The key to a successful die casting is an excellent tool design. One of the hardest components to design and maintain for good tool life is a core pin. A “core” is the separate and replaceable part of the die that forms an internal feature of the casting. Core pins come in all shapes and sizes, but the most commonly used shape design is circular. Core pins may be fixed to the die cavity or to a slide, actuated through the mechanical opening/closing of the die, or by hydraulic cylinder or other means. While core pins are the backbone of good tool design, when not properly designed, it can result in severe downtime and inefficient productivity.
On a high-volume die casting project for heat sinks, there were 24 core pins. After the PPAP process, there was an unexpected increase in downtime (every 1000-2000 shots) along with core pins breaking. The team in charge of the project, began their analysis.
Root Cause Analysis
An MES quality engineer, along with the tooling engineer and supplier team, evaluated various reasons using a fishbone diagram. There were three critical reasons identified:
1.) Guide show wear out in the machine
2.) Guide pillar/guide bush wear out in the die
3.) Weaker core pin in the die