Tool and Cutter GRINDING

Do you get the point?

Keeping tools and cutters sharp is one of those inescapable overhead costs all manufacturers have to accept.

Like most other decisions in industry, deciding how and where to sharpen tools is a product-specific choice. It depends on overall cost, not just the rework fee.

Do-it-yourself sharpening is normally done by companies that can afford to have staff dedicated to this work or that need very specialized work.

But, overall, the trend seems to be greater use of outside sharpening specialists as manufacturers reduce labor costs. These services are frequently offered by tool manufacturers and by a large number of "regrind houses."

One company that has benefited from the trend to custom tooling is Acu-Grind Tool Works (Bradenton, FL). This operation specializes in both tool rework and the manufacture of specialized tools. Its president, Tony Antony, reports particular growth in the aerospace industry where tapered tools and tools for thin-wall cutting of aluminum are in demand.

In addition to reworking tools to custom specs the company also offers a design service to improve tool performance and life. "While this adds to up front cost, those who look at total cost per hole or cost per part will find we offer a cost advantage," according to Antony.
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According to Ed Sinkora, Walter Grinders (Fredericksburg, VA), their machines are optimized for tool grinding with a design that combines complete geometric freedom with high rigidity. "For example, with our machines, you are always grinding near the center of the work envelope. Overhang is minimal so vibration is minimized. These are patented features.

Walter's latest machine is called the Helitronic Vision, a 3D gantry design that has linear motors driving the linear axes and frameless torque motors for the rotating axes.

"We also beefed up the base, which is a 14,000-lb [6350-kg] mineral casting, to accommodate the extreme acceleration of the linear motors," he notes. (The machine weighs 20,000 lb [9071 kg].)

"Measuring the finished tool is an important issue," Sinkora says. "We use two systems. For in-process compensation, we use a probe system built into the machine that measures and adjusts diameter, flute depth, rake angle, helix angle, and back taper.

"But you can't certify a tool on the same machine on which it was made or reworked. It has to be an independent, off-line unit. We offer a machine that can measure down to ±0.7µm, proven with a NIST-certified gage.

As to market trends, Sinkora says, "The hottest new tools are those with variable helixes within the flute or helixes that vary from flute-to-flute on the same tool. Handling this work requires special programming."

Walter offers Tool Studio software to meet this need and other development challenges. It allows the user to create a grinding program while modeling the tool in 3D-the two functions are completely integrated. When you change the model, you change the program. There is no need to rewrite codes.

"Our software also contains a number of proprietary programs," Sinkora says. "We have a number of partnerships with major tool developers.

"The overall goal is achieving good surface-finish and accuracy at high speed. For example, we are able to grind and measure a K land.

Anca (Farmington Hills, MI) is a grinding machine builder specializing in tool sharpening. According to VP, Russell Riddleford, "Our company serves three markets: tool manufacturers, resharpening houses, and individual companies that have their own sharpening operations.

"Both the resharpening and individual companies are expanding, particularly those operations that can't afford a long turnaround time. You can't wait two weeks for a tool with a million-dollar machine sitting idle."

Riddleford says much of Anca's development work is aimed at improving software. "We have the dual goals of making it simpler, and handling the more complex geometries that tool designers continue to generate.

"We provide the customer 'lightsout' capability. You load the tools, set the programs, and that's it. The user need only program the tool's major parameters such as tool type [mill, drill], and key dimensions. On the other hand, these machines can be programmed for one-off capability.

"A unique feature of our machine is automated dressing. The user simply sets the frequency [every five tools, for example] and the dresser does the rest.

Measuring the reworked tool is an important aspect of the process. One example of the equipment used for this task is the Genius 3 from Zoller Inc. (Ann Arbor, MI). An automatic system that measures and inspects tools using incident and transmitted light, it magnifies the tool up to 200×. There is a measuring program for all critical parameters including radius contour, and tool contour and concentricity. It measures tools up to 600-mm long and 200 mm in diameter with repeatability of ±2µm and accuracy of 1µm.