June 4, 2009
Equipment manufacturer streamlines part flow and drastically reduces WIP and raw stock inventory. Once a part hits the floor, it never goes onto a rack.
Three fingers. Thanks to a custom material handling system, that's all it takes one fabricator just north of Charlotte to move thousands of pounds of steel a day.
Everyone at Power Curbers Inc., a manufacturer of curb-making equipment in Salisbury, N.C., practices lean thinking with gusto. The company carries no raw-stock or finished-product inventory—none, zippo, nada—and has achieved single-piece part flow; employees work on just one machine at a time.
One machine's worth of material comes into the loading dock, is sent through manufacturing cells that run in a U down and back up the 45,000-square-foot facility, and a finished machine leaves on a truck at the same loading dock. It takes seven days for raw material to make the trip through the plant, and the company finishes a machine every three days. Plantwide, Power Curbers turns inventory 12 times a year; for one principal value stream, managers estimate they turn inventory 25 times a year.
Company leaders have put their focus on takt time and worker safety. In their eyes, lean is about moving quality parts through the floor as quickly, easily, and safely as possible, and employees shouldn't break their backs doing it.
Vice President Craig Neuhardt reaches into a rack with 18-foot-long cubbyholes floored with rollers. Using only three fingers, he slides a rectangular tube weighing hundreds of pounds onto a scissor-lift table, which in turn moves vertically and horizontally to feed the tube directly into the band saws (see Figure 1)—no manual lifting, crowbars, or forklifts required.
"There are 19,000 rollers on this rack," explained Randy Ward, shop supervisor. "Anybody can take a 600- to 800-pound steel tube or barstock and slide it over to the saw."
Behind this rack and next to the loading dock is, well, nothing: no rack of plate inventory, no tube or barstock. "We expense this material as we receive it rather than turn it into capitalized inventory," Neuhardt explained.
The shop can do this because the material for one machine goes from the delivery truck right into production. The tube and barstock go directly into the ball-bearing rack, ready to be moved to the band saw. Cold-rolled flat steel from 16 gauge to 1 inch thick comes in pallets stacked in the order they will be cut on the plasma tables.
Ward then points to the plasma operator who is using one of the plant's 34 overhead cranes to place a sheet onto the plasma table. Cut parts are then placed on a wheeled cart. "If a part isn't on a machine, it's on wheels. From the time it comes in the door, to the time it leaves, it never goes on a rack."
He isn't kidding. The plasma operator wheels parts over to deburring and bending (see Figure 2), finally to meet up with cut and machined tube and barstock. Then, it's on to welding (see Figure 3). Each cell has everything a welder needs to assemble machine subcomponents, including wire welding, a turning lathe, and other machinery. Fixtures are set up for optimum ergonomics, and fixtures themselves are even on wheels, so they can be moved between welding cells if needed.
After welding, the fabricated subassemblies and components are put on what the company calls paint buggies, which carry components through final assembly. According to company managers, the buggies have been key to the company's lean transformation.
The buggies resemble vehicles used at airports that take luggage out to the airplane. Each buggy hangs parts vertically, so they don't need wide aisles to move material. A water spider (the plant's designated person who responds to material needs) drives a tugger to pull one buggy or a train of buggies from the welding cells to an area where parts are power-washed with specially controlled chemicals to ensure a consistent paint finish. Again, the parts stay on the buggy (see Figure 4 and Figure 5).
Then the water spider hops on the tugger and pulls the buggies into the paint booth. To keep consistent flow, and make sure nothing gets misplaced, everything assemblers need to put together a finished machine stays on the buggies in specific places and in a specific order. Parts that don't require paint are placed in sealed containers on the buggy.
The buggies also serve another purpose. "It's gotten us out of the habit of making a few extra parts, just in case," Neuhardt said. The buggies have room for needed parts and nothing more.
The buggies have certainly proven their worth. Managers estimated that workers previously spent about 1,000 hours a year sitting on a forklift, moving material. To put that in perspective, "That's equivalent to having two and a half guys doing nothing but sitting on a fork truck all year," Neuhardt said. Today one forklift and two tuggers pulling paint buggies altogether spend about 50 hours a month moving material.
After painting and drying, the parts spend their final three days in assembly. The workers build components around the engine, cooling, and hydraulic systems, which are brought in by an outside supplier.
The company outsources surprisingly little, in fact. "At one point we outsourced [the fabrication of] three-quarters of the machine, and it would come in as a kit," Neuhardt explained, adding that as the company became leaner, it filled freed-up floor space with additional processes.
The decision to outsource depends on the product, market, and company, and some lean OEMs outsource all but a few core competencies. At Power Curbers, it was the mold part of the business, among other things, that drove managers to bring almost all welding, cutting, and bending in-house.
Molds make up Power Curbers' most job shoplike value stream. The mold is the component on every curb-making machine that actually shapes the curb, highway median, or similar structure. Every local government has different rules on curb height, sidewalk widths, and the like, so almost every mold that attaches to the bottom of a curb-making machine is different.
Such custom fabrication has to be in-house, so "we've always had to run a shop," Neuhardt said. "That means we need to employ a certain number of people, we need to have compressors, we need shop supervision, so why not make as many parts in this space as we can, and spread that overhead over more items?"
At the plant entrance are several rows of plastic kanban bins holding various components, grouped by colors representing value streams. Managers say this inventory is unavoidable to meet customer demand, especially in the parts department. The company guarantees any machine built in the past 15 years will have spare parts available within 24 hours. "This means we have to carry a little higher inventory here than what you might expect for a lean organization," Neuhardt said. "But on the other side of that, we never put a customer down anyplace in the world."
This limited inventory follows a simple order replenishment system—no reports, no unnecessary paperwork. When the bins are emptied to a certain "safety stock" level, a worker simply removes a card, complete with part number and a simple drawing of that part, and places it in a basket for each value stream, signaling either the company to order parts from an outside vendor or build additional parts in-house (see Figure 6).
The color schemes of those kanban bins are a part of the company's visual management strategy. Bins labeled yellow represent components for the machine body; blue for mold production; green for aftermarket parts; and red for R&D and special products. This color scheme carries through the fabrication department, as yellow, blue, green, and red carts are transported between operations.
To minimize bottlenecks, shared resources are kept to an absolute minimum. The company has three plasma tables, for instance, one for each major value stream. Half the machines may be sitting idle, even in good times—something that may be an eyebrow-raising sight to someone accustomed to batch manufacturing. If a machine isn't running, it isn't making money, right?
As company President Dyke Messinger recalled, "Showing that machine utilization wasn't important was perhaps the biggest transition for our manufacturing people."
Power Curbers brought in several lean consultants to get where it is today. One of them, Brian Maskell of Cherry Hill, N.J.-based BMA Inc., put the issue of machine utilization in perspective. The question shouldn't be about machinery utilization, but "how fast the product flows through the factory."
One of the basic functions of any business is to shorten the time from receiving an order to getting cash for it. So it doesn't matter if a machine runs 24/7 if it takes forever and a day for a product to ship to the customer. This, said sources, is why visual management is so important, and colored carts and paint buggies are an integral part. A machine sitting idle may not be a problem; but if a bunch of carts or paint buggies are idling in an area for an extended period, full of parts not being worked on—now there's a problem.
Messinger began learning about lean practices during the mid-1990s, and the company has trekked the continuous improvement path ever since. But lean hasn't eliminated all of the company's troubles. Because curb-making machinery is closely tied to the struggling construction sector, Power Curbers saw its volume decline so dramatically that it had to make some painful choices. The manufacturer recently laid off a portion of its work force, which today consists of 85 people across several divisions.
But there are bright spots on the horizon, Messinger said, adding that without lean manufacturing, the company truly would be in dire straits. Ultimately, he said, lean thinking will help the company emerge stronger once the economy recovers.
Power Curbers has been on the lean pathfor years, and it took more than innovative material handling to stay on the path.
Eliminate Product Lines. This, perhaps more than anything else, shifted continuous improvement into high gear. Company President Dyke Messinger admitted this took a big leap of faith, because eliminating these products dropped company revenue by several million. But the product lines involved parts and processes so different from its higher-volume lines that they made the entire operation more complex and less efficient. Today the company focuses on product lines that flow through just a few value streams and works to continually reduce takt time, lower costs, increase margins, and, ultimately, make the entire business more profitable.
Make It Visual. The company's pulse can be seen on just two whiteboards. One, posted in the front office, shows the status of outstanding orders, tracking the time between receiving an order and the final payment after delivery. In the manufacturing conference room is a second whiteboard that tracks production issues, something the company does in a remarkably simple, efficient way.
All employees are given cards, one that says "I'm working on" and another that says "I need help with." On the "I'm working on" card, the employee posts just outside his workcell specific items he's trying to improve within his own area. The "I need help with" card, which involves issues the worker can't solve on his own, is placed on the whiteboard so that all employees, from the company president on down, can attempt to address them (see photo).
Document Procedures. In the washing and pretreatment area, prior to painting, is a detailed procedure, posted on the wall, showing exactly what chemical mixture to use when and the steps involved. Following lean, Power Curbers documents procedures religiously. Procedures may continually change as employees find a better way to complete their jobs, but those changes are documented, always.
Provide a Career Path for Hands-on Talent. Since adopting lean practices, Power Curbers has launched what it calls a "resource department" dedicated to continuous improvement. Department employees can, for instance, build custom material handling equipment to solve part flow issues. These employees rise from the production ranks and are cross-trained, which means they can fill in if a production worker calls in sick.
Fill Increased Capacity. As Power Curbers became leaner, it could produce more work in less space, so managers had some capacity to fill. Besides increasing sales volumes, they made strategic acquisitions that fit with their line of business. For instance, when Power Curbers acquired a company that made ancillary equipment used with Power Curbers' machines, managers used that acquisition to fill its freed capacity and floor space. Now those additional products are produced in a separate value stream (color-coded with orange kanban bins and carts) in Power Curbers' Salisbury, N.C., facility.
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