In Harley's 'Hog heaven,' keeping tidy is a big job.

Chip handling/coolant reclamation system up to the task.

In "Hog heaven," machining chips accumulate at a hellacious rate--as much as 3000 lb a day.

For the motorcycle manufacturer Harley Davidson Motor Go, celebrated for such heavyweight "Hogs" as the Softtail and the Electra Glide, those chips are a necessary evil. At its Pilgrim Road powertrain plant in Menomonee Fall, WI, they're part of the price for producing the new Twin Cam 88 "Fat" Head engine and the standard Evolution V-twin series.

As if that weren't enough of a systems engineering challenge, this housekeeping task must fit into a larger corporate strategy called Plan 2003. Kicked off in 1996, the strategy aims at doubling its manufacturing capacity by the company's 100th anniversary in 2003. In effect, Plan 2003 is the capstone of the manufacturer's almost-legendary comeback that began nearly 20 years ago.

In the Pilgrim Road section of Hog heaven, manufacturing engineer Eric Rhodes has a simple yet daunting tactical mandate: produce more motorcycles while improving efficiency. Accordingly, Mr Rhodes relies on a machining line every bit as robust as any Harley Hog. It's a machining cell with six Okuma MC 500 horizontal machining centers, a Witzig & Frank Turmatic Triflex machining system, and a combination machining/assembly system, plus a WesTech conveyor line.

Faster than you can say "Motorcycle Mama," a powerful manufacturing cell like that can be firing chips. So Mr Rhodes and Harley Davidson have looked to Mayfran Int'l, Cleveland, OH, to keep things tidy in Hog heaven. Part of the H-D machining strategy is Mayfran's Viavent, an overhead system that transports chips and coolant from all eight machining stations to a central separation and filter unit.

Part of the plan

"The Viavent system has answered all of our requirements and concerns as set forth by the Plan 2003 guidelines," Mr Rhodes says. "First, it is installed above floor, so that there's little chance of ground and environment contamination. Plus, there was no need to tear up existing floors for storage tanks and trenches to route piping. Being overhead, we can easily modify or add on to the system as future requirements may warrant. Because the system eliminates individual chip conveyors, hoppers, and filters at each machine, the floor layout of the cylinder head line is more compact, making it easier for cell attendants to move from one machine to the next, loading and unloading parts. Also, the system is closed-loop, so there's minimal coolant mist in the air."

According to the company, the system enhances machining quality. The coolant is filtered to a 10[micro]m particle size or less using a main filter unit, and a secondary cleaning tank helps maintain a better finish on parts. Mr Rhodes adds: "Also considered in the selection of the Viavent system is the fact that a single chip hopper instead of eight, is more easily monitored and removed when full. There are fewer moving parts or mechanical devices, making it virtually maintenance-free. Energy consumption is approximately no more than if each machine had independent chip handling."

How it works

Viavent is proving to be powerfully simple and simply powerful. At each of the machines within the cell is a compact pump station housed in a small holding tank. At this point the pump station and all pipes are at floor level. Harley-Davidson installed a wire screen platform around the cell, covering the pipes and pump and creating an ergonomically sound height for attendants to load and unload each machine. Chips, strings, fines, and coolant are directed from the machines' beds to these stations, where they are then pumped through a vertical rise discharge pipe of 2" dia and flow into a horizontal pipe run of initially 5" dia. This horizontal run is routed in the roof trusses. With other connections from the various machines, it moves until it descends to the central chip separation unit and dual filters. As the additional pipes join the run, the pipe's diameter is increased to 6" and finally to an 8" dia size.

At predetermined time intervals, the Viavent PLC signals a foot or discharge valve near the separator/filter unit to close. That allows the system's pipes to fill with coolant. Once the correct coolant level is reached, another signal okays the opening of both the discharge valve and the valves located in control vessels mounted at the system's highest point. A siphon effect then flushes coolant, chips, and sediment through the pipes and to the filter unit.

Mayfran zone manager Ken Angie says this system's relatively simple "flush" eliminates the need for high volume, energy-consuming pumps to clean out the lines. "The flush cycle," he adds, "eliminates the potential for coolant to accumulate in low areas and become contaminated. Based on the output of the machining cell at Harley-Davidson, the cycle time for this flush operation is about every 20 minutes."

Mayfran, however, did have to consider the output of the Turmatic Triflex machine. As it processed cylinder heads in Hog heaven, what type of chip would result? Mayfran studied the machine carefully, and added space in its system to include the integration of a chip-shredding unit if necessary So far, H-D hasn't needed to use this backup plan.

With the head line still moving toward full production levels, Harley-Davidson is looking for an additional benefit from the Viavent system. Previous installations of this system have cut energy consumption 20% to 40% compared with conventional in-ground systems.