the fifth principle for deciding on the parting line is easy to machining. For instance, a slanted parting line and a curved parting line, they just require only one slanted or curved surface to match the mold plate, that is no problem and it is a better design, but a design require matching multiple surface, creating more technical challenge, while wasting time and effort.
The parting surface is the surface which is convenient for the product can be taken out successfully. Therefore, the position of parting surface should be selected at the part with the largest product section size. This is a basic principle.