The dimensions of the box are shown in Figure 10.8: all dimensions are in cm. Young’s modulus of elasticity: 300,000 N/cm2Ĭoefficient of friction (PS on steel): 0.4Ĭoefficient of linear expansion (PS): 0.00007 cm/☌ Calculate whether this is sufficient given the following data: The machine has an ejector force rated at 40 kN. *Note that the units of length here are all in cm.Ī two-impression thin walled box-shaped component is to be moulded on a 275 tonne press. Δt= (polymer softening temperature) □ (mould tool temperature) (☌) ∝= the coefficient of linear expansion of the polymer (cm/☌)* ![]() Μ= coefficient of friction, polymer on steelĭ = the diameter of a circle whose circumference is equal to the total projected perimeter of the moulding (cm)* This is the way the formula is usually written in scientific texts but a slightly easier form for computational purpose is:Į = Young’s modulus of the polymer (N/cm2)*Ī = total surface area of moulding in contact with cavity or core, in line of draw (cm2)* The following formula may be used for calculating the ejection force: However, to avoid confusion the traditional 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. ![]() 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. This is the acceleration imparted to a 1 kg force by its own weight (1 kg-force). The acceleration due to gravity is normally taken as 9.81 m/s2. One newton is defined as the force necessary to give a mass of 1 kg an acceleration of 1 m/s2. The basic SI unit of force is the newton, which has the symbol N.
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