Shops like Wolfram Manufacturing Inc. (Austin, TX) rely on Flex-Hone abrasive tools from Brush Research Manufacturing (Los Angeles) to provide fine surface finishes on CNC machined parts. The abrasive tools are inserted into the toolholder and programmed with a simple toolpath to process internal bores, along with edge breaking of undercuts and deburring of intersecting drilled holes.
To produce tight tolerance parts at a faster rate and remain profitable in a highly competitive market, machine shops constantly look for creative ways to improve on overall cycle time, including speeding metal finishing operations. Although machine shops may have some auxiliary finishing equipment, their primary focus is on machining. As a result, many shops must send parts out for secondary finishing steps such as thermal deburring, tumbling, and burnishing.
However, for job shops like Wolfram, a company that machines metal parts with complex geometries on four and five-axis machines, sending out parts for secondary finishing not only adds to the cost, but can impact quality and increase the time it takes to deliver the parts to customers.
“There’s the additional time, not to mention the additional cost of having someone else do the work,” said Tim Urano, Wolfram quality manager. “In the competitive environment today, we’re often faced with short lead times from customers. Having to send parts to an outside vendor eats into our lead time and takes significant planning.”
A better alternative for many machine shops is to incorporate machine tools that can complete the finishing tasks within the machining process. “Anytime we can incorporate secondary operations in the machining process, we save time, money, and reduce our work in progress,” said Urano.
In one example, Wolfram was charged with making a unique part for a sliding valve assembly with complex internal geometries that required a high surface finish on the internal bore and the elimination of any sharp edges from drilled holes. Sliding valves, which are movable elements in a system, are used to direct the flow of a working fluid into the proper channel. The assembly is part of a larger product used in pressurized downhole drilling tools.
To operate properly, the valves utilize O-rings that must be seated properly and maintain tight contact with the bore without getting cut by any sharp edges from intersecting holes or undercuts. “The customer’s primary concern is that the O-ring seal is protected from being cut or damaged by any sharp edges or burrs,” said Urano. “It is one of the main reasons we use the Flex-Hone tool.”
The Flex-Hone from Brush Research is a highly specialized abrasive tool characterized by the small, abrasive globules permanently mounted to flexible filaments. Available in many sizes, abrasive types, and grits, the tool is used for deburring, edge-blending, cross-hatching, and removing cut, torn, or folded metal.
“It’s very easy to put the flexible hone in a toolholder, give it a simple toolpath cycle and let it run. With some of the other in-machine deburring tools, it can take complex four to five-axis complex paths to be effective,” explained Urano.
To satisfy the customer’s requirements, Wolfram had to reliably remove burrs and sharp edges in cross-drilled holes and other difficult-to-access areas, such as undercuts. “The part has some undercuts and some intersecting cross-holes, so we use the tool to edge break and help blend the chamfers at the same time,” he explained. “The hone is one of the only tools that can reach that edge. It doesn’t alter the feature geometry, but it rounds it enough that it won’t damage the O-ring.”
A high surface finish is called out on the internal bores where the valve assembly actuates. As part of a multistep process, Wolfram utilizes a coarse grit Flex-Hone to smooth out any irregularities left during drilling and finishes the bore with a fine grit hone. “Final finishing operations don’t accommodate much variation, so we need the uniform surface preparation that the flexible hone provides,” explained Urano. “By using these tools, we can achieve more consistent results.”
While Flex-Hones are often used with automated production equipment, they can also be used for offline deburring. If any damage occurs to the bore finish during postprocessing or inspection, Wolfram is able to go back in with the hone and clean it up.
Urano concluded that Wolfram Manufacturing will continue to use the brush: “Whenever we see applications with intersecting holes or particular surface finishing requirements in a bore, it’s one of the first tools we will go to.”