Rebuilding heavy equipment makes good economic sense particularly for the hydraulic components on construction and earth moving machinery which supported the addition of a machine shop as part of the existing hydraulics shop at Caterpillar dealer Whayne Supply in Corbin Kentucky.
The shop’s key equipment includes a Sunnen HTA tube hone which allows Whayne to resurface scratched and rusted cylinder barrels. The company said this could save customers 80 percent or more over the cost of a new barrel. Brought in as part of a beta test of Sunnen’s new all-electric machine design in 2009 the hone has been used to process more than 1000 barrels.
“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.”
“We can replace the barrel rod rod eyes head/seal areas hydraulic lines and connections or custom fabricate new cylinders to spec” said Michael Carter service coordinator. There are four hydraulic cylinders on the average Cat machine; the shop processed about 1000 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 shop’s old 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” he said.
Whayne tested Sunnen’s new all-electric HTA cylinder hone and later purchased the machine with a 12-foot (four meter) part capacity.
The HTA tube honing system handles parts weighing up to 8000 pounds (3629 kg) with ID ranges from 2.5 inches to 21 inches (63.5 to 533 mm). It is designed for resurfacing and repair work where light-duty stock removal up to 0.030 inches (0.76 mm) is required. Standard models are sized for six-foot (two meter) and 12-foot (four meter) part lengths and custom lengths are available.
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 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 said. “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.”
Bringing this previously outsourced machining work in-house has helped the company add revenue and staff while also improving the control of delivery schedules and customer costs.
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 inch) in 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 set up 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.”
Whayne has rebuild centers in Louisville and Corbin Kentucky where all exchange/re-sell goods are processed. The hydraulics shop in Corbin has eight cylinder technicians three full-time machinists three pump experts plus a foreman and service coordinator. The Corbin operation added a machine shop to its hydraulics shop in 2009 that included 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. The shop has five cylinder service bays one for suspension cylinders one for lift cylinders on small loaders and three for high-force cylinders.