Micro-machines: worth the cost?

Micro-machine tools that are either under development or are fairly new to the marketplace are quite pricey, often costing as much as $1 million or more. I find it interesting that so-called "micro" machines have "mega" price tags. These machines have resolutions of a few nanometers, and are capable of producing high accuracy components and optical quality surfaces.

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Micro-machine tools that are either under development or are fairly new to the marketplace are quite pricey, often costing as much as $1 million or more. I find it interesting that so-called 'micro' machines have 'mega' price tags.

These machines have resolutions of a few nanometers, and are capable of producing high accuracy components and optical quality surfaces. However, especially since they are rather small systems, their daunting price tags make one think twice. Although these machines are not quite worth their weight in gold, they probably come closer to this metric than any other system that I have seen.

To offset their high cost, many micro machines have been designed to perform multiple functions, including turning (lathe), milling, grinding, planing, and inspection. The mechanical design of a number of the machines is quite ingenious. In support of multi-functional mechanical designs are a number of motion controllers that are capable of addressing the variety of functions needed for different operations.

Many functions

For example, a lathe is typically 2-axis, but the same controller is employed when the machine is configured for 5-axis machining. Of course in both cases, coordinated motor (position and velocity) control is executed. However, in grinding mode, more advanced control algorithms such as force or power control may be employed to optimize production.

Two advances are enabling the increased flexibility of these controllers. The first is more powerful processing capabilities that allow a more flexible coding of control algorithms. In the past, processing power on controllers has been pushed to the limit requiring control algorithms that are optimized for a particular configuration. New higher-powered controllers can run less efficient, but more generalized code.

The second advance is an increase in programmable memory size. In many cases, an entirely new control program is downloaded to the motion controller. Thus, a 5-axis mill controller becomes a shaper controller.

Clearly, using the multi-functional control is a necessity on a multi-functional machine. However, as the cost of these controllers decreases, they are also being employed on single use machines (such as a lathe or a mill). There are several reasons behind the conversion to these types of controllers, but most of them boil down to cost. By purchasing a single controller for a variety of machines, an OEM can cut down on programming and training costs, while enjoying cost reductions from economies of scale. Customers, on the other hand, can enjoy cost savings from a variety of avenues, including training and maintenance costs. Furthermore these controllers are quite flexible in nature, enabling some interesting opportunities.

The most widely used flexibility-enabled option is the user interface, permitting the OEM companies to tailor machines to meet specific needs or desires of customers. User interface options permit the controller to take on the look and feel of controllers with which the customers' operators are comfortable (perhaps an older model controller which may no longer be available on the market). However, this flexibility may also be used to help a company interface the machine directly to other systems such as inspection, material handling or MRP systems. The options are endless.

In the end, controls will go in the direction of increasing functionality while reducing cost and increasing profit. Newer multi-functional controllers are rapidly becoming a reality and will extend their reach in the future. As they can be programmed to behave like 'virtually' any controller, operators may not notice much of a change on the shop floor; however, designers, process engineers, maintenance and accounting will certainly notice a difference.

Thomas R. Kurfess, Ph.D., P.E., BMW Chair of Manufacturing, Clemson University International Center for Automotive Research

Related reading
This is the final article developed from my participation in a global study on micro-manufacturing. Many of the flexible controllers I saw during visits to Asia and Europe also are seen in machine tools throughout the rest of the world. Two other articles in this three part series are:

• OAC offers much to manufacturers

• Controllers advance micro-manufacturing