November 2, 2012
The issue for Laser Access employees wasn't getting the equipment running, it was the time they spent away from the machine, hunting for the right tools and material. That's why the Michigan shop took steps to keep the necessary tools nearby and neatly organized.
The people at Laser Access, a Grand Rapids, Mich., fabricator, know a thing or two about quick changeover. Launched in 1999, the high-mix, low-volume fabricator has spent the past decade perfecting the science of quick setup, with clear documentation and, at the shop’s five-axis laser cutting center, some quick-change tooling. The company started with just one five-axis laser; now it has two, plus one flat cutting laser with automated loading. Today the 22-person shop has expanded into arc and laser welding, as well as press brake work. Its customers range from those in the architectural industry to aerospace.
On the two TRUMPF five-axis cutting systems, the operator need only loosen and tighten four bolts to change out fixtures between jobs. The flat cutting laser, with its automated loading table, doesn’t take long to change over either. In fact, those setups are designed to occur in minutes, at least in theory.
But until recently, setups rarely took just minutes. It wasn’t because of poorly designed fixturing or machine problems, either. “We just weren’t effective at making sure the parts, the tools, and the paperwork were all staged and ready to go once the previous job was complete.” So said Jason Cunningham, shop foreman, who described how, because of such disorganization, the shop struggled to reduce process cycle time. The root causes of such disorganization involved seemingly mundane elements, including the placement of hand tools. “The little things matter,” he said.
Traditional lean manufacturing and other improvement methodologies promote efforts like 5S (sort, straighten, shine, standardize, sustain) that involve simple organization as well as placing tools near the point of use. Most workers at Laser Access have organized toolboxes at their workstation. But high-product-mix situations complicate matters. Not only is Laser Access a high-mix, low-volume shop, most of its work doesn’t involve repeat orders. The shop has longtime customers, but many of them don’t ask for the same job twice.
This means the product mix changes dramatically from one day to the next, so one tool may be used many places. Tools with consumables—say, hand grinders that regularly require abrasive media—complicate matters even further. A person at a grinding station may work with a standard 90-degree grinder for one part, then a narrow belt sander to grind some intricate shapes, and then back to a 90-degree grinder with a different-grit disc.
In this case, having every possible abrasive for every hand tool at the point of use would make an already complicated situation even more complex. With such highly variable demand, how would they efficiently manage inventory levels for that abrasive media?
This was the very question Laser Access managers asked about six years ago, when the company began informal continuous improvement efforts. “We do a lot of challenging stainless steel and aluminum jobs,” Cunningham said. “There are a lot of places that won’t cut this material.” The material does require deburring, though, and that’s why many parts coming off its 2-D laser cutting system flowed to the company’s grinding work centers.
Unfortunately, abrasive discs and similar consumables lay everywhere. Such disorganization increased work-in-process and lengthened overall manufacturing time. That’s because workers spent so much time hunting for the right abrasive media. “A lot of these are intricate jobs,” Cunningham said. “You just can’t put a 36-grit disc on and hog the material off.”
Sometimes the job would grind to a halt (pun intended) if a certain disc couldn’t be found. The purchaser placed a rush order for abrasive discs, and workers would move on to other jobs.
In this instance, centralized (not point-of-use) storage was the best option. The grinding and deburring area now has a centralized storage cabinet, where personnel can monitor consumable usage continually, and then request a replenishment order as the inventory of abrasive media reaches a certain point. By analyzing purchasing patterns over time, both the abrasive supplier and Laser Access could better predict when new abrasive media would be needed.
“We work with our local supplier on this,” Cunningham said. “They always have 500 pieces on hand, in case anything goes awry.”
The shop monitors abrasive inventory both at post-laser-cutting deburring and at postweld grinding. In the latter area, grinders hang on dedicated hooks; it’s a shadow board, just without the outlines. Each tool has a quick-release tool changeout system.
Until recently the blowgun also had a quick-release connection to the shop air line, which reflected the shop’s focus on flexibility. Sometimes workers in other areas needed the tool, so they borrowed it and often forgot to return it. This meant that postweld grinding operators had to go on a blowgun hunt, which certainly wasn’t value-added time.
That’s why a dedicated blowgun made sense for the postweld grinding area. Other machine workstations have their own air guns, and they still have quick-disconnect fittings. But in the postwelding grinding area, the air line now is permanently threaded onto the blowgun; someone would need to go through great effort to remove it. “Now there’s always a blowgun there,” Cunningham said. “It can’t walk away.”
This is about where Laser Access’ continuous improvement efforts stood when Cunningham and Quality Manager David Boland attended LeanFab, an event organized by the Fabricators & Manufacturers Association, held near Minneapolis earlier this year. At the time managers knew shop operations could improve, especially in upstream processes.
The conference, headed by consultant Dick Kallage, principal at Barrington, Ill.-based KDC & Associates, focused on the importance of flow and machine uptime. In high-mix, low-volume environments, setup matters. As Kallage put it during the event, “You’re not in the manufacturing business. You’re in the setup business.”
At Laser Access, excessive setup time certainly was an issue, and the problem occurred in a critical area: laser cutting. The changeover time at the machines—moving material, swapping fixture base plates, and downloading and running the program—took a few minutes. The problem was that operators spent a lot of time away from the machine, hunting for the right tools and material. This included simple tools, such as snips for cutting the straps around stacks of raw stock sheet metal.
Too often managers saw people leaving the forktruck to find tin snips; tape measure; or writing utensils to check material dimensions and fill out inspection, shipping, and receiving reports. To solve the problem, the shop permanently attached a small tool container to the fork truck. Now, wherever the fork truck goes, the tools the driver needs go with it (see Figure 1).
“So many times a driver would leave the truck to hunt for the tools he needed,” Cunningham said. “Silly little things like that really add up.”
Solving the raw stock inventory problems took more than a toolholder on a fork truck, though. For instance, under previous procedures, the purchaser ordered material as soon as the order was released. This meant material arrived well before it was actually needed. Now the shop releases orders for material shipments a day or two before they’re needed. The company also implemented a simple labeling system to identify different material grades and thicknesses in the raw stock racks.
Laser Access has a different procedure for sheet remnants too. Previously the operator removed the remnant from the cutting machine and transported it back to the raw material area, placing it into a 5- by 10-foot container that stored remnants flat in horizontal drawers (see Figure 2).
These were designed for a low-product-mix situation, where machines repeatedly ran the same material over and over, and this caused problems for Laser Access. The drawers separated remnants by material grade, but not thickness or size, and the sheets were all stacked flat. So if the next job called for a certain remnant, the operator needed to remove sheets stacked on top to get to it. “We sometimes needed to remove 15 drops of material, or even more, just to get to the material we needed,” Cunningham said.
Now remnant sheets are grouped by dimension and thickness. Most important, they are stored vertically, like a card file, so workers need only flip through to find the one they need before removing it with a lift crane (see Figure 3).
The operators also have a different process for removing remnants. After cutting, they place the remaining sheet on a wheeled rack, at which point they fill out the remnant information (grade, thickness, dimension, etc.) on the attached paperwork. This in turn is entered into an electronic file, which shows up immediately at the purchaser’s workstation in the front office. When ordering material, the purchaser now has an accurate rec-ord of available remnants. That means when he needs material, he orders only what is necessary, no more and no less.
All these efforts have improved the shop’s raw stock situation dramatically. And they have reduced on-hand raw stock inventory and increased machine uptime at those all-important laser cutting centers.
Cunningham was quick to point out that the improvement cycle isn’t finished. It never is, really. For instance, even with an organized, efficient deburring department, a manual operation can deburr only so much. That’s why the company plans to bring in a flat-part deburring machine to speed operations.
The fabricator recently had a problem with some laser consumable usage—specifically, a ceramic ring used on the five-axis system’s cutting head. As long as the laser is operated properly, the ceramic ring should last for a long time; it isn’t a high-wear component. “But we found a lot of our ceramics were disappearing,” Cunningham said.
That’s why managers recently installed a vending machine that holds ceramic rings along with other consumables, like lenses, nozzles, and safety glasses. Operators are given special coins with their initials on them. They drop these coins into the vending machine slot to receive a new ceramic ring or another consumable if they need it. “We can track who’s using those ceramics, so I have a source, and we can communicate with the operator. It just gives us better inventory control on our consumables.”
As Cunningham explained, the company’s lean transformation had to start with buy-in from the shop floor. Operators see the process every day and often have the best ideas to overcome problems. That’s why 5S and other improvement efforts continue today, unabated. Cunningham said that soon the company plans to implement a simple system of “idea cards.” If a worker sees a problem—a waste—and a potential solution, he simply writes the idea on a card and submits it for review. Cunningham added that this will be complemented by an employee recognition program.
Most important, workers are given the resources to improve, and here Cunningham pointed to an important new position on the shop floor: the spider. The name comes from “water strider” or “water spider,” which is lean manufacturing jargon for material handler. But at Laser Access, a spider is so much more. At the end of each day, the spider, who was promoted from within, stages work for the second shift and for several hours into the first shift the next day. In general, he stays several hours ahead, so that operators have everything they need—hand tools, fixtures, and material—exactly when they need it.
As Cunningham explained, the variability of a job shop brings with it various cycle times; it’s impossible to level-load such an operation. Many jobs are nonrepeat orders too. For those unique, never-run-before jobs, a process cycle time could be plus or minus so many minutes. Staging material several hours prior to the next operation provides a buffer to absorb that variability. The buffer doesn’t have days’ or weeks’ worth of material, just hours’, and those few short hours keep machines running and jobs flowing downstream.
The spider looks upstream as well. For instance, after the laser cutting operator loads remnant material onto the wheeled rack, the spider wheels the rack back to the storage area, enters remnant inventory information into the computer, and places the remnants back in storage. “This eliminated the waste of the operator putting the drop material into the rack,” Cunningham said. “That just adds to downtime on the machine.”
Organizational improvements like 5S and its clean workstations and shadow boards are essential. But by themselves, changeovers can occur only so fast, simply because the operator must retrieve material and the tools necessary to conduct the changeover. This, sources said, is why the spider’s role is so important.
`The spider’s day focuses on part flow, so he can see inefficiencies that others, especially those tied to specific departments, can’t. But the spider also makes everyone else’s job much easier. And when it comes to getting worker buy-in for continuous improvement, making jobs easier is a good starting point.
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