Rebuilding and reconditioning is an important line of business for Caterpillar – the world’s largest supplier of construction, earth-moving, and agricultural equipment. For the equipment owners and operators, rebuilding makes economic sense, particularly with regard to the hydraulic components. Since 2008, rebuilding has been in such demand at a Corbin, Ky., Caterpillar dealer that it has added machining capabilities to its hydraulics shop.
Among the critical components now installed at Whayne Supply is a Sunnen HTA tube hone: it allows Whayne to resurface scratched and rusted cylinder barrels, reportedly saving customers 80% or more over the cost of a new barrel. Brought in during 2009, as part of a beta test of Sunnen's new all-electric machine design, the hone has been used to process more than 1,000 barrels in the three years since then. Bringing this previously outsourced machining work in-house has helped Whayne to increase its revenues and add new staff, and to improve delivery schedules and costs for customers.
Whayne is Cat-certified to conduct complete machine rebuilds: Since 1985, it has completed more than 400 rebuilds on 33 different machine models. In 2001, it was honored for completing the 5,000th Cat-certified rebuild. Whayne has 14 locations and approximately 1300 employees. Of those, 200 are at work in the Corbin shop.
"Simple economics dictate that customers are going to be rebuilding machines until the economy – and the coal industry in our region – both strengthen significantly," said Mike Harbin, Manager of Whayne's Power Rebuild Center. "We have customers who are tearing down machines in the field and completely rebuilding them. The machine shop and the honing system have helped us stay on top of this trend. We have added five people in our shop alone to handle the increased volume."
Whayne has rebuild centers in Louisville and Corbin, where all of its Caterpillar exchange/re-sell goods are processed. The Corbin hydraulics shop has eight cylinder technicians, three full-time machinists, three pump experts, plus a foreman and service coordinator. In 2009, this operation added machining to its hydraulics shop, including two vertical mills, two lathes, drill press, rotary surface grinder, welders, and saws. The shop stocks various sizes of chrome-plated bar and DOM tubing, some of it pre-cut for standard Cat sizes.
Customers save, shop profits
This new shop has five cylinder service bays, one for suspension cylinders, one for lift cylinders on small loaders, and three for high-force cylinders. "We can replace the barrel, rod, rod eyes, head/seal areas, hydraulic lines and connections, or custom-fabricate new cylinders to spec," explained service coordinator Michael Carter. There are four hydraulic cylinders on the average Cat machine, so the shop stays busy, processing about 1,000 cylinders in 2011.
"During the summer, we may have a hundred or more cylinders outside our shop waiting to be rebuilt, because our indoor storage is full," Carter added.
The Corbin shop's previous hone consisted of a drill motor on a sliding carriage, and lacked the power, capacity and rigidity needed for doing serious work, according to Carter. "It could produce a surface finish, but not remove metal."
Whayne agreed to beta test Sunnen's all-electric HTA cylinder hone, and later purchased the machine with a 12-foot (4 m) part capacity.
The HTA tube honing system handles parts weighing up to 8,000 lb. (3,629 kg), with ID ranges from 2.5 to 21 in. (63.5 to 533 mm.) It is designed to resurface and repair machinery and parts requiring light-duty stock removal up to 0.030 inches (0.76 mm.) Standard models are sized for 6-ft (2 m) and 12-ft (4 m) part lengths, and custom lengths are available, too.
Setting machine parameters
The HTA is equipped with a Siemens drive and PLC-control with touch-screen HMI for setting machine parameters such as stroke reversal point, spindle/stroking speed and crosshatch angle calculation. The control features a load meter to determine areas of bore tightness, and provides the ability to dwell the tool in multiple areas to correct part geometry.
A touch screen-controlled hone provides a safer working environment and reduces operator fatigue. It also provides better quality parts by producing a controlled crosshatch pattern, which allows the honed surface to retain oil or grease, ensuring proper lubrication and ring seal of pistons in cylinders.
"We were not sure about downtime for a new machine,” Carter continued, “but it has proven extremely reliable and we've used it to hone cylinders from 2.5 to 17 inches (63.5 to 432 mm) diameter, and six inches (152 mm) length to over 21 feet (6.4 m)," Carter added.
"We simply created a table with an adjustable-height V-block to support parts that overhang the machine. We have used up to a 21-foot drive-shaft length on the machine, and we can hone from both ends of the part if need be. Our cycle time for most barrels is about 30 minutes, which includes setup, honing and washing the part," he said.
Whayne uses both roughing and finishing abrasives, removing scratches and rust, and imparting a specific crosshatch surface finish on the barrel bore. "We can increase the cylinder bore diameter up to 0.254 mm (0.010 in.) in aa relatively short time, removing rust and all but the worst scratches, and remain within Cat machine specifications," Carter said. "Our old hone simply could not do this. The HTA hone is easy to setup also. The control calculates the correct crosshatch angle. It's been a very reliable system, too, with no appreciable downtime.
"We scrapped a lot of hydraulic barrels or sent them out to other shops prior to acquiring this machine," Carter added. "Now we can salvage a cylinder with honing, and the cost and time for the customer is a fraction of replacement. In the current economy, customers appreciate this."
