TABLE OF CONTENTS The purpose of this summary is to bring together in one section, all the formulae in the book for convenience.
When a new mould tool is being considered, however, the expression is rearranged to estimate the number of impressions necessary to achieve a desired production rate:
where:
M = the shot mass in kg
H m = enthalpy at the material melt temperature in kj/kg
He = enthalpy at the moulding ejection temperature in kj/kg
The cooling capacity required is then this value divided by the cycle, i.e.,
where Q ? = the cooling capacity in kj/s.
For maximum cooling efficiency there should be a difference of 5 C between the cooling inlet and outlet temperatures.
The specific heat of water is 4.19. Therefore, it takes 4.19 kj of energy to increase the temperature of 1 kg of water by 1 C. Hence to raise it by 5 C we would need 5 4.19 = 20.95 kj.
The volumetric flow of water required to remove the heat in the mould is given by
We also need a linear flow rate of 2.5 m/s to promote turbulent flow, hence the volumetric flow can also be expressed as Vf = 2.5 x cross-sectional area of channel. If the channel is circular we can write this as:
Transposing for d gives:
There are three equations that may be used which give a sufficiently accurate result for most moulding conditions:
