PC-Based Control Retrofit
Boosts Uptime To Near 100%

This 10-year-old three-axis machining center still had good iron and was capable of making high-quality parts; but control problems made it usable only 20% of the time.

In 1995, Melling Tool was looking to replace an expensive three-axis vertical machining center (VMC) that had an unreliable, out-of-date control. The company was having trouble finding a buyer for the older machine, even at $13,000. Now, thanks to a new control, not only has the machine’s performance improved, but Melling also discovered a money-saving way to expand its manufacturing capacity.

Open CNC retrofits older machine toolsThe control that rescued the VMC is OpenCNC®, a production-proven, software-based CNC (computer numerical control) for machine tools from Manufacturing Data Systems, Inc.™ (MDSI™ - Ann Arbor, MI). OpenCNC requires no proprietary hardware or motion control cards. Control replacement with OpenCNC not only promises to save money by extending the productive life of machine tools, but at Melling, it also improved the VMC’s performance over the original control. Most significantly, Open CNC enabled the company to expand into new markets without a large, additional expense.

Melling’s dilemma with its machining center involved three problems. The machine tool’s obsolete proprietary control required operators to master a hard-to-use programming language, and the learning curve was proving to be too steep. There also were limitations as to what parts could be programmed on the machine. Finally, after a few years, downtime had increased until the machine was only usable about 20% of the time. “Nobody wanted to use it,” recalls Tom Foster, Melling’s CNC mill department supervisor. “It was our weak link.”

Melling found itself at the same dead end that manufacturers have confronted for years: how to salvage a usable machine tool with an obsolete control without spending more than the hardware was worth. The company considered changing the control on the machine to another, conventional “black-box” proprietary control, Foster notes. “The new vendor quoted $35,000, plus another $5,000 for time and materials. When you’re talking about a machine you’ve been trying to get rid of for $13,000, it doesn’t make sense to put $40,000 into it. It was beginning to look as if scrapping the VMC was the best idea.”

OpenCNC came to Melling’s attention through reports of its application at a nearby plant, Great Lakes Industries (Jackson, MI). At Great Lakes, 15 machine tools were retrofitted with OpenCNC, including lathes, machining centers, and gear hoblers. Due to the changeover, Great Lakes had doubled its capacity and reduced downtime to near zero — all at a fraction of the cost of conventional proprietary control solutions.

“We were skeptical that anything could be as good as OpenCNC seemed to be,” reports Dave Horthrop, president of Melling Manufacturing Group, a group of subsidiaries that produces various parts, fittings, and assemblies for the aerospace, automotive, medical, and prototype/tooling industries. “Instead, it has turned out to be much better than we even hoped.”

Upgrading Older Machines, Virtually Painlessly

The changeover to OpenCNC was trouble-free all the way around. The shop removed the old control, installed an office-grade PC (personal computer) loaded with OpenCNC software, and started running parts shortly thereafter. Operators quickly noticed the advantages of software-based control. “You can spot a machine with OpenCNC just by looking at the back of the machine tool,” says Horthrop. “We were able to get rid of most of the electrical cabinet. Now there’s nothing there except a few wires. It’s very simple.”

They also were impressed that they could still use the drives and motors that were already on the old VMC. “The retrofit was relatively painless,” agrees Tom Foster, CNC mill department supervisor, who did the retrofit himself in less than two weeks. “Even though the integration was new for me, it went pretty fast. And, because with OpenCNC we were able to use the same programming language we use on all our other machines, it was very easy for the other operators and set-up people to run it. It felt like coming home.”

The results after retrofit are impressive. The formerly nonproductive machine started running at full capacity, and it has continued to perform since the changeover without any problems. Uptime has increased from 20% to 100%; and, the machine’s productivity improved by 50% using the existing drives and motors more efficiently. “Before OpenCNC,” according to Foster, “the maximum rapid rate on the (earlier) control was 390 ipm (inches per minute). After OpenCNC, it’s 590 ipm. Over a 5,000-piece run, that makes a huge difference.”

Horthrop feels that OpenCNC is as user-friendly a control as they have ever seen. “Thanks to OpenCNC, any operator can be assigned to that piece of equipment. The dependability and uptime have been virtually 100%. It operates multiple shifts every day, five days a week, without any problems whatsoever.”

OpenCNC has proved to be completely compatible with Melling’s NC programming systems, SmartCAM® and MasterCAM®, giving the VMC’s operators DNC (direct numerical control) capabilities for the first time. OpenCNC’s software includes a fully integrated DNC capability that enables the machine tool operator to download part programs when they need them.

Unlike conventional controls that depend on proprietary hardware or motion control cards, OpenCNC continues to operate economically throughout its life cycle. “If you need a replacement board for a proprietary control,” says Foster, “it’s only available through that company, and generally they’re very expensive. With OpenCNC, replacement parts can be bought at more than one place. We can buy a PC at any local discount store.”

The cost-effectiveness of the OpenCNC control has enabled Melling to add manufacturing capacity at a fraction of the cost of buying new CNC machine tools. This has freed the company to consider new markets that otherwise would have been very price-competitive. “We used to disregard certain used equipment on the market based on the control,” says Horthrop. “Now, I’m looking at old stuff with an entirely different attitude. We’re currently looking at equipment for retrofitting to use in a mature market we haven’t been in before. Before OpenCNC, it wasn’t cost-effective. But, when you can retrofit a high-quality old machine tool for a nickel on the dollar, it opens up all kinds of new possibilities.”

Horthrop believes that Open CNC will change the manufacturing industry, as he knows it, in several key ways. “OpenCNC will extend the life of machine tools,” he explains, “and it will allow companies like Melling to compete in new markets at a competitive cost.” Most of all, Horthrop is hoping to see OpenCNC on new machine tools. “If OpenCNC were to become widely available on new machine tools,” he says, “it would be of tremendous interest to us. To have a control that you can maintain yourself and upgrade as easily as you do with any other software — this will be the way, I believe, that everyone will want to go.” MDSI – Manufacturing Data Systems, Inc.

- August 2000