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Viewpoints: About Machine Functionality and Capability

J. Patrick Ervin
It's critical that a company which manufactures machine tools understand what customers are trying to achieve from a manufacturing process and, more importantly, what they view as value-added and are willing to pay for. As a machine-tool builder, we realize that what customers demand from a manufacturing process may vary significantly, depending on what they are attempting to achieve. Some customers want basic standard machines, while others are looking for multitasking functionality aimed at completing a part in one setup. Some plan to run very large lot sizes in a completely untended process, while others will run small lot sizes with a man: machine ratio of one or two machines per operator. Some parts require very fine accuracies and surface finishes or the machining of exotic materials, while others are wide open in terms of technical requirements.

All of these factors must be assessed by a customer when deciding to purchase a new machine. What's even more interesting is the fact that the same customer can have totally different needs based on the individual manufacturing processes being established on the shop floor. Consequently, it's very common to find standard, low-cost machines and very complex, high-cost machines in the same factory. This suite of equipment demonstrates that the customer wants to match their needs to the machine purchase.

What I call customer-driven issues define how we build a machine. The machine we recommend for a manufacturing process will be based on two distinctive factors—a machine technology's capability and its functionality—factors too often conflated in the purchaser's thinking.

Capability, for our purposes, is defined as the ability to achieve a particular performance level—for example, a surface finish, a higher level of output, a closer tolerance, a higher Cpk. These factors are determined by the capability of a manufacturing process.

Functionality, on the other hand, is a machine's ability to perform certain operations within the manufacturing process. Functionality is determined by the configuration of the machine or machines employed in the manufacturing process. The functionality of a basic three-axis VMC is different than the functionality of a full five-axis machining center. A standard two-axis lathe cannot produce all the parts that can be machined on a Y-axis turning center equipped with a subspindle and live tooling. In grinding, a customer may want a standard OD grinder, or they may require a full servodriven B axis with four wheels that address both ID and OD grinding operations. The level of functionality a customer desires in a manufacturing process will determine the configuration of the machines that customer will purchase.

To help a customer select the machine that's best for their operation, we must know what's driving the customer's needs, from the parts they machine to the manufacturing strategy they wish to employ. There's certainly no doubt that customers today are asking for varying degrees of both capability and functionality, often in the same factory.

Adding functionality to a machine is pretty self-explanatory. We add functionality by increasing the machine's ability to multitask and automate a process. Adding capability is, however, far more daunting, and is hidden beneath the surface. Doing so really involves the core of a machine's structural design: the size and weight of the base casting; the width of the way system; the diameter and rating of the ballscrews; the power and speed of the control and drive system; the ability to control thermal stability and machine damping. All these factors play a major role in determining what a machine can actually achieve in terms of accuracy and output.

Achieving higher performance requires designing and building machines with higherperformance structures and components. No reasonable person expects his or her minivan to perform like a racecar, and the same sort of evaluation applies to machine tools. Many times product features are overlooked, now that all machines are shrouded in crisp, clean, sheetmetal enclosures. Often, customers estimate the performance level of a machine simply by measuring its functionality, because functionality is visible. Capability is not.

What all this means is simply that the price of a machine tool isn't an arbitrary number; it's driven by customer needs, which in turn are driven by the parts made by the customer, and the manufacturing processes that are necessary to make those parts to specification. The customer who bases a purchasing decision only on price may find that his machining solution provides neither the functionality nor the capability required to enable success on the shop floor.


This article was first published in the July 2008 edition of Manufacturing Engineering magazine. 

Published Date : 7/1/2008

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