Cracks in anodized aluminum after printing
Cracks in anodized aluminum after printing
(OP)
I have products made for me in Eastern Europe that use aluminum faceplates. We are talking plates that are about 1 by 2 inches. The former supplier for printing the plates with some text and marks in black ink has gone out of business. I have told the factory to go to a silk screen process.
The report I received today says the plates are cracking when bent 90 degrees, which is a part of the manufacturing/assembly process. The printing shop uses anodized aluminum prior to printing. This I understand is pretty common.
I have no training in metallurgy or coatings. I am a EE. My supplier in Europe is an assembly house that builds to my specs, and they have no knowledge either.
Although the reported quality of the printing is good, I can not live with plates that crack and lose strength as the end use is high vibration. Is the anodizing altering the aluminum, making it less ductile, or are we seeing only surface cracks in the coating that have no effect on the final strength of the aluminum. If so, will the cracks at the point of the bend grow, or will it be only a cosmetic issue restrained to the the single area of the bend?
The report I received today says the plates are cracking when bent 90 degrees, which is a part of the manufacturing/assembly process. The printing shop uses anodized aluminum prior to printing. This I understand is pretty common.
I have no training in metallurgy or coatings. I am a EE. My supplier in Europe is an assembly house that builds to my specs, and they have no knowledge either.
Although the reported quality of the printing is good, I can not live with plates that crack and lose strength as the end use is high vibration. Is the anodizing altering the aluminum, making it less ductile, or are we seeing only surface cracks in the coating that have no effect on the final strength of the aluminum. If so, will the cracks at the point of the bend grow, or will it be only a cosmetic issue restrained to the the single area of the bend?
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RE: Cracks in anodized aluminum after printing
Anodize is an electrochemical process that forms oxides of alumina. The ceramic is both penetrating and yields real surface growth. Hardness varies with thickness, alloy of aluminum, and temperature during formation. These coating types are NOT suited for post-forming. Fracture is inevitable. Whether the cracking is superficial and limited, a one time event, I can't say. Mostly, it will be determined by thermal and/or mechanical stresses in your environment. You may want to consider aircraft aluminum grades, like 7050 or 7075. They have great fatigue strength and are compatible with the "hard coating" processes.
For more information, consider:
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William Gunnar
http://www.IndustrialCoatingsWorld.com
RE: Cracks in anodized aluminum after printing
maybe you can change the internal radius of your part
something like 2 or 3 times the thickness