Cutting Costs with Diamond Coatings

Carbide tools with CVD diamond coatings can help manufacturers increase both productivity and product quality in machining green ceramics, making them well worth the extra investment.

After drilling more than 3000 holes, the CVD diamond coated drill was still in good condition.
Countless options exist when seeking the optimum cutting tool for green machining operations. Advanced chemical vapor deposition (CVD) diamond coatings can be used on carbide cutting tools to enhance both productivity and product quality, but many manufacturers shy away from this solution because of the high first cost of the tools. What many companies don’t realize is that the benefits obtained from CVD-diamond coated tools often far outweigh the initial investment in the technology.

When U.S. Technical Ceramics (USTC) in Morgan Hill, Calif., wanted to improve productivity and product quality in its green machining operations several years ago, it decided to test carbide tools with CVD diamond coatings from sp3, Inc. As a custom manufacturer of high-tech ceramic components, USTC is continually challenged to improve process reliability and quality while keeping costs to a minimum. According to Brian McElligott, manufacturing engineer, the CVD diamond coating appealed to him from the very beginning. “When sp3 first approached me with this new coating, I was eager to test it. The simple fact that the coating lasts so long, preventing downtime and enabling our operators to make parts instead of grind tools, convinced me that it would be worth the investment.

“I’ve never been one to look at just the first cost,” he adds. “If something’s going to last longer, I’ll take the chance. Obviously diamond is going to last longer than straight carbide. But I was also curious to see just how much it would improve the performance of our tools.”

Testing the Tools

The company began with some general experiments using coated inserts, drills and end mills to determine which type of equipment would produce the best results. Since McElligott’s goal was to prove the merit of standard available coatings in normal production situations, all of the coatings evaluated were selected from sp3’s general catalog. Based on the initial experiments, sp3 made some slight adjustments to the tools. USTC then ran some documented tests to determine the precise benefits of the CVD diamond-coated tools.

One tool tested was a 3⁄8-in. diameter, 0.030-in. radius carbide end-mill. USTC was extensively using an uncoated version of this tool to machine 99.5 and 99.9% aluminum oxide parts that it produces for a variety of customers. Using a material application code (MAC) matrix developed specifically for the coatings (see sidebar: Matching the Tool to the Application), sp3 engineers recommended that a MAC 5 standard diamond coating be applied to the tools. A summary of the test results is shown in Table 1.

The dramatic improvement in productivity demonstrates that a decision about tooling should not be made based merely on the upfront cost of the tool. In this case, a 10X improvement in productivity reduced the actual per-part cost by 300%.

Every test run continued to confirm that measured productivity was increased with a corresponding reduction in actual tool costs. Based on this information, USTC decided to switch all of its production end-mills to CVD diamond-coated mills.

With the encouraging results using the CVD diamond-coated end-mills, the company turned its attention to the many carbide inserts that it used to machine components up to 18-in. diameter. In this application, standard turning inserts were selected with a recommended MAC 17 diamond coating. The results were similar to those achieved with the coated end-mills. With 200-300% improvements in tool life and corresponding reductions in both set-up time and cycle time, the decision to change to CVD diamond-coated inserts was also easy to reach.

Maintaining Hole Size

One of the real challenges in machining ceramics is maintaining the hole size in drilling operations. “With green ceramic being so abrasive, a carbide drill will typically give you about 50-60 holes before the point wears and the pieces begin to show a taper. Every time that happens, you need to regrind,” says McElligott. “We used a diamond-coated #30 drill for one job. When we finished the job after drilling more than 3000 holes, the diamond-coated drill was still in good condition. At $70 for the drill, this was a tremendous savings in downtime alone.”

Since the coated tools don’t need to be reground as often as uncoated tools, they’ve also enabled the company to experience gains from minimized downtime.

Confirming the Savings

McElligott and his staff were willing to look past what seemed the prohibitively high individual costs of the diamond coated inserts and end-mills to determine what real production costs could be affected. By carefully testing and documenting test results, they were able to confirm that the new CVD diamond coatings could deliver real savings to the bottom line of their machine shop. Savings in tool costs, improved productivity, fewer set-ups and tool changes, and the quality of the machined surfaces made the evaluation effort pay off.

“Most of our machining operations are now running with CVD diamond tools, and we’re convinced that there are more gains to be achieved as we continue to pursue our evaluations of other diamond applications,” says McElligot.

For More Information

For more information about CVD diamond-coated tools, contact sp3, Inc., at 505 E. Evelyn Ave., Mountain View, CA 94041; (650) 966-0630 or (800) 773-9940; fax (650) 966-0633; e-mail; or visit

SIDEBAR: Overcoming Challenges in CVD Diamond Technology

The technology of growing diamond on a hard surface, such as tungsten carbide, is well established. However, a number of challenges had to be overcome before the coating could be reliably used to enhance the performance of carbide cutting tools.

The first challenge was to create sufficient adhesion or bond strength between the diamond and the carbide surface. It is not inherent that a chemically sound bond can exist between diamonds and a dissimilar material such as tungsten carbide. After considerable study and research, sp3 researchers developed patented surface preparation methods that ensure adhesion.

The second challenge was to develop a reactor that could both produce production quantities of coated material and maintain uniform consistency throughout the coating chamber. To overcome this challenge, sp3 researchers developed a state-of-the-art reactor chamber with computer-controlled cycles that provides the capacity and coating quality necessary to produce high-performance diamond coated tools.

As a result of these and other research and development efforts, CVD diamond coated tools are now becoming widely available on the commercial market.

SIDEBAR: Matching the Tool to the Application

Different CVD diamond coatings provide different machining characteristics. To make it easier to select the right diamond-coated tool for each application, sp3 developed a Material Application Code (MAC) matrix. Higher MACs represent a thicker diamond surface and a more robust tool, while lower MACs tend to have a sharper edge. For less abrasive and less brittle materials, a smoother surface finish can be achieved with a lower MAC. In general, ceramic manufacturers should use the lowest MAC that is suitable for the material being machined.

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