March 14, 2011
Aluminum is a difficult material to process as it poses a unique set of challenges, particularly when it comes to grinding. The best way to ensure that you’re grinding process is efficient while also providing you with the desired result hinges on using the correct abrasive at all times.
Aluminum is the most common metallic element in the world. In its pure form, aluminum is silvery-white and lightweight. While readily available and commonly used, aluminum is a difficult material to process as it poses a unique set of challenges, particularly when it comes to grinding. In some aluminum manufacturing applications, grinding is a required finishing process for material deburring and cleanup. The best way to ensure that you're grinding process is efficient while also providing you with the desired result hinges on using the correct abrasive at all times.
Generally, three main abrasive products are recommended for aluminum grinding applications: depressed-center wheels, fiber discs, and flap discs. Each disc, when used for its specific purpose, can give you the aluminum deburring or finishing results that you're looking for.
Depressed-center Wheels. These abrasive wheels are best-suited for deburring applications and offer the best wheel life because they have a more resilient, much harder backing than the fiber and flap discs. This backing is sturdy enough to remove an aluminum weld completely. These wheels normally contain no wax or rubber fillers, which helps impede loading on hard-to grind aluminum.
Depressed-center wheels are not recommended for finishing applications, as they would leave an obvious scratch pattern, requiring you to perform further finishing activities.
The wheels are available in ceramic alumina, zirconia alumina, and aluminum oxide abrasives.
Fiber Discs. Fiber discs offer cool cutting action for cleanup and repair applications. In general, fiber discs have a shorter lifespan than depressed-center wheels or flap discs.
Zirconia grain is recommended because it has the ability to microfracture, exposing sharp cutting points constantly, which helps to extend disc life.
Flap Discs. These discs combine the best attributes of both depressed-center wheels and fiber discs. They can deburr and perform cleanup finishing simultaneously, saving time and money.
Flap discs have three main components—backing plate, adhesive, and abrasive cloth. The abrasive cloth is layered, providing a cushioned substrate that results in high heavy stock removal rates and surface blending action.
Welders and fabricators perform grinding on aluminum for many reasons, whether it is preweld surface preparation or postweld bead finishing or removal. Compared with other metals, aluminum has a much lower melting temperature, so it melts easily.
This low melting temperature causes the material to coat the abrasive disc during grinding, covering the grit and exposing only bits of aluminum. This results in increased heat generation at the point of contact. Continued grinding produces even more heat, which produces more melting, which in turn causes the grinding operator to want to push down harder. Not only is this more labor-intensive, it results in more heat that causes loading. Longer aluminum chips coat the abrasive, which prevents the grain from doing its job.
For best results with flap discs, use light and even pressure to optimize the grinding process and reduce loading. Using a T29 (conical) disc at a 15-degree angle provides high stock removal rates and maximum surface contact, which are key when speed and aggressive grinding are needed. For applications that require a smooth finish or for surface cleaning, use a T27 (flat) disc at a flat work angle.
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