Waste is fairly common in woodshops. And one way to keep it in check is a concept borrowed from the auto industry. Lean manufacturing began in the 1980s at companies such as Toyota, but it has evolved so much that credit for its current form is questionable. So, too, in the opinions of many traditional managers, are its benefits. But it keeps on growing in popularity, so perhaps it’s worth a closer look.
The large industrial concept of lean manufacturing is that, by eliminating waste, the production cycle can be shortened. Waste is defined in many ways and can include any work or activity that is not directly related to the production of a finished product. It can also include a strong focus on reducing a company’s inventory of raw materials, thereby reducing the amount of cash tied up in, for example, plywood sheets, and also the physical space used to store them. That extra space needs to be heated, cleaned, rented, maintained etc., so it adds to the bottom line.
Thinking in such comprehensive, all-inclusive ways about each activity or asset can decrease the amount of time spent on every cabinet or piece of furniture that is made in the shop. It can significantly improve profit margins, make customers happier (less waiting) and even make employees more satisfied — and even more productive.
One of the keys to lean production is that components are only made in-house to order. That is, there’s no stash of drawer sides in a dark corner somewhere, waiting for future kitchens. Third-party elements such as drawer slides, outsourced components and spray finishes are only purchased and brought in when they will be fully consumed by current production (called “Just-in-time” or JIT purchasing). Production methods are streamlined so that the shop can switch from cutting to assembly to finishing and do so with a minimum of downtime. Tool inventories are reduced. For example, two woodworkers can use the same collection of pneumatic tools that are stored on a cart that sits between their two workstations, saving cost and space.
Other examples of lean are more personal. Staff members are trained to excel in more than one phase of production so nobody ever has slow periods or has to wait for somebody else to catch up. They can jump in where needed. An essential element here is that employees are given enough autonomy to see that need and go fill it. Training is essential, too. The better people are trained, the fewer defects have to be addressed. Reducing wasted time is as important as reducing inventory.
One of the biggest stumbling blocks in lean inventory management is that, as a shop is now buying only what it needs immediately, some bulk discounts are imperiled.
Just-in-time ordering can backfire in a hurry, too. When a crew becomes overly eager to reduce their inventory stockpile to almost zero, any glitch in delivery can derail the entire production process. Imagine having six guys standing around waiting for the UPS truck.
Software helps, especially when it tracks patterns and makes predictions based on historic usage. Sometimes, zero isn’t the most efficient goal and prediction programs in the computer can often shine some light on that. They look at the last quarter, or perhaps even a whole year, and establish a very lean minimum (a single kitchen worth of drawer slides) that is absolutely necessary. While the purest concept in lean production is that “inventory is waste,” that might be more true for large industrial manufacturers such as GM or Ford who can often switch to another production line, than it is for small shops that only build one job at a time.
Some of the more experienced people on the shop floor often resist a new movement toward lean manufacturing. Craftsmen and women who have spent most of their working lives nailing down patterns and procedures are often reluctant to change or share their station with another employee or take on new tasks and training so that they can be flexible enough to help out where they are most needed.
To combat such reluctance, management needs to institute a companywide commitment to lean processes. Doing it in one department isn’t enough. The system rarely works well when adopted in one area and not another. A sense of teamwork is at the core of the philosophy and, if everyone isn’t on board, high levels of waste (especially time) will continue to exist.
Lean manufacturing is, by its nature, designed to take advantage of repetitive, continuous processes. If a shop essentially builds the same cabinet boxes over and over again, it’s a much better candidate for a total overhaul than a custom shop that makes unique architectural elements one at a time.
The obvious upside to implementing a successful lean process is that costs are cut. That’s due to better handling of materials, less money tied up in inventory and the space it uses and also the people who buy and manage it. But companies who act as a team to implement a lean regimen also see some subtle benefits such as better quality control, better customer service and higher morale on the shop floor. Even incidental events such as downtime from injuries or guys calling in sick on good fishing days are affected when employees have achievable, individual goals that contribute to the team’s performance. That personal ownership of the job often comes when management asks people to help study the number of steps in each process they perform and then listens to shop-floor suggestions designed to reduce processes to their essence.
Lean production in the wood industry, and especially among shops with more than one or two employees, is about creating teams, reducing setup times, building specialty (cell) groups who handle specific tasks and attain high levels of skill, implementing pull scheduling (that is, every task is based on a customer’s needs) and something called six sigma. This is the concept that defects can be identified and their causes eliminated before they slow down the process too much. It was developed by Motorola USA in the mid-1980s and has become a watchword in many different industries. It works by creating databases of possible defects and extrapolating statistics from them. Specific team members then follow a defined sequence of actions to reduce or eliminate the defects, using these data. For example, if every right-hand pull on every pair of double doors was 1/8” lower than the left one, there would be a procedure in place to check sequentially for causes, beginning with the most obvious and working down from there. And a designated team member would follow that list, rather than having four guys meet in the loading bay to spend a half-hour discussing it.
As with any school of thought, lean manufacturing has its own lexicon. We’ve already come across a few of the terms (Just-in-time, six sigma), but there are many more. Kanban is a visual aid that triggers an action. For example, when the drawer slides on the shelf get down to, say, two dozen, there might be a cardboard sign inserted there that tells the supervisor to order more right away.
Kanban can also refer to reorganizing or re-engineering the shop based on workflow. For example, maybe all the wide belt sanders don’t need to be located close to the central dust collector. Perhaps the shop can be organized according to the continuous flow of parts, rather than by designating space according to function. Several small dust collectors might be able to each serve a distinct sander that is now located at the end of a different production line (one each for doors, face frames, drawer fronts, etc.). Is it more efficient for employees to load a cart and bring the parts to the sanding room or to have a sander right beside them when the parts come out of the glue press?
“Pull” production is a large part of lean manufacturing. This essentially means that production is driven by direct and immediate customer demand. If a company builds six panel doors for three major home stores, not a single door would be manufactured until an order is in hand, even though there is enough history to predict demand fairly accurately. The idea here is that no shop space, no inventory of parts, no employee time is invested until the cash to cover them is rolling in.
A “two-bin system” is one element of pull production. Put simply, components are brought to the workstation in, well, two bins. As one is being emptied, the other is being filled. For example, a team member might bring a pallet of Baltic birch to the panel saw and, while that supply is being cut up, the same forklift operator will have taken the last (empty) pallet back to the loading dock and start loading it up so it’s ready to be delivered as soon as needed. The key here is that the two tasks are matched: it must take less time to supply the parts than it does to cut them in order to avoid downtime. The relationship can be regulated by, among other things, the number of sheets on a pallet. It’s pretty simple stuff — and that’s the magic of lean manufacturing. Each task on its own is a simple, precise, waste-free element, but when they are combined, they form a sophisticated, complex, comprehensive system.
Heijunka is a concept borrowed directly from Toyota. The Japanese word means “production smoothing.” When the system in a shop is lean down to the point where everything operates on supply and demand (no backup inventory), then the process is vulnerable to fluctuation. To smooth out the kinks, a shop can either level demand (perhaps by rescheduling deliveries with customers) or level supply (production). What Toyota does is it mixes up the different car models coming off the production line, so if there’s a huge demand for Tundras when the snow flies or a surge in Prius orders when gas prices go up, they can tweak the line to match those fluctuations. In the woodshop, processing two or three kitchens simultaneously would theoretically allow the team to switch from one job to another if, for example, a plumber or a painter caused an install delay on one kitchen.
A Kaizen blitz or event is a quick reaction to change in the production process. It might involve immediate changes to the personnel in a team or new setups or processes that improve workflow immediately and often temporarily. In general it refers to a small-scale change, rather than a full systemic change — part of the process is revamped, rather than a shopwide shift occurring. The concept is that a lot of resources are made available to a small segment of the system and this concentrated effort can result in a minor change that has major impact. A Kaizen event generally begins with an analysis of a process, followed by some engineering or design work, and then the staff are trained and ready to go before a production zone or workstation is very quickly reorganized or rearranged. Often, an efficiency expert will choreograph the whole thing, the event happens in a single day or perhaps over a weekend or even during the night, and downtime is minimized.
For woodshop managers interesting in exploring the possibilities of lean manufacturing, the best advice seems to be “think slowly and act quickly.” Take a long, hard look at how each process is managed on the floor and, rather than attack problems piecemeal, see how each workstation interacts with the next before making any changes. Production is subject to the domino effect: if one piece falls, they might all fall. The experts all agree that lean processes only work when the entire production system is integrated. If changes are to be made, they should be completely worked out on paper before they are implemented. And the consensus is that the people who are actually doing the work often make the best suggestions as to how their particular part of the process can become, well, leaner.
This article originally appeared in the May 2012 issue.