This diagram is a simple illustration of how to gate and how not to gate. If a part with sections of varying thickness is gated in the thin part, the thin part freezes off too soon to allow the thick part to be sufficiently packed.
Severe shrinkage occurs in the thick part and warpage results.
Gating in the thick part allows both parts to be adequately packed before gate freeze-off, allowing for more uniform shrinkage. Here is a more detailed example of the effect of gate location. This diagram is an idealization of an automotive sail panel. The part is 100 cm long and exhibits a curvature. Two different gate locations were used in doing shrinkage calculations for this part.