A short shot is the incomplete filling of a mold cavity which results in the production of an incomplete part.
If a part short shots, the plastic does not fill the cavity fully. The flow freezes off before the flow paths have completely filled.
The average wall thickness(S) must be checked and confirmed in at the very beginning of mold design when deciding the gate location and the quantity of gate. the following is a general rule:
For a specific part, the other items must be considered when deciding the gate to prevent the short shot:
- Flow restrictions. Due to channels freezing or inadequate runner design.
- Hesitation and long or complex flow paths.
- Inadequate venting. Back pressure due to unvented air traps can cause a short shot.
- Low melt and/or mold temperatures.
- Insufficient material entering the cavity. An undersized machine, low shot volume, or inadequate ram speed.
- Machine defects. Including an empty hopper, blocked feed throat, or a worn non-return (check) valve that causes loss of pressure or volume leakage.
Example of solving the short by relocating the gate:
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