Secondary Process Purpose
Vibe Deburr Parts are vibrated through a tub filled with specially polished stone. This removes flash and loose burrs from the casting, and smoothes any sharp edges. The surface of casting has a dull luster to it once done.
Thermal Deburr Same as above, but the process is done in an oven. The casting's surface color and finish does not change significantly.
Shot Blast Shot Blasting is a process whereby the casting is blasted with steel media. This removes any surface discolorations, and light heat checking. The die cast surface ends up having an even, matt finish. The part will look cosmetically pleasing.
Machining Machining is probably the most common of all secondary operations. It is used to make a part usable in an assembly. For example, threads can be added, surfaces can be milled flat to within thousands, or large diameters can be bored to add seal rings or gears in them. Machining and casting are integral to the manufacture of aluminum components in practically any industry that uses cast aluminum parts.
Broaching A spline is a feature that gets commonly broached in a die casting.
Powder Coating Adds color - practically any color is possible.
Anodize Adds corrosion resistance to a part so that it can survive salt or corrosive atmospheres. This process can also be used to improve surface hardness, allow dyeing, improve lubrication, or improve adhesion. Specifically, the process increases the thickness of the oxide layer on the surfaces of metals, including aluminum alloys. The particular anodize process and/or color to be used is typically specified on the print as a MIL specification.
Chemical Film / Yellow Chromate Chemical Film, or chromate conversion, produces very similar results to anodizing in an aluminum casting, however, whereas anodizing simply increases the thickness of the oxide layer on a metal, chemical film adds a chromate conversion film that minimizes surface oxidation, corrosion, and allows for improved adhesion and painting.
Plating Plating can be added to a part after it is polished. Plating tends to be much more economical in zinc than in aluminum. Plating can add a deep, lustrous mirror finish to a casting. For example die castings are commonly platted with a chrome, or nickel finish.
Impregnation Impregnation is a common process used to make die castings pressure tight. It is commonly performed in a vacuum. The process impregnates the die casting with a polymer resin that seeps into any micro cracks or micro porosity present in the casting and seals them. Depending on the pressure requirements, multiple impregnations may be needed.
Heat Treatment Heat treating is usually done to increase the hardness, and therefore the UTS of a casting. Heat treatment is a tricky process in die casting since it may expose internal defects such as porosity, as evidenced by blistering. High pressure die castings can be treated up to a T5 with little complications. High Pressure die castings are very difficult to heat treat to a T6.