Porosity - Trapped Air in the Casting
Porosity is present in all diecastings and the amount of porosity will have a direct effect on the strength and performance of the casting. Load bearing diecastings will not meet strength requirements and decorative castings will show blistering which will result in high levels of rejects and wasted effort. Our Real Time controlled machines are the best in the industry and we consistently out-perform our competitors in terms of adherence to customers’ specifications.
The recent machines supplied by Frech have the added benefit of Pre-Fill. This options allows us to send the machine piston down a pre-set amount forcing air out of the machine before the die closes. This means the air contained in the process is the volume of air of the cavities and runner and excludes the air normally trapped in the nozzle and gooseneck feature of the machine. Running our machines with the Pre-Fill option reduces total porosity in the casting by as much as 15%. On average we consistently maintain porosity at around 1.5% to 2.3% which is significantly below the industry average of between 3% and 5%.
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This section of a zinc diecasting shows low levels of porosity which can be achieved through correct programming and advanced machine facilities such as Pre-Filling. As part of our routine quality control we measure porosity against agreed levels with our customers to ensure each batch of castings is manufactured correctly. |
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The dark areas indicate entrapped air referred to as porosity. Excessive porosity can cause weakness in the casting and also prevent successful post casting processes such as powder coating and plating. If the casting is subjected to higher temperature over 100 deg. C the entrapped air expands and creates blisters or blow holes on the surface. |
