Wolfram Manufacturing
Wolfram Manufacturing in Austin, Tex., machines complex geometries on four- and five-axis CNC machines.

Abrasive Tool Cuts Cycle and Finishing Times

Sept. 15, 2017
Versatile flexible hone performs fine surface finishing for internal bores, edge-breaking for undercuts, deburring for intersecting drilled holes.

For contract part manufacturers, the ability to produce tight tolerance parts more quickly is critical to profitability in a crowded, competitive market. To do this, machine shops are always looking for creative ways to improve overall cycle time, including speeding metal finishing operations. Although shops may have some auxiliary finishing equipment, their first focus is machining. As a result, many shops send out machined parts for secondary finishing at secondary processors that offer services like thermal deburring, tumbling and burnishing.

However, for job shops like Wolfram Manufacturing in Austin, Tex., which machines metal parts with complex geometries on four- and five-axis CNC 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 orders to their customers.

“There’s the additional time — not to mention the additional cost — of having someone else do the work. In the competitive environment today, we’re often faced with short lead times from customers,” said Tim Urano, quality manager. “Having to send parts to an outside vendor eats into our lead time and takes significant planning.”

Urano described a better alternative for many machine shops: incorporate machine tools that can complete the finishing tasks within the scheduled machining process.

“Any time we can incorporate secondary operations right into the machining process, we save time and money, and reduce our work in progress,” he added.

For example, Wolfram Manufacturing took an order to produce a unique part for a sliding valve assembly with complex internal geometries that require a high surface finish on the internal bore, and the elimination of any sharp edges from drilled holes. Sliding valves are movable elements in a system; they are incorporated into the design in order to direct the flow of a working fluid into the proper channel. In this specific project, the assembly functions as part of a larger product used in pressurized down-hole drilling tool.

To operate properly, the valves use 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,” Tim Urano emphasized. “It is one of the main reasons we use the Flex-Hone tool.”

Brush Research Manufacturing’s Flex-Hone is a highly specialized abrasive tool characterized by the small, abrasive globules that are permanently mounted to flexible filaments. It’s available in many sizes, abrasive types and grits, and the tool can be used for deburring, edge-blending, cross-hatching, and removing cut, torn or folded metal.

“It’s very easy to put the flexible hone into 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 or five axis paths to be effective,” explained Urano.

To satisfy its customer’s requirements, Wolfram Manufacturing 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,” said Urano. “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 multi-step process, Wolfram Manufacturing uses 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 they 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 often are used with automated production equipment, they also can be used for offline deburring. If during post-processing or inspection any damage occurs to the bore finish, Wolfram is able to go back in and clean it up with the hone.

Urano added 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.”

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