Aluminum is an incredibly versatile material that’s used in innumerable fabrication applications. Designers take advantage
of its light weight, strength and corrosion resistance as well as its strength-to-weight ratio. Manufacturers in the aerospace, marine and automotive markets rely on it for their increasingly fuel-efficient, lightweight designs.
But aluminum isn’t always the easiest material to work with – it’s a soft metal with a low melting temperature. The biggest frustration when cutting or grinding aluminum is loading. The buildup of melted aluminum sticks to the cutting grains and builds to the point where the abrasive stops cutting.
“As you feel the wheel not cutting, the typical response is to press harder to make it cut,” says Ben Lampi, product manager for Weiler Abrasives Group. “This actually makes the loading problem worse because you are generating more and more heat the harder you press on it.”
Understandably, the extra pressure on the material puts extra stress on the operator. Operators are constantly performing pre-weld surface preparation, post-weld finishing and material removal and are always looking for new ways to overcome the challenges that come with aluminum, including loading as well as contamination.
“There are special weld parameters you need to use with aluminum,” Lampi says. “You need to make sure the surface of the workpiece is very clean before welding. It tends to draw contaminants into the weld if you don’t clean the surface correctly. Also, you need to use the right products to cut and grind to prevent contamination.”
Overcoming Obstacles
Clearly, the best way to ensure that cutting and grinding is done efficiently while producing the desired finish is to use the correct abrasive. This means understanding the abrasive characteristics that are best suited for aluminum.
Weiler Abrasives Group designed its new Tiger Aluminum series of grinding, cutting and combo wheels with these characteristics in mind. To prevent the aluminum material from building up between the grains, the bonding on the wheels has a special formulation that allows the grains to work without loading.
The abrasives are made from a unique mix of grains and bonders. The grains were chosen for their hardness and ability to maintain sharpness and, when used in tandem with the aluminum oxide, provide a high cut rate. The bond includes additives to aid in lubrication and avoid loading, allowing for a harder wheel and longer life.
“You still get a fast cut, but you also get long wheel life because we balanced the bond structure so the wheel doesn’t load and you can use it longer,” Lampi says.
Contamination being a big concern with welding aluminum, the Tiger wheels are contaminant free. Unlike typical cutting and grinding wheels, contaminant-free wheels have less than 0.1 percent iron, sulfur and chlorine.
If a contaminant-free wheel isn’t used, the contaminants transfer to the surface of the material and secondary operations are required to clean the surface before welding. Generally, contaminate-free wheels can have reduced life when grinding on certain materials.
“Weiler has developed a way to remove those contaminants but still keep the bond very hard to give the wheel a long life,” Lampi says.
Flap and Fiber
Hard bonded cutting and grinding wheels are great for removing material quickly but tend to leave a coarse finish. For a finer finish, many users turn to a coated abrasive.
“You can start with a bonded (hard) wheel and then if you need a finer finish than what the bonded wheel can give you, move into a coated abrasive, such as on a flap disc or resin fiber disc,” Lampi says.
With the flap disc or resin fiber disc, the user can select the grit that fits the application, which provides more flexibility for those finer finishes, Lampi adds.
But the same challenges with aluminum remain. Loading is just as prevalent with coated abrasives as bonded abrasives. And contamination problems occur the same way if a contaminant-free disc isn’t used.
To prevent loading, it is a common practice to apply a wax or paste to the surface of a flap disc or resin fiber disc or treat the workpiece material with a lubricant, such as WD-40. Both practices can add contamination to the surface, requiring secondary operations to clean it up. In the long run, this practice is extremely time- consuming and costly.
Therefore, Weiler recommends the Saber Tooth flap disc, which is contaminant free, but also has a top coat applied to the coated abrasive that acts as a lubricant. The top coat helps to decrease the heat generated during grinding and to avoid loading so material does not build up between the grains.
“Flap discs without that top coat are subject to loading,” Lampi says. “Users end up throwing away the disc as soon as it loads because it doesn’t cut anymore, but there is still a lot of material left in that disc.”
Weiler’s Tiger Aluminum resin fiber discs, developed specifically for aluminum, also have a special coating that prevents loading. Resin fiber discs are used in many finishing applications because they are economical, low-cost per piece and provide a great finish.
They have the added benefit of the user being able to customize the feel of the disc by changing the backing pad to a harder or softer one.
It is important to remember that several options are available to reduce cost and maximize productivity when working with aluminum. For specific challenges, companies should reach out to their welding distributor or an abrasives manufacturer for help and guidance.
By choosing to use aluminum-specific products, operators can avoid the issues associated with heat buildup, loading and contamination. These products are ready to use right out of the box, avoiding costly cleaning and secondary operations. This, in turn, makes the process more efficient and business more profitable.
