Wheels that incorporate abrasive grains tackle buffing applications using less compound.
Above: A Norton FAB wheel buffs a rotor blade to impart a lustrous surface finish.
November, 2023-Abrasive buffing compounds are effective for imparting mirror-like, lustrous surface finishes on various metal parts, as well as preparing surfaces for plating, painting or other coatings. The conventional buffing process using a compound, buffing wheel, compound applicator, buffing machine and operator or robot, however, can be a difficult-to-control process in which compound is splashed onto surrounding equipment and work areas.
“The cleanup from buffing compound can be pretty intense and time-consuming and, of course, if it’s a waste, there’s a cost to dispose of it,” says Anne Bonner, senior product manager of Norton | Saint-Gobain Abrasives in Worcester, Massachusetts.
According to the ASM Surface Engineering Handbook, “Polishing and buffing compounds are difficult to remove because the soil they deposit is composed of burned-on grease, metallic soaps, waxes and vehicles that are contaminated with fine particles of metal and abrasive.”
Uniform dispersion of abrasives on Norton FAB buff wheels provides a consistent buffing performance.
The fixed abrasive grains of the FAB buff wheels do the job typically performed by buffi ng compound. Less compound reduces clean-up, maintenance and waste
To achieve a specified surface finish while cutting the amount of buffing compound needed by half to 90 percent Saint-Gobain Abrasives introduced the Norton FAB (Fixed Abrasive Buff ) buffing wheels. With fixed silicon- carbide abrasive grain on both sides of the waterproof and tear-resistant, non-woven nylon cloth backing, the company reports the buffing wheels last 35 percent longer than traditional cotton buffs. This resuls in fewer buff changes and more parts completed per buff . In addition, FAB wheels are less likely to snag and tear when encountering sharp edges, compared to cotton buffs.
FAB buff wheels last about 35 percent longer than traditional cotton buffs.
KEEPING COOL
Some buffing compound is usually needed to help cool the part surface, Bonner says. “You don’t want to overheat the part since it’s nearing its final form. You use a little bit of compound or, in some cases, just water, depending on the specifics of the application, just to keep that temperature under control.”
Excessive heat the enemy of the buffing wheel and abrasive finishing processes can discolor metals, reduce abrasive product life and even start fires, according to the company.
Bonner adds that the petroleum or fatty acid component in compounds tends to be flammable. “So, the less of the compound that you use, the less flammable material you have in your shop.”
With less compound being used when buffing with FAB wheels, worker safety improves because less potentially hazardous material is becoming airborne, according to the company. When some of the abrasive compound becomes airborne, it turns to dust and workers without respirators can breathe in the compound dust, which contains silica, minerals and binders.
Because the FAB wheels are for polishing applications, Bonner explains that the company uses an abrasive that is tightly controlled as far as its shape and particle size distribution are concerned. The result is a consistent surface finish with no stray scratches or random defects. “It’s a hard mineral [silicon carbide], so it works on a variety of workpiece types.”
Saint-Gobain Abrasives reports that FAB wheels are effective on hard alloys, as well as relatively soft metals such as brass and aluminum, including aluminum fixtures and automotive components. Bonner describes the process when using the FAB wheels as cut buffing in which material movement occurs. “It’s not a color buff where you have the high polish. That’s a little bit finer on the scale. We usually say a single- digit microinch Ra can be imparted by the fixed abrasive buff .”
FAB wheels impart high luster and consistent finishes in a 1 to 5 μin. Ra range from a coarse 280-grit prepped surface, the company reports. The ability to produce a mirror polish on workpieces with coarser prepped surface finishes can eliminate several finishing steps, which provides additional cost savings.
WALK, DON’T RUN
Using the FAB wheels on semi-automatic or robotic equipment is beneficial, Bonner explains, because they usually have variable- speed drives, which allows more control over the buffing process. “We like to reduce the speed when the FAB wheel is used versus a regular cotton buff and you’re able to do that more easily with the semi-automatic and robotic applications.”
The recommended speed that a FAB wheel should run at is 2,500 to 3,500 surface feet per minute, depending on the machine and application, Bonner says. A cotton buff, on the other hand, typically runs at about twice as fast. Running at a lower speed allows the workpiece to mush, or push, deeper into the buff , which engages more of the fixed abrasive particles with the metal surface.
In addition, a slower buffing speed will not generate as much heat in the part compared to a faster speed, Bonner notes. “It’s going to help prolong the life of the buff as well.”
FINER SURFACES
She says fabricators’ interest in buffing ever-finer surface finishes is only growing for both aesthetic and operational advantages such as reducing drag and improving flow characteristics, which can enhance the performance of impellers and other components in pumps and valves, for instance. Bearings, gears and other mechanical equipment with contact surfaces can also benefit from the reduced friction of buffed surfaces. “The better the surface finish, the quieter the operation and the less heat generation.”
Standard Norton FAB wheels are available in outer diameter sizes from 5.5 in. to 22 in. and the ply, or number of cloth layers of buff , are 12 or 16, and the pack, or waviness of the buff face, is two or four. In addition, users can request special sizes and/or additional pack and ply configurations.
Bonner says one product won’t suit everyone’s requirements perfectly. “Every polishing process is a little bit different, so having a range of options to choose from in order to reach the surface finish that is required for the application is a distinct benefit. Whether it be an engineered abrasive belt or a buff or a non-woven product that’s used, we have different options to reach the required surface finish in a reasonable cycle time for a wide range of workpieces.”
Norton | Saint-Gobain Abrasives, 508/795-5000, http://nortonabrasives.com/
