We explain the method of using mold shrinkage to determine the mold core size.
First, determine the molding shrinkage rate α
Example α=0.005
Secondly, select the size of the molded product that needs to be determined (when the size tolerance is ± tolerance)
Example) 22±0.05
Next, use [Formula 2] to calculate the required mold core size
Lo=(1+α))×L…【Formula 2】
Lo: the size of the fixed mold core (mm)
L: The size of the molded product (mm)
α: Molding shrinkage rate
Example) Lo=(1+α)×L
=(1+0.005)×22
=1.005×22
=22.11
Therefore, 22.11mm can be obtained as the theoretical target size of the fixed mold core.
However, due to the full consideration of the machinability of the calculated size of 22.11mm and the correction of the mold after trial production, some further adjustments are required. Although mold parts with a width of 22.11mm are considered as machining, today’s machining equipment can reach it, but when the size is indicated in 0.01mm units, it is recommended to modify the mantissa of 0.01 to an even number.
However, if it must be an occasion that requires precision processing, it is also possible to retain the measurement results of 22.11.
Since the fixed mold may be repaired later, it can be made a little smaller.
In the case of a dynamic mold, it can be slightly larger.
If there is a good empirical judgment basis for mold correction, there is no need to make such numerical adjustments.