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Breathing new life into an old workhorse: "machine rebuilds are a cost effective alternative for many shops looking to increase capabilities and performance". (Holemaking/Boring/Tapping).

So says Richard Bikle, president, Bikle Manufacturing, Inc. (Smithsburg, MD). He should know, having recently completed a rebuild of a large 1952 Giddings & Lewis boring mill for use in his own job shop, which specializes in precision machining and tool rebuilding.

"To replace an old boring mill of this size, you're talking about spending close to a million dollars for a new one," says Bikle. "For us to rebuild it and install a modern NC control on it, the cost was about 20% of that. Currently, the machine is in use about 50% of our work day performing milling and boring operations on very large parts."

Bikle explains that the rebuild took only a few months to complete, including having the entire machine refitted and rescraped. The old screws and motors were discarded, and new ballscrews were installed with digital AC servo motors. The spindle gearing was thrown away, and a timing belt drive and servo motor were installed on the spindle providing accurate control from 1 rpm - 2500 rpm.

"To bring this machine into the new century, we installed a Heidenhain TNC 426M contouring control with integrated digital drive technology, and Heidenhain AC servo motors," explains John Palmer, one of Bikle's electrical engineers. "We had to choose something that would best suit our needs, as well as that of our customers'," explains Palmer, citing that Bikle Manufacturing also offers machine rebuilds and retrofits to its customers.

The Boring Mill Today

This particular boring mill is especially useful for the really large parts that Bikle handles. Its X-axis travel is 10, the W-axis is 14', and the Y-axis is 9'. The quill travel is about 6'. The machine can accommodate parts averaging about 9' in diameter and up to a 70,000 lb. in weight.

When this machine was built in the 1950s, it was of course, manually operated and had a maximum spindle speed of 400 rpm. With the rebuild, it was converted into a modern NC machine with a spindle speed of up to 2500 rpm.

"I'd say the most challenging part of this rebuild was actually fitting the ballscrews into the castings," said Palmer. "The castings were not designed for ballscrews and we had to do some re-machining.

"One of the easiest parts was incorporating the Heidenhain control," continues Palmer. "It was actually the easiest one I've ever done because we started from scratch. We didn't have to interface with anything else. It was building the system from the ground up."

Bikle added that the iron on many old machine tools is often superior to what you get on a new machine today, so that updating an old machine and turning it to an NC incorporates the best of both worlds.

The Control

The new Heidenhain TNC 426M control on this boring mill breathes new life into this old machine. "Out of all the controls we have in this shop, this one is clearly the best," says Bikle when speaking about speed and accuracy.

The machine's maximum travel speed is now at 350 ipm, and is accurate to 0.0002". "The speed and accuracy are really impressive when you are talking about moving this much mass," notes Bikle.

"From an electrical engineer's standpoint," adds Palmer, "the ease of use of this control is great. I can machine parts myself on this old boring mill because it is so easy to use."

"Our machinists like this control too," explains Palmer. "The learning curve on this control is very short because of the way that the machine and the control are set up. It basically asks everything it needs to know to make the part you want. It's very conversational."

Palmer adds, "Also when compared with many other controls, for example, Heidenhain's cycles are better developed. Many others are not user-friendly. Now to someone that has CAM software and a programming department to program parts and send them out to the control, it wouldn't make much difference. But here, where we're a job shop, we're not making the same part 300 times a day so every job is different. The ease of use of the control right on the shop floor really is key to our situation."

Being shop-floor programmable is important to a job shop. Even when production drawings are not dimensioned for conventional NC programming, the Heidenhain TNC provides FK Free Contour Programming to do the necessary calculations.

Heidenhain's TNC 426M controls machines with up to five axes plus a controlled spindle. The powerful microprocessor hardware ensures fast block processing times even for long part programs.

Rebuild Considerations

Bikle adds, "Currently there are a lot of people with big old boring mills or vertical turret lathes in place. And, really, the only improvement in machine tools since the '30s has been the gauging and controls and a few accessories, so I always recommend considering a retrofit or rebuild before buying new.

"Especially when evaluating large machines, the cost is often a fraction of what it would be to buy a replacement. You see, it's not only the cost of the machine itself but also the cost of removing the old machine and reconstructing the site to accept the footprint of the new machine. That in itself can cost as much as an entire rebuild."

Bikle Manufacturing is lucky to be able to do their own rebuild work, but does offer that service to others. "We have the people to handle machine rebuilds here and the supplier connections to get the components we need," said Bikle. And, obviously, they do practice what they preach.

In a tight economic climate, breathing new life into existing equipment proves profitable. Bikle Manufacturing is one example of this. Heidenhain Corp. or Circle 204 for more information
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Publication:Modern Applications News
Geographic Code:1USA
Date:Feb 1, 2003
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