Bushing retrofit cartridge is way to defeat downtime

Tooling & Production, Sep 2006

Rotary bushings are commonly deployed in transfer line tooling applications such as automotive engine block cam and crank boring. They pay automakers significant efficiency dividends because they guide line boring bars with the frictionless support they need to machine precision bores. A stride beyond the more common-and better known-common drill bushing, rotary bushings not only facilitate accurate cutting but also do away with heat, wear, and chatter. Their use in production can boost CPK value as well, a calculation that gages the extent to which a process has met the quality specification limits established by customers.

Although rotary bushings are a small but vital component of high-volume manufacturing, they can also be an Achilles' heel. This is attributable to the design limitations of most boring machines. Past practice involved mounting individual detail parts directly into the machine housing. The line boring bar moves through the bushings' inner diameter and-with the help of precision bearings-rotates without friction. The design of a great many machines involves the use of individual parts that comprise the bearing support and are 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.

These rotary bushings, frequently referred to as "Gatcos," make a machine housing rebuild and realignment completely unnecessary. Rather than removing worn parts, ordering new ones, and installing them, one simply slips the new cartridge in place and locks it down. Moreover, all the quick-change cartridges are factory pre-adjusted to customer specifications.

Gatco pioneered the anti-friction rotary bushing, and currently supplies the metalworking industry with a virtually limitless range of shapes and sizes. Gatco rotary bushing solutions are customizable to requested design specifications and arc deployed in manufacturing plants worldwide.

Downtime happens

As time is literally money in auto manufacturing, stalled production taxes a manufacturer. Given fierce international competition, spiraling labor expenditures, and microscopic profit margins-even a little downtime is extremely costly and should be avoided at all costs.

Even so, some amount of downtime will occur anyway, particularly where line boring bar supports are concerned. In a typical parts-punishing, high-production application such as engine block boring, trips to the tool room for repair and replacement are unavoidable and may be required several times per month. This can be a detriment for a U.S. automaker competing with top Asian competitors.

Companies such as Toyota, Honda, and Hyundai have mastered their production processes through incremental tweaking, and learned how to transition product from the manufacturing floor to the sales floor virtually without interruption. Taking a cue from the Asian example, American automakers and the industries that serve them are working on concepts that enhance production efficiency one step at a time.

A rotary bushing retrofit may prove a small but important step in that direction.

Successful retrofits

Galaxy Industries is a machine shop based in Canton, MI, that performs a range of machining work for major equipment manufacturers such as Caterpillar Inc. and Eaton Corp. Galaxy used three bushings in engine block boring to pilot the line boring bar, and in 2005 all three wore out near the end of a Caterpillar job. Though the company had a spare set of bushings on hand, the cure wound up being worse than the disease.

"When the bushings wore out we were at the point in the job where we were ready to bore all seven crank journals in the engine block simultaneously," plant manager Dale Funk recalls. "We had another set of bushings available but we didn't realize they were the wrong size until we had completely torn down the existing setup to install them. There had been a change in the crank bar, and it turned out that the bushings we had were too small. It really messed us up."

Armageddon followed. The operation ground to a halt for 24 hours, and the delay cost the company $150,000, not a penny of it recoverable down the road. That, by the way, did not take into account the $25,000 Galaxy had already invested in off-size bushings, or the time and labor entailed in the fruitless disassembly operation. Fortunately for the company, there would be a happy outcome.