The assembly line at Power Curbers (Salisbury, N.C.) shapes steel into more than 1,000 different parts for the products the company has been turning out, and improving, for more than 54 years. Among other items, the company provides machinery for the extruding and on-site molding of concrete (known in the industry as slipforming) for curbing and sidewalks. Power Curbers equipment is used all over the world—in 80 countries to date.
When the 85 employees moved into a larger manufacturing plant in last summer, most got their first look at a unique, labor-saving system. Designed by Mark Vanhoy, the company’s project engineer, with the help of Bill Miller, a company fabricator, and built by Miller, welder Chris Evans and mold line supervisor Walter Pence, the creation had been in the works for more than a year.
The new system is at the beginning of the assembly line. It’s a series of three parallel roller beds between the plant’s three metal saws and a new six-foot-high storage rack that holds, in 197 shelf compartments, 197 different-shaped lengths of steel (bars, angles, round tubing, square tubing, etc.). These are all roughly 20 feet long but can weigh from 50 to 1,500 pounds.
The ergonomic system streamlines the transfer of the steel to the saws, where it is clamped in place and cut into shorter pieces that become parts as they are milled, welded, turned and coated farther down the line. Mounted on lift tables, the roller beds can hold up to six lengths of steel at a time. In keeping with the company’s passion for lean manufacturing practices, the system significantly reduces the labor required to just one employee.
As a bonus, the new procedure is safer than the way the saw had been fed at the old plant. The old method required employees to lift as much as 10,000 pounds of steel in a single day, dragging each piece from its roller-less shelf, hooking it onto a cable hanging from an overhead crane, balancing it to minimize tipping, then grappling with it to bring it into position at the saw, where it was clamped in place for cutting.
Two of the new roller beds can be independently moved vertically and horizontally, to line up in front of particular shelves. They are bolted to long, narrow lift tables that provide vertical movement.
|At the beginning of the assembly line, a rack of compartments (background, to left) stores lengths of steel from which various parts will be fabricated. To transfer the steel, the company uses one stationary roller bed (background, to right) and two long, narrow Southworth scissor-lift tables that can be moved horizontally as well as vertically.|
These are manufactured by Southworth Products (Portland, Maine).
“We’ve had Southworth lift tables for years, and they work very well,” says Vanhoy. “They come in handy for so many tasks; they’ve saved us a lot of back strain on our assembly line, and they’re built to last, so naturally, I thought of Southworth first.”
How it Works
Vanhoy chose two Southworth Model LST4-48 tandem lifts, which are designed to provide level rise for long loads, such as lumber, pipes, bar stock, etc. Supported by two electric/hydraulic scissor-leg assemblies, each 24-by-168-inch platform is raised and lowered with the flip of a switch. Each has a capacity of 4,000 pounds. The required three-phase power feed is 460 volts.
Each Southworth lift is bolted to the top of a welded, 2,000-pound frame that rises about one-quarter inch off the floor when a large air bag is inflated with compressed air. For horizontal movement, Vanhoy’s system uses linear bearings, a Thompson rod and a servo-control motorized (single-phase, 115 volts) drive wheel to move the whole structure, which rides a rail at one end to keep it perpendicular to the storage rack. The inflated airbag slides along a wide strip of sheet metal built into the floor.
To pick the right piece of steel from the rack, the operator uses a single control panel to move the platform into position in front of the right shelf. Then he or she grabs the required piece and pulls it across the rollers to the saw. Because the floor of every storage compartment is also a roller bed, a single person can move even the heaviest lengths of steel. The whole system contains 18,000 rollers.
The new system has eliminated most of the lifting and walking that was needed at the old plant to bring the steel to the saw. Vanhoy estimates the labor savings at three hours for every eight-hour shift—a reduction of more than 35% for the operation.
For more information, visit www.southworthproducts. com or www.powercurbers.com.