Top Tool

Posted by Dave Kari, Director of Wire EDM

"Begin with the end in mind” is the central theme in why work holding deserves early, high-priority consideration when it comes to wire EDMing complex micro parts.

The wire – especially a .00078in. wire – gets all the attention. But how to firmly (yet delicately) hold a micro part is one of the biggest challenges that can come between a high-precision, highly complex design and a small-wire EDM center uniquely qualified to cut the part. If realizing the designer’s intent is what points to wire EDMing as the micromanufacturing solution, then work holding often is where everything must begin. It’s the first place to get creative and inventive whenever an elegantly engineered micro part comes through the door.

In this case, that means getting creative about a part management concept (the fixture) sufficient to hold a component with a footprint smaller than 1mm. The part specification can also include multiple, complex features down to 100µm. And tolerances as tight as tight as 13µm, or one-sixth the thickness of notebook paper.

Equally important when it comes to wire EDMing complex micro parts, especially for use in an application like an implantable medical device, the material can be ultrathin. Whether the stock is Platinum Iridium, MP35N, or Nitinol.

Ultrathin is a relative term because it tends to be defined as the leanest dimension at which a wire EDM manufacturer can cut metal precisely. Not long ago, 0.01in. was the smallest dimension for something labeled ultrathin. Then 0.005in became the unofficial definition. But there’s a good chance you’ll hear a design engineer say that 0.005in. is “still pretty thick."

The most sophisticated ultrathin capability today involves wire EDMing complex micro parts at thicknesses down to 0.0015in.

In Top Tool’s experience with complex precision parts, the fixture or other holding device for a micro component almost always must be custom-designed and custom-built. Unlike work holding options for larger components, there is no single fixture solution with the flexibility to do the job across a range of micro scenarios. Micro projects are inherently more complex. The more unique the micro part, the more unique the fixture and work holding solution.

"Beginning with the end in mind” leads to the proper emphasis on work holding. And how you hold a micro component certainly drives a better part. Robust part management frequently has been the difference when a previous approach did not succeed.

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