It doesn't do a parts manufacturer any good to apply cutting tools that vary in tolerances when machining parts that require some of the tightest tolerances.

Miltera Machining Research Corp. is one such manufacturer that struggled with tolerances on the endmills it was using to produce components with tolerances as tight as 2 to 4 µm (0.00008" to 0.00016"), said Michael Blackburn, president of the Cambridge, Ontario, company.

"Then we even go beyond that to the submicron level when talking about surface finishes," he said.

Formed in 2007, the corporation employs 15 and specializes in prototyping and short-run production of complex components made of difficult-to-machine materials that typically need five-axis milling, multiaxis turning, grinding or electrical discharge machining.

Frustrated by the varying accuracy of its endmills, Blackburn said the company sought a solution.

"If you are fighting with finishes and dealing with issues on a part where you are chasing 2, 3, 4 microns, and then you are using cutting tools that have a 10-micron (0.00039") tolerance, you are chasing your tail," he said.

The business determined that it needed to produce endmills in-house to have the required extreme-tolerance tools, often with unique geometries, and searched for a suitable five-axis CNC tool grinding machine.

"Most companies said, 'What you are doing is crazy and weird, and we're not interested in helping you with that,'" Blackburn said.

The tool grinding area at Miltera Machining Research includes Anca MX7 Linear grinders. Image courtesy of Miltera Machining Research

One machine tool builder that was interested was Anca Inc. in Wixom, Michigan. He said the manufacturer was willing to help produce unconventional cutters, and the open architecture of Anca's control enabled Miltera Machining Research to integrate with the control and have direct access to the core functionality of a grinder.

"That really made the difference for us," Blackburn said, adding that his company has written software to control its grinders.

In addition, he said Anca offers grinding machines with linear motors, which enable a high level of accuracy. He noted that Miltera Machining Research has linear motors on its five-axis machines.

"A big attraction was just the ability of the machine to be stable and react in the way we would expect," Blackburn said. "In comparing some of the other machines, we weren't necessarily seeing that we get that same response."

He said the design of Anca's grinders allows Miltera Machining Research to modify machines, such as inspection systems, to suit its requirements.

"We integrate directly with the Anca machines to do dynamic feedback of the measured features and adjust accordingly," Blackburn said.

Miltera Machining Research began by purchasing an MX7 Linear grinder and now has three. He said the MX7 enables production of endmills from 0.397 to about 25.4 mm (0.0156" to 1") in diameter.

"You can get dedicated machines for small tools," Blackburn said, "but we wanted to get up to larger tools, as well as cover the whole range we need."

In addition to its own needs, he said the company determined that some of its customers required extreme-tolerance and application-specific cutting tools, so it decided to produce tools for clients as well. As a result, Miltera Machining Research makes custom cutters that Cambridge-based Zedaro Inc. sells to manufacturers serving the motor sports, aerospace, medical, consumer electronics and moldmaking industries.

Blackburn said during peak production, Miltera Machining Research manufactures about 12,000 cutters monthly, with roughly 10% to 20% for in-house applications.

"We do produce other types of cutting tools and ground components," he said, "but the vast majority is solid-carbide endmills."

Besides offering endmills with extremely tight tolerances, company tools are balanced and typically made for specific applications. One example is an endmill with a particular width for slotting.

"We make the exact size of tool you need for that geometry," Blackburn said.

He said Miltera Machining Research's specials also have unique geometries, such as custom forms, circle segments and barrel shapes.

Although the cutters can be outsourced for coating, Blackburn said most are not. Instead, they are processed internally with specific edge control and polishing. He said tool coating is an uncontrolled process that results in varying thicknesses over the substrate.

"It can really mess up a tight-tolerance tool," he said.

In addition to in-process inspection, the company has postproduction inspection devices, including a Zoller »genius« universal measuring machine, a Zoller »pomBasic« inspection machine, a Walter Helicheck measuring machine and an Alicona µCMM optical coordinate measuring machine, which enables submicron inspection of the cutting edge radius and surface finish.

Blackburn cautions, however, that producing these tools is not for the faint of heart.

"Designing tools properly is not a simple process and requires expertise in that field," he said. "We have done quite a lot of tooling research and tested many tools."