How to determine the cause of die flash

How to tell when your die isn't shutting off

If you observe any of the following delays in your operation, chances are, it is due to a die that is not shutting off correctly.

If the operator waits after the die is fully locked before pouring metal, the die is cooling and the cycle time is extended.
If the operator delays hitting the shot button or the machine waits after the auto ladle pours, the metal is cooling in the cold chamber. This is a technique used by die cast operators around the world, to reduce flash.

What is happening in each of the above events is that the operator is compensating for a die that is not sealing properly. The operator has learned that by cooling the metal, it will not flash as bad or maybe not at all. However, he is costing the operation money. You are throwing away BTU. The process is designed to operate at an optimum temperature. It is also designed to operate with a die that is sealed off except at the vents. When the shot is delayed, you are paying to heat the metal, and then he is cooling it below the proper operating temperature. While this may eliminate or reduce the amount of flash, this results in a casting which can have "cold" defects. The "cold" defects can result in scrapped castings, rework, customer complaints and lost business.

The choice is to stop the process and repair the die and/or the machine to prevent the flash. Including one or more of the following:

Squaring the machine or repairing the platen or linkage.
"Spotting the die", Welding and resurfacing the die parting lines or faces, or slide shut off.
Welding or resurfacing of the holder block if the vents are cut too deep or are damaged.
Shimming the die inserts to create a shut off.

The above have proven to reduce flash, improve part quality and increase productivity by reducing cycle time and scrap.

If you need assistance reducing flash and improving profits, contact us by one of the following methods.

Other technical articles on die casting by Bob McClintic

For more information contact Bob McClintic @: RMcClintic@DrDieCast.com

Revised: February 2017