The racetrack effect occurs when flow races through thick sections of the cavity before the thin sections have filled.
NOTE: Thick sections offer less resistance to flow than thin sections.Racetrack Effect
The racetrack effect indicates unbalanced flow paths and can often cause unnecessary weld lines and air traps. The following diagram shows a part with a thick rim.
The flow of plastic (red arrows) races around the rim, trapping a pocket of air (blue circle).
What to do
A large difference in wall thickness throughout a part can cause problems, but is sometimes necessary from a design point of view. However, in the previous example, the racetrack effect through the thick regions is not actually the problem. The problem is unbalanced flow that allows the racetrack effect to occur. If the plastic reached all parts of the thick rim at the same time, the racetrack effect would not occur.
Design Example I:
Design Example II:
01.Confirming Part Data
02. The Overall Design,Mold Base and Settin
03.The Shape Forming Component
04.Feeding & Gating System
05. Undercut Releasing System
06. Ejection System
07.Supporting System
08. Cooling & Heating System
09. Venting
10. Hot Runner System
11.Safety Switch/Data Code/Hydraulic /pneumatic System