April 2011 / Volume 63 / Issue 4|
Automated surface finishing is a 'game changer'
By CTE Staff
Some manual surface finishing operations can cause operator discomfort, fatigue and injury that shrink productivity and compromise product quality.
In the case of RCBS, Oroville, Calif., concerns about just such a scenario resulted in a goal to eliminate a manual finishing operation. It also led to an estimated 60 to 70 percent increase in productivity and a substantial quality improvement.
Courtesy of RCBS
RCBS has been a leading producer of ammunition reloading equipment for more 60 years. Among its products are steel and carbide reloading dies for rifle and handgun ammunition, which are produced in high volumes, according to engineer Tim Taylor.
The die production process involved extensive manual labor to finish bores. Workers wrapped emery cloth on rods and polished the internal die surfaces, which imparted inconsistent surface finishes, according to Taylor. “That resulted mainly from ergonomic factors,” he said. “So achieving a consistent, high-quality surface finish and avoiding worker discomfort in the finishing operation became high priorities.”
RCBS explored process improvements including CNC equipment and various finishing tools. A possible solution surfaced at a trade show in the form of flexible ball-style hones that could be tailored to meet the die bore surface finish requirements and worked with RCBS’s recently acquired CNC equipment.
Supplied by Brush Research Manufacturing Co. Inc., Los Angeles, the Flex-Hone tools consist of a shaft from which nylon filaments with abrasive grit extend. The tools are available in many diameters, abrasive materials and grit sizes, and are suitable for various surface finishing and deburring applications.
“We decided to test the Flex-Hone on steel dies,” Taylor said. “Brush Research gave us some recommendations and basic guidelines. Using a spare CNC mill, we tried different speeds and feeds until we were able to consistently achieve the desired results.”
The toolmaker helped by developing a series of brushes that enabled RCBS to apply progressively finer silicon-carbide abrasives to meet its stringent surface finish requirements. According to Taylor, the steel dies come off turning machines with a suboptimal finish, which the brush honing operation improves by a factor of eight to a submicron finish. “Depending on the die, we use multiple hone sizes as well as varying grit sizes and number of strokes,” he said.
With steel die finishing automated, RCBS successfully migrated the brush honing process to its carbide dies using tools with a diamond abrasive. Then Taylor set about optimizing both processes by writing a CNC program that selects the correct brush and process parameters based on operator input about bore length, ID and other elements.
“The new automated process is a real game changer,” Taylor said. “It is probably 60 to 70 percent more efficient than the manual process, and it resulted in a substantial increase in quality. But the ergonomic improvement alone—eliminating the potential for operator discomfort and injury—would have been enough to justify the new process.” CTE
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