Cutting Tool Engineering
June 2011 / Volume 63 / Issue 6

Finely finished flutes

By CTE Staff

ctem6.tif
Courtesy of Form Tool Technology

When Form Tool Technology replaced manual polishing of drill flutes with a CNC polishing process using Trizact diamond polishing wheels from 3M, the shop was able to save time, maximize consistency of results and incorporate tool polishing in its lights-out production strategies.

When manufacturing and reconditioning round cutting tools, Form Tool Technology Inc., Elgin, S.C., blends advanced technology with customer-focused responsiveness. Describing the company founded by his parents 41 years ago, President Michael Robbins said: “We see ourselves as a state-of-the-art, high-tech company living within a service-oriented culture. We don’t have to go through 12 different engineers to get a change made. We are flexible with our customers, and they recognize that.”

Form Tool Technology regrinds round tools and makes some standard endmills and drills, but primarily produces specials at its facilities in South Carolina and York, Pa. “Our main focus is meeting tolerances within 10µm in diameter and length,” Robbins said, adding that diameters range from 2mm to 32mm.

The nature of custom toolmaking dictates varying production volumes. “Some jobs are six pieces, some are 600,” Robbins said. Typical turnaround for a special is 2 to 4 weeks, but, in some cases, the company reduces that to a few days when a customer needs the tools to maintain production. Unattended machining helps facilitate a quick response to customer needs. “We do a lot of lights-out grinding,” Robbins said. “We have robotics incorporated on our machines, and we set up pallets of tools at night to run unattended.”

One example of the toolmaker’s continual efforts to fulfill specific customer needs is its flute polishing capabilities. About 5 years ago, the company began polishing drill flutes to enhance chip evacuation. “Some of our customers are drilling aluminum, which is gummy and has a tendency to adhere to the carbide,” Robbins said. “By having a better finish on the flutes, chips don’t seem to stick quite as much on the face of the tool.” He added that polishing can enhance adherence of tool coatings, and a polished surface is more aesthetically pleasing than an unpolished one.

Initially, the shop polished tools manually. “We bought a sheet of shoe leather, put it through a process to harden it and cut it into the shape of a grinding wheel,” he said. “We mounted the wheel on a manual grinding machine, put a lapping compound on it and ran the flutes of the tool through the wheel.”

An operator fed the drill in and out of the wheel by hand. The process was labor- and time-intensive, and the manual feed did not produce consistent results.

Looking to streamline the process and make it more predictable, Form Tool Technology met with representatives of 3M Abrasive Systems Div., St. Paul, Minn., and asked for a way to “get the process out of the hands of an operator and let the machine take care of it,” Robbins said.

At the time, 3M was developing a polishing technology intended to improve tool performance for end users and at the same time provide toolmakers a more cost-effective way to polish tool features. Mike Harrington, 3M superabrasive sales specialist, said Form Tool Technology provided real-world feedback on wheel performance as 3M developed the wheels.

The development effort focused on finding an alternative to traditional diamond polishing wheels, which feature fine-grain diamond abrasive in a rigid resin matrix. According to Harrington, the fine-grain bonded wheels “do work, but are difficult to apply. They are extremely hard and can cause microchipping and burn.” He pointed out that a rigid polishing wheel has to match the flutes perfectly—within microns—to polish effectively, and “that’s hard to control.”

The solution was a new diamond wheel that combines performance characteristics of resin-bonded diamond wheels with those of nonwoven abrasive wheels. Unlike fine-grain diamond wheels, the new polishing wheels, marketed as 3M Trizact diamond polishing wheels, “have some forgiveness,” Harrington said, and can polish effectively while still possessing enough rigidity to be trued and dressed to follow complex tool geometry. Fresh 10µm diamond material, dispersed throughout the wheel, is continually exposed as a wheel wears, 3M reports.

Harrington added that the wheels enable polishing not only of tool flutes but also of primary relief angles and other features.

Both the wheels used to grind the flute contours and the polishing wheels can be mounted in wheel packs in a CNC machine, eliminating the need to polish manually. Troy Heuermann, business development manager for the 3M Abrasive Systems, said before the new wheels were available, “there hadn’t been a real, sustainable, automation-capable method of producing a polished finish, especially in the flute area of an endmill or a drill.” According to Heuermann, the free-cutting wheels also minimize the heat produced when polishing.

Use of the wheels enables Form Tool Technology to include polishing in its lights-out production strategies. “We grind flutes in the tool and then come back with the polishing wheel,” Robbins said.

Application of the wheels is typical of the company’s ongoing improvement efforts. Robbins said, “Right now, for instance, we are looking to incorporate a robot in our inspection department. So instead of doing statistical batch inspection, we can do 100 percent inspection. We always have a hot list of items that we consider for continuous improvement.”

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