. The machine has an ejector force rated at 40 kN. Calculate whether this is sufficient given the following data:
Material: Polystyrene (PS)
Young’s modulus of elasticity: 300,000 N/cm2
Poisson’s ratio: 0.35
Coefficient of friction (PS on steel): 0.4
Softening temperature of PS: 80 °C
Mould tool temperature: 20 °C
Coefficient of linear expansion (PS): 0.00007 cm/°C
The dimensions of the box are shown in Figure 10.8: all dimensions are in cm.
Young’s modulus of elasticity: 300,000 N/cm2
Poisson’s ratio: 0.35
Coefficient of friction (PS on steel): 0.4
Softening temperature of PS: 80 °C
Mould tool temperature: 20 °C
Coefficient of linear expansion (PS): 0.00007 cm/°C
The dimensions of the box are shown in Figure 10.8: all dimensions are in cm.
Total area of resistance = 2 x (12 x 15) + 2 x (12 x 25) = 360 + 600 = 960 cm2
Total projected perimeter = 2 x 15 + 2 x 25 = 80 cm
Hence:
d = 80/π = 25.46 cm and Δt = 80 ? 20 = 60 °C
Therefore,
Total projected perimeter = 2 x 15 + 2 x 25 = 80 cm
Hence:
d = 80/π = 25.46 cm and Δt = 80 ? 20 = 60 °C
Therefore,
p F = 13 824 N, or 13.8 kN
Ejector Design Calculation Software
Hence for a two-impression tool we require 2 x 13.8 kN = 27.6 kN. This is well within the machine specification of 40 kN; however, in practice the machine ejection force will also be subject to the sliding resistance of the ejector system and sometimes to force
exerted by any return springs used in the ejector assembly.
exerted by any return springs used in the ejector assembly.
Gas Ejector Design Calculation
A good rule of thumb is to apply a factor of 1.25 for nonspring systems and 1.5 for spring return systems. Therefore, in this case the total ejection resistance force is:
1.25 X 27.6 = 34.5 kN for non-spring systems, or
1.5 X 27.6 = 41.4 kN for spring return systems
This demonstrates that the machine ejection force is satisfactory for the first case but unsatisfactory for the second case.
1.5 X 27.6 = 41.4 kN for spring return systems
This demonstrates that the machine ejection force is satisfactory for the first case but unsatisfactory for the second case.
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