CHOOSING THE RIGHT TOOL FOR MICROMACHINING: HERE'S TO KEEPING YOU ON THE CUTTING EDGE

The continuing pursuit of manageable-sized manufactured goods has led to increasingly smaller cell phones, laptops, even portable gaming consoles, and continues to pave the way for new medical technologies and space exploration. While a new design may look great on paper, if you can't find a way to make it, then it remains just an idea. Manufacturers continue to clamor for more—smaller scale, faster speed, better finish, higher accuracy, a broader spectrum of workpiece materials, and of course, reduced costs. To meet these demands, the right tools are a key part of the production equation.

Like most challenges, micromachining does have a solution, once you know how to read the terrain correctly. The different natures of the workpiece materials such as copper, aluminum, various steel grades, as well as exotic materials like titanium and graphite, suggest the need for material-specific tool geometries and coatings. The tiny scale of micromachining, along with the twin demands of production efficiency and a high return on tooling investment implies that solid carbide rather than steel is the choice for tooling construction. These three components: geometry, coating and substrate, define the correct cutting tool for a given application. That combination varies from one material to another.

GETTING IT RIGHT

If parts do not meet tolerance in terms of dimensional and finish requirements, they are not parts, they are doorstops. Tool flex leads to vibration, runout and poor finish quality. Over time, this means additional stress and maintenance will be placed on machines. More immediately, it means increased energy to make each part, since some of the energy is translated into unproductive tool movement instead of cutting force. These unproductive forces also shorten tool life, leading to increased frequency of tool replacement and additional tooling purchases. You can minimize these issues in your tool selection by using solid carbide tooling with geometries tailored to the specific applications and materials.

EFFICIENCY AND RETURN ON INVESTMENT

Broken tooling means tool changes, machine setups and a higher risk of missing deadlines and scrapping parts. The most appropriate tools for micromachining are made from ultrafine grain carbide, which eliminates the need to machine workpieces prior to hardening. These tools also use the thinnest and most durable tool coatings possible. This means a sharper, longer-lasting edge can be honed, resulting in more machine uptime and more production per unit of energy.

Conversely, while longer tool life means less time changing tools and setting up machines, it also means more time making a product. This results in a greater return on tooling investment. Tooling designed especially for micromachining is a solution that's responsible to the bottom line.

NEW TOOLS FOR MORE CHOICE IN MATERIALS

Tool geometries specific to the material being worked yield higher removal rates and better chip evacuation, reducing the risk of tools bending and breaking, thus yielding faster production times. As an example, chip control is more challenging when working with soft, malleable materials; these chips tend to stick to the cutting edge. Flute geometry changes the chip path gradually, which inhibits adherence. In these applications, tool coatings are primarily for lubrication versus a thermal barrier; however, heat is the major issue when working harder materials. Titanium Aluminum Oxide (TiAIN) is an excellent choice. TiAIN is more heat-resistant than Titanium Nitride and forms a layer of very hard, low friction aluminum oxide at working temperatures, which aids in chip evacuation and minimizes heat transfer from the chips back to the cutting tool.

One company offering this range of solutions is Seco. A recent expansion of its Mini line of endmills includes coatings, carbide grades and cutting geometries well-suited to harder metals like steel and titanium, softer metals like aluminum or copper, and highly abrasive materials such as graphite. These new tools are available in diameters down to 0.1mm.

ENVIRONMENTAL FACTORS

Choosing the right tooling isn't the only way to make accurate micromachining more cost-effective. Keeping your shop's ambient temperature within a narrow range and minimizing the difference between the warmest and coolest spots in production areas will reduce thermal expansion. You may want to experiment with leaving a combination of ceiling lights on at all times. The very small tooling used for micromachining will absorb heat from inspection lights quickly, so turn them off when not in use.

Be aware that machines have work zones. You can more accurately maintain the entire work area of the machine by setting your jobs up at different zones on the worktable. When a machine is not in use, remove any unnecessary heavy items from the area. Keep your workpieces clean. Neatness is not just a safety issue—a stray chip can be the difference between shipping a part and making an expensive paperweight.

MEASURE TWICE, CUT ONCE

Double- and triple-checking a measurement takes less time and costs less money than starting over entirely. Ruining a complex part is much more expensive after several processes have been run than at the beginning.

Proper care of your production machines is also a must. Make sure you maintain a regular calibration schedule, keeping accurate and detailed records of each deviation or adjustment.

Production personnel meetings can be forums for sharing ideas and techniques that improve your processes— learn as much as you can from your own experience. Your whole team, and ultimately you, will benefit. Stay current on the latest tools, machines and methods. The demands of your micromachining clientele will continue to change and you must adapt with them.

THE RIGHT COMBINATION

The right combination of carbide coating and geometry provide a significant reduction in production cost and improve a manufacturer's abilities to meet deadlines while holding tolerance and finish requirements.

Finally, remember that small variation in cutting tools can significantly impact the High Speed Machining process. To ensure each tool performs the way you expect, stay with one supplier for each type of tool used.