GETting the Right Balance

Ground-engaging tools, or GETs, are a challenge of balance in material and design. Materials must be wear-resistant with hardness, yet tough enough to take impact.

"Ground-engaging tools are not just a piece of steel that sits out there and is priced at X number of dollars to be competitive in the marketplace," says Kirk Yoresen, marketing communications manager for Esco. "It doesn't do any good to save 20 percent on the purchase of a ground-engaging tool if it winds up costing more to operate because of shorter wear life."

Each component of a digging system in mining or construction serves a different purpose, and the composition of each piece is balanced to create a working tool, Yoresen says. The bucket lip is a structural component. It needs to have wear capabilities, but it is primarily structural. Then the adapter or shank that attaches the teeth to the bucket, "is kind of a structural component, but it has to take a tremendous amount of toughness and wear life to go along with just attaching to the bucket," he says. The shank would be made of a different material. Then there are the teeth, which are made of an even harder material. "But they also must have toughness to withstand impact.

"Each of the materials of these components is different, depending on whether or not an item is welded on or mechanically attached in some way."

To prolong the wear components' lifecycle, Esco and other manufacturers have begun to move toward carbide-impregnated wear surfaces "laid on by various processes that involve subsequent heat treating," says Yoresen. "They are more expensive, but they do reduce your down time. Rather than changing teeth once every month, you're increasing that two or three times."

Balance in materials must also be seen in relation to machine performance, says Bob Klobnak, senior product consultant for Caterpillar Ground Engaging Tools Division. "In order to get longer-wearing components, you have two primary choices: Make it harder or make it bigger," he says. "Most material development to date has come about as far as it can in material hardness properties in the base piece itself. Of course, bigger frequently can be negative to the productivity of the machine.

"At Caterpillar, we spend a good deal of our effort in trying to balance the wear-protection element of the GET with the effect it has on machine performance. Making something bigger to last longer is sometimes not a good idea, depending on how it affects the productive capability of the machine."

Jason Simmons, a ground-engagement tools engineer for John Deere; and Dana Klostermann, product manager at Deere's marketing service group, say that the way components are manufactured has changed.

"A lot of manufacturers are now using parts from castings that previously were forged," Simmons says. "The movement toward castings is because forgings are more expensive, so there is an economic motivation, and improvement in casting quality has closed the gap on performance." This shift, he says, has occurred over the past three to five years.

Kenco has seen the results of these material changes, says operations manager Tracy Black. "We don't actually manufacture any teeth ourselves, but we do see quite a variety of teeth and shanks out there for our customers," he says. "Tooth manufacturers are constantly looking at bettering their products and offering more specialized teeth for certain applications, whether you're digging in rock, clay, sand or whatever. There are more and more options every year, and as manufacturers make teeth to last longer, customers are more productive and make more money."

Many design changes in GETs have been brought about by end-users. "People call in with really good ideas for specific needs, and this turns into engineering that designs something for that customer's specific needs," Black says. "Eventually that idea becomes a product that's available to everybody."

Preference for one system over another varies as much as the customers themselves, says Deere's Simmons.

"Customers may have other buckets in their fleet that have a particular style system," he says. "For commonality purposes, they would select one system over another. Customers look at different cost associated with different systems, and each of those systems range in different sizes. Bigger machines require a bigger system. They need to know the breakout forces of their machines and make sure they have the right system size to match the size of their machine."

Deere identifies six basic retention systems to enable an end-user to determine what manufacturer or adapter or tooth they are using.

• Pin and washer. On a Caterpillar-style replacement system, according to Deere, a pin and washer, or split washer, goes into the adapter before the tooth is slipped into place. You insert the washer, slide the tooth on and pound a pin through that. It also has a groove that lines up with the washer that retains the tooth.
• Flex pin system. These are common on replacement teeth used on John Deere backhoes, for instance. The flex pins are two steel forgings that have a neoprene rubber in between. "It looks like a sandwich," Simmons says. "As you pound the pin through, it squeezes the neoprene and that holds the tooth up on the adapter."
• Roll pins. This looks like a steel coil. The pin is pounded down through the top rather than through the side. Roll pins are traditionally used on Hensley style systems, according to Deere.
• Steel key. This style is used on bigger Hensley systems. Once inserted, the key has to break a tab to remove it.
• Esco's Quadrilok horseshoe-shaped pin. The tooth does a quarter-turn twist to get on the adapter, according to Deere. The horseshoe prevents the tooth from twisting back off.
• The Esco-style Super V system. This is similar to flex pin, but instead of being pounded in horizontally, it is pounded in vertically at the very back corner of the tooth.

Yoresen says Esco has "always prided ourselves on quick change. But in addition, we and the industry are moving toward improved safety. And that means we are moving toward hammerless design. A wear component can be changed without the use of a sledge hammer or pin or any other type of tool.

"Hammerless design is not easy," he says. "You want something that is easier to remove, but you want it easy to remove only when you want to remove it. You want it to stay in place, and that is the design challenge today."

Caterpillar's Klobnak concurs. "Our K Series is hammerless in the larger sizes where it makes more sense," he says. "Vertical orientation of retention generally makes it easier to remove and install, especially on close space adapters, such as those on an excavator. On a large loader, where the adapters are spaced further apart, whether it's vertical or horizontal accessibility is less of an issue, although removing the vertical retainer is usually still easier."

Application determines what profile tooth to use, according to Simmons, and he identifies four general profiles that seem to cut across all the different systems.

The standard profile tooth has a general profile used for usual digging applications, such as dirt. It is not a high-impact tool, but is just a good digging tool that wears adequately, Simmons says.

The flare-style tooth, instead of being straight at the end, flares out to create a second lip on the bucket and add capacity, Simmons says. "This is good in loose material like sand or dirt. It adds extra capacity and the material is already broken up, so you don't need it for penetration."

The tiger profile has pointed teeth. These would be used on center adapters of a bucket. Twin tigers, which have two points, would be used on the ends of the bucket, says Simmons. "These teeth are used in frost or hard compacted ground where you need penetration. They are used either to penetrate hard material or to break through it. Some customers use tiger and twin tiger teeth for breaking rock," he says.

Abrasion teeth are for customers working in sandy or rocky conditions who need extra wear material on the front point end of the tooth.

Caterpillar's K Series features entirely new shapes, Klobnak says. "New shapes come with new names or new series. For us, our K Series features all new shapes. The teeth last longer and penetrate better. Usually, you can equate sharpness of the tooth with its ability to penetrate."

A longer tooth can provide more wear material and more penetration, he says, but there is the balancing factor again — you have to balance length against strength. "The longer you make a tooth," he says, "you can affect the strength. And you affect the breakout or performance of the machine itself. All of that has to be balanced."

The industry seems to be emphasizing the performance of GETs, Klobnak says. "The trend today is not only to protect, but to have a productive system and maintain the productivity of your work tool as your GET wears."