Precision Stamping Co.
The deep-drawn part has two stepped sections, and was specified to include a hole in each section, leaving a heavy burr.

Deburring Piercings with a Customized Flexible Hone

Oct. 25, 2017
Deep-draw stamping operation finds a customized in-house solution to the problem of burs obstructing tight-tolerance holes

For metal stamping operations, the very nature of the shearing process that creates intricate, tight-tolerance piercings inevitably creates burrs requiring a secondary finishing step to remove them.  This is particularly true for parts with wall thicknesses in excess of 0.005 inches, which often results in heavier burrs. As a result, the operators must decide how to remove the burrs most efficiently. 

For many stamping operations, this means manually deburring each part, an in-house undertaking, however finishing, smoothing, and removing burrs by hand not only significantly increases manufacturing time but also is prohibitive in terms of labor costs and employee ergonomics.  For large production runs, this option is even less viable.

Another alternative is to send out the stamped parts for a secondary finishing step, such as thermal deburring or tumbling. These techniques effectively remove excess material, but this sequence increases the time to ship and return the parts. It also adds to the production cost. 

Not incidentally, both techniques are known to mar the surface of the part.

For Jesse Parke of Precision Stamping Co. of Howell, Mich., a company that specializes in deep-drawn parts, the dilemma left him with only one alternative: find a more efficient and inexpensive method to complete the deburring work in-house.

Precision Stamping specializes in deep-drawn metal parts for automotive, industrial, and military parts providers worldwide. The 71-year-old company, among the largest of its kind in the Midwest, primarily produces parts like oil-cooler lines and quick disconnects. According to Parke, a third-generation stamping engineer, Precision Stamping can pierce holes in sheet metal blanks and formed shells using complex machinery and set-ups that are “flirting on the edge of what’s possible and what’s wishful thinking.”

However, the production of hundreds of thousands of stamped parts with tight tolerances and intricate piercings – as low as 0.078 inches on one recent job – still creates challenges in deburring.

Parke pointed to one recent part, a spring cup that required a novel solution.  Like many deep-drawn parts, it was flared at the top with a narrower diameter for the body.  The part specification included piercing a hole in each of the “stepped” sections, leaving a heavy burr.   

To resolve the problem, Precision Stamping initially opted to send the parts for thermal deburring, a process that removes the excess material by vaporizing and burning it off.  However, this step involved additional time, vendor expense, shipping expense, and often required cleaning off black carbon residue once the parts were returned to the shop.

Eager for a more efficient alternative, Parke began to explore and research options to keep the parts (and the deburring work) in-house.  Although initially he was unable to find a viable option, in 2015 at a trade show, a colleague recommended the Flex-Hone from Brush Research Manufacturing

The self-centering, self-aligning, and self-compensating Flex-Hone features abrasive "globules" attached to flexible filaments along a central shaft and can be used in any rotating spindle. Commonly known as the ball hone, the Flex-Hone is used in CNC machining for deburring and surface finishing of metal parts with cylindrical bores or through-holes.  Although it is often used with automated equipment, the abrasive tool also can be used with a drill.

The product is distributed worldwide and available in a range of sizes, abrasives and grits.  However, for the Precision Stamping application, none of the standard options would work for the spring cup, due to its two-stepped design.

So, Parke contacted BRM and explained to the engineering solutions team that this job required a “stepped” hone that would work with the specific dimensions of the part. “With the part being stepped, I was not sure if we would need a custom brush or what the ideal choice would be,” Parke explained. 

BRM is a developer and manufacturer, and it has the insights and resources to customized hones for unique applications.  This may include custom sizes – from extremely large diameter to miniature – as well as unique configurations, such as tapered or stepped.  According the Parke, the developers responded quickly with a tool that met Precision Stamping’s need. 

Now, after the parts are stamped and cleaned, they are transferred to a nest for piercing.  When that is completed, they are moved to another nest, where a stepped Flex-Hone is inserted and rotated using an automated pneumatic drill.  The same operation is repeated in the opposite direction to ensure maximum deburring as well as maximize brush life.  The part then drops through an escapement in the machine as finished goods.

Since Precision Stamping started using the custom Flex-Hone, Parke said they have experienced a steady increase in production output.  In one six-hour period, operators were able to run 8,000 pieces and not a single part needed additional deburring. “The Flex-Hone is definitely helping us keep costs down by not having to send parts out for thermal deburring,” he said. “If you don’t have to do that, you’ve saved all the part-handling time and saved all that money.”

Parke said that, all told, the improvements have been significant. “Now we can deburr in-house and they look ten times better than what we were getting before after the thermal deburring.”

Because the jobs that come to Precision Stamping are more complex, technically demanding projects (manufacturers typically commission off-shore suppliers for the simpler, open-tolerance jobs), Parke said he expects to use custom Flex-Hones for future customers’ jobs, too: “I see that only increasing as we match the correct Flex-Hones with the correct tooling.”

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