Machine builders, manufacturers of cutting tools, and end users are finding that the use of conventional bearings often results in long-term problems such as increased maintenance, downtime and scrap costs. The use of quick-change rotary bushings eliminates those problems while solving the need for improved accuracy and quality.
With all the global competitive pressures, you would think that manufacturers are so focused on productivity and quality that no process or technology advantages would escape their attention. This would seem especially true of proven machining technologies, where such advancements are likely to result in longer service life and the avoidance of consequential machine tool damage, excessive scrap and exorbitant downtime costs.
Yet, as with most capital investments, end users are usually concerned with initial purchase price, and machine builders feel they must compete on price. While those pressures are understandable, they are nevertheless old school, and can be a major barrier to productivity and profits.
“In today’s cutthroat markets, it may be tempting for any supplier to cut corners – to not be as responsive or quality-conscious,” says John Ciniro, president of Master Tool Corp., Grand River, Ohio, “because customers are continually trying to get their suppliers to cut costs. But we really can’t afford to cut corners with our design, and build tooling systems. That would hurt our customers and us. We are known for making sure that we give every customer products that are accurate and dependable.”
Rotary bushings: Long-term accuracy
The need for accuracy and dependability certainly applies to bearing assemblies. While often considered secondary detail parts, they are certainly not secondary to performance. Bearing failures lead to all of the problems mentioned above – and can shut down a production line for excruciatingly long periods.
For those reasons, rotary bushings - self-contained bearing cartridges - are becoming indispensable in precision metalworking applications ranging from gun drilling to cutting tools and inspection fixtures. In most of these applications, short-term thinking is becoming a thing of the past, due to the vastly improved performance of rotary bushings, or the unfortunate loss of the ability to compete.
The tough automotive market, where precision line boring and cutting with continuous uptime is crucial, provides many good examples of how advanced, anti-friction rotary bushings are becoming the standard for tool builders and end users alike.
Rotary bushings are self-contained bearing cartridges used to support and guide rotating cutting tools. Used instead of detail parts (e.g. individual bearings), these packages are more expensive, but offer many advantages that have become crucial to long-term accuracy and uptime.
Master Tool, which designs and builds special tooling for machining automotive transmissions, engine blocks and cylinder heads, incorporates rotary bushings designed and manufactured by Gatco, Inc., Plymouth, Mich., into its cutting packages.
“Master Tool and Gatco work together to create an optimum solution,” Ciniro explains. “This applies especially to material that is not easily machined or has a weakness characteristic that may cause the cutting tool to chatter or vibrate. Over the years, both companies have developed the technologies and know-how to overcome those problems, which is essential to safeguarding that we don’t have to redo the tool again . . . that it will produce quality and reduce downtime.”
Rotary bushings: Precise support
Bill Jodway, OEM sales manager at Valenite, LLC, Madison Heights, Mich., says his firm uses Gatco rotary bushings for crankshaft boring bars that are 40-in. to 50-in. long. “We use the bearing bushing to support precisely, so that when we bore the crank, it can be held within 0.0002-in. journal-to-journal. That tolerance is critical to keeping the motors going,” he says.
Jodway says Gatco is able to hold very close tolerances on bearings and seals, and provides very tight rotary bushing construction. “That is important to long-term performance,” he says. “With all of that iron dust that occurs during the machining of engine blocks, it’s important that the dust doesn’t get inside the rotary bushings and score the bearings. That stabilizes our cutters. So, it’s a nice marriage between the machine tool and the bearings, and the rotary bushings are basically what holds it all together.”
Jodway adds that the rotary bushings are a bit more expensive, but that the added performance more than justifies cost. “The way we approach customers with cost-performance factors - we call it "dollarizing" – is that with assured accuracy and less downtime, the more production they can do at the end of the day. That’s an important part of how we sell our product, and the Gatco rotary bushing is an integral part of our product in gang arbors and other specialized machine tools.”
Until now, the design of a great many cutting machines incorporated the use of individual parts that comprise the bearing support and were built into the machine housing. The inherent limitation of this design is that when new guide bushings are installed it may be necessary to remove the entire housing, rebuild it in the tool room, and then realign it back on the machine – further delaying production. This can also occur when the bearings, seals, or components go bad, and repair or replacement is required. Downtime results in both cases, and it always turns out to be extremely expensive.
A rotary bushing retrofit to a more easily replaceable part, on the other hand, can help stave off downtime. To accomplish this task, Gatco developed a quick-change, precision cartridge with a self-contained bearing assembly that is machine-installable in mere minutes, and eliminates the time consuming and expensive replacement of individual detail parts.
A global manufacturer of high-speed diesel engines realized this advantage in its camshaft and crankshaft line boring operation, where the end and center supports contained tapered roller bearings. Whenever the bearings needed required changing, which was quite often, it took valuable production time to get them all set-up.
“We had to get the bearings out, get the spacers all set,” explains a maintenance engineer. “We had a lot of trouble with those things.”
To solve the problem the plant adopted a program whereby older bearings would be replaced with Gatco rotary bushings. “They are a modular setup, so all you have to do is slide one out and slide another one in, bolt the machine back up, and you were ready to go,” the engineer explains. “We went from changing bearings out at least every six months, to changing them only every couple of years.”
The result was a large savings in machine troubleshooting and maintenance, significantly improved uptime and throughput, and reduced scrap due to more consistent quality. “The change to the rotary bushings touched all the bases,” the engineer says.
A cost-effective solution
John Palazzolo, sales manager of Gatco, says that in spite of the advantages of the rotary bushing technology, some end users inadvertently have machines built that still include troublesome detail bearings parts instead of quick-change cartridges.
“The machine builder may insist on building their own bearing supports, and they do it with detailed parts, not cartridges,” Palazzolo explains. “It may be cheaper for them, but in the long run its very expensive for the end user of this machine. Further, when it comes time to repair the support consisting of indi