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Upgrading machine controls takes deep analysis, forethought, electronics know-how and comprehensive machine knowledge.

The control itself actually represents a small part of the overall retrofit cost. According to Nyles Priest, president of MachineMate Inc. (www.machinemate.com), Fond du Lac, Wis., a control itself may cost $6,000 to $9,000. However, the total cost, including installation, may be $20,000 to $25,000 for a two-axis retrofit, and higher costs for more axes and machine complexity. (That's the control only, of course, and doesn't include drives, motors and other upgrades that may be needed.)

True, some high-volume machines do have upgrade kits tailored for specific models that can bring the price down dramatically. But those kits only fit specific machine models. CNC OEMs such as Cincinnati Machine have begun developing retrofit kits for their vintage machine tools. By and large, "you need unique connections and software for a particular machine except if a special retrofit kit is pre-developed by the OEM," Priest notes. (Figure 1)

During recent years, retrofits have become most popular on machines with obsolete controls of 1980s to mid-1990s vintage. Before that, most machines that needed upgrades already have them; after, and many machines already enjoy stable, powerful controllers. Other upgrade candidates include expensive equipment, like five-axis machines and grinders. Of course, a wide range of exceptions exist depending on the application. Regardless, companies should first analyze what they have before diving into a retrofit.

A Machine's Health

First, look at the mechanical soundness of the machine, says Michael Tarr, director of global sales for MDSI (www.mdsi2.com), Ann Arbor, Mich. "Are the motors and drives stable? Do they need to be replaced, and are current replacement parts available?"

Also, he says, consider a machine's I/O structure (Figure 2). What type of sensing devices control ancillary functions? Does it have limit switches, are they active, and do they all function properly? Look for broken wires or anything out of adjustment. Having documentation, including electrical schematics and the machine's history, helps immensely.

A control upgrade can't push a spindle any faster. But controls can push servos more efficiently. "In many cases, we have the ability to tune the axes to a very high degree of positioning accuracy," Tarr says. "We have routines in the software that allow for smoothing and backlash compensation." Servo-feedbacks a decade ago had much slower scan rates. "Today, because of the newer electronics, everything operates faster," Tarr explains, "so you have a much quicker response. The quicker we can respond to a machine's motion, the more accurately we can control what it does."

Older controls might process five blocks per second. "Today, we're processing 2,000 blocks per second," explains Priest. So with a new control, "you will end up completing the part faster, not because the motors are turning faster, but because you're not losing all that time between reading blocks."

The PC and Networking

The phrase "PC-based" doesn't have the scare factor it once did. PCs today are produced in the millions with highly reliable automated testing. But, say sources, beware of standard PC-based systems that "convert" an off-the-shelf PC to a CNC through third-party software packages. "I do not consider that a real CNC," Priest says.

The industry varies on how "deep" non-proprietary hardware goes into the control, and all have various degrees of "openness." Regardless of what control is chosen, though, sources say companies should ensure machine control remains priority within the system. Both MDSI and MachineMate have non-proprietary front and back-ends in their controls—yet the off-the-shelf hardware has systems running that tailor it for machine-control operation.