An article from PRODUCT FINISHING magazine
A process for preparing OEM and aftermarket aluminum wheels for chrome plating is saving platers and polishers up to $20 per wheel. The process is a simplified drag polisher that pushes four wheels face first through a circular tub of specially designed grinding media (see Fig. 1, 2 and 3). Polishing with media allows for a more controlled and consistent grind that does not cut into the porosity layer below the surface. The process of impacting media against the surface of the wheel causes surface micro-porosity to collapse, significantly eliminating plating rejects. The maintenance of the machine is minimal, and multiple machines can be set up for the price of one standard automated machine with much more capacity.
As can be seen in Table I, the Spin Polisher TM, manufactured by La Habra
Welding (Bell Gardens, CA) has significant advantages over standard processes.
This initial capital cost is low for automated equipment, yet the hourly
production rate is similar, The process can accomplish approximately 80% of the
raw aluminum, >90% of the copper polishing and >90% of stripped wheel
polishing, significantly reducing the reject rate for poorly polished wheels and
blistering. These estimates are for standard wheel geometries cast via gravity
or low-pressure processes.
The total average polishing costs per wheel can be reduced by approximately 75%.
This savings is much greater than the
savings per wheel achieved by the other polishing systems. As seen in Table 1
,both the aluminum and copper polishing costs are reduced significantly. The
cost of poor quality, which includes rejects due to polishing mistakes and
plating rejects due to embedded compound and porosity is reduced. The aluminum
wheels need minor touchup prior to replating. Dayton Alloy Wheel, LLC, is using
the system for polishing its copper plated-wheels after a three-year evaluation
of the process.
Wheels that have been stripped undergo almost the same polishing intensity as
raw castings. Cutting into the aluminum at this stage causes more problems than
with a new casting and generates a high level of rejects after polishing.
Because more micro-porosity has been exposed, stripped wheels also have higher
reject rates during the plating operation. Typically, about 5O% of wheels that
are stripped end up rejected either after repolishing or replating. With this
new drag style process, stripped wheels can be polished quickly
"I use the system to polish all nickel replates, all fully stripped wheels,
most copper-plated wheels and most raw casting. The wheels require little
touchup and there are few rejects," commented Duane Rogers, plant manager
for Perfection Plating (Banning, CA).
The four head assembly is driven by one motor and gearbox and has no racetrack assembly. The wheel rotation is induced without the aid of a motor. This significantly reduces the initial capital costs and ongoing maintenance costs. Loading and unloading only four wheels per cycle reduces the average wait time per wheel, increasing throughput. As with the racetrack polisher, force grinding by pushing media around and through a wheel is not as geometry sensitive as other automatic grinding processes. Most wheels can be run under the same operating conditions, and the machine can handle 14-22 inch-diameter parts. One operator can run multiple machines.
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