Lean Manufacturing 101
In today’s highly competitive trailer market, it is more important than ever to improve quality, cut cost, and reduce lead-times. One of the most effective tools to accomplish all three of these objectives is Lean Manufacturing (lean). Lean is not rocket science, it’s just good common sense with a few tools and guidelines to follow. Henry Ford was practicing lean manufacturing in the twenties, long before the Toyota Production System became popular in the eighties.
The crux of lean is the identification and elimination of waste or “Muda” the Japanese word for waste. Since most of the literature on Lean Manufacturing was developed in Japan by
Shigeo Shingo and Taiichi Ohno, lean jargon often uses Japanese terminology.
All systems contain waste, and eliminating waste can create a significant competitive edge for a company. However, each system is unique and will require a different order and application of lean tools to be effective. The type of industry, the company, and the culture all influence the tools and processes that will work best for a company. There is no need to use every tool in the lean toolbox to be successful. Use those that work best for your company and leave the rest in the toolbox until you need them.
While there are eight wastes identified by lean manufacturing, there are seven wastes created in trailer manufacturing facilities in particular: overproduction, inventory, waiting, motion, transportation, rework, and over processing.
Ideally, companies should only produce just what the customer wants when the customer wants it. Overproduction is a waste of resources, both material and labor. Often, companies cite
economies of scale to justify building to stock. Once you examine the cost of overproduction, it may change your mind. There is the cost of materials and labor that is sitting in inventory. Yes, it’s an asset, but it also ties-up cash. Moreover, there are numerous overhead costs associated with inventory, taxes, administrative cost, the cost of handling, damage, obsolescence and so on.
Inventory is any raw material or work in progress that is not having value added to it. If there are 10 trailers waiting to go into paint, then that is considered inventory and thus a waste. This
is generally caused by poor level loading, or in Japanese terms, Takt Time. This simply means that the complete manufacturing process should be broken down into equal processing times based on final product demand. This will help ensure that all trailers are in the process. Example: If you need to produce ten trailers a day, and there are six steps in the process, each step should be equal in time. Inventory can also be driven by the first type of waste: overproduction. Ideally, you want inventory to be as low as possible. This can be accomplished by establishing a pull system of manufacturing and partnering with suppliers to deliver only as
needed. Another option is vendor-managed inventory (VMI). This is where the vendor has the inventory on site and your company is not billed until you use it
Workers waiting on materials or the previous process to be completed is a sign of poor process leveling or poor quality. At fault, could be the “Takt Time” – the amount of time required to meet the demands of the customer. Again, your company should aim to set up each step in the process to have the same Takt Time. This will ensure you maintain minimum work in process and maintain optimum efficiency. The objective is to create flow in the process. The simplest example of flow is when each step in the process has the same Takt Time thus there is no work in process waiting.
Example: Step 1. Cut materials for trailer frame 1 hour. Step 2. Weld trailer frame, 1 hour. Step 3. Hang axles and lights, 1 hour. Step 4. Paint trailer, 1 hour. While this is an over simplified example, it explains the goal of dividing each process into equally timed sections. Try to level the process times as closely as possible to create flow. Additionally, you can add processes to steps or move people to help complete the section in order to even out the time of all processes. For example: if cutting the materials only takes 30 minutes, then send that operator to another task for 30 minutes or combine operations in order for the entire step to equal 1 hour.
Unnecessary movement of people, parts or tools within a process is referred to as “Muda”. If a welder has to stop welding for 10 minutes while he goes to the stockroom for wire, that is waste resulting from motion and is non-value-added time. For example, to rectify the waste from additional motion, the rolls of wire should be stored at the point-of-use. Where practical, parts/ supplies should be stocked where they will be used.
Unnecessary movement of people or parts between processes results in waste stemming from transportation. If the press brake making the axle hangers are 300 feet away from where they are installed, the press brake should be moved to where the parts can be fed directly to the point-of-use, preferably managed by a Kanban. Kanban is a pull scheduling system for lean and just-in-time manufacturing (JIT). If the brake press makes parts for various other areas, this may not be practical but parts can still be on a pull system (Kanban) to avoid overproduction.
However, machines that feed one process should be placed to eliminate transportation.
The old saying, “If you don’t have time to do it right, where will you find the time to rework it?” rings true in lean manufacturing. The cost of quality can be staggering compared to Poka-Yoking the processes and tools. Poka-Yoke is a Japanese term that means “mistake-proofing.” The charging cord on your phone is a good example of a Poka Yoked tool. You can only insert the plug one way. You could not do it wrong if you wanted to. You should always try to design processes and tools in such a way that you cannot do it wrong.
Producing beyond the required standard creates waste. Over processing can be minimized with detailed work instructions. For example, if the specification is for all sharp edges to be deburred, but the employee is putting a radius on the part, this results in over processing. This is an example of adding cost, not value. Keep in mind that value is what the customer is willing
to pay for. Everyone should ask themselves at every step within a process, “Does this add value or is this a non-value-added step?” Value added would be putting the coupler on the trailer. The customer is willing to pay for the coupler to be installed so it is value added. The cost of reworking the coupler or going to the stockroom to get the coupler are all non-value added. The customer does not want to pay for mistakes or unnecessary movement. The customer only wants to pay for installing the coupler. When practicing lean manufacturing, aim to eliminate or minimize any action that does not add value to the product.
Lean is a journey that continues every day for as long as the business operates. In summary, it is important to remember the objective of lean is to eliminate waste and to add value for the customer. Anything that the customer is not willing to pay for is waste, including rework, inventory, set-up, waiting, etc.
The following are recommendations to start the process of lean manufacturing in your factory:
Step 1. Institute the 5S system in all work areas. 5S is a method of workplace organization and visual controls. The five S’s are:
1. Sort: separate needed tools, parts, and instructions from unneeded materials. Only have the needed tools and materials at the work station.
2. Set-in-Order: neatly arrange and identify parts and tools for ease of use.
3. Shine: conduct a cleanup campaign.
4. Standardize: maintain the first three pillars of sort, set-in-order, and shine activities at frequent intervals to maintain an effective workplace in perfect condition.
5. Sustain: form the habit of always following the first four steps.
A clean and organized workplace will improve the quality of workmanship and drive improved efficiency. People tend to adapt to their environment. If the environment is dirty, unorganized
and inefficient, the final product will be too. If the environment is clean, organized and efficient, it will be reflected in the product. A clean and organized workplace also improves morale and attendance.
Step 2. Create a current state value-stream map which is a simple diagram of every step involved in the material and information flows needed to bring a product from order to delivery. Once you have mapped every step, you can start identifying opportunities for elimination of waste (Muda). Every step needs to be verified and timed to develop an accurate current state map.
Step 3. Look for current possible opportunities to eliminate waste. Once you have located opportunities, start the corrective action process. If it’s simple, just have the employee/supervisor do it. If it requires more research and planning, hold a Kaizen event to address the issue. Kaizen events are short-term brainstorming to support continuous improvement. Hosting a Kaizen event can be accomplished by bringing together teams or individuals to brainstorm or introduce process improvements. Workshops should consist of representatives from all stakeholders. Empowering employees is the most effective way to identify waste and increase buy-in. To start, ask employees their recommendations on how improvements can be made. Start a contest where you reward employees for ideas. Employees
that feel they have a say in how the company is run are more motivated to see the company succeed. For more information with ideas on how to conduct continuous improvement, checkout The Idea Generator by Norman Bodek.
Step 4. Use the 5 Whys when evaluating problems. The 5 Whys is an analysis tool for problem-solving and will help identify the root cause of waste. The goal is to ask “Why?” five times
in order to dig deep enough to find the actual root cause, not just a symptom of that cause. For example: a purchase part was late because the supplier did not have needed lead time. Why?
The requirement was loaded late. Why? The drawing was revised, because the part could not be manufactured. Why? The engineer did not verify manufacturability. The corrective action is to create standard work by adding a spot on the drawing for manufacturing to verify and sign off manufacturability before the drawing is released. In addition to helping find the root cause, the 5 Whys exercise clearly shows cause-and-effect within the problem.
Step 5. Take the Gemba walk. Gemba simply refers to the location where value is created. Management should take a walk around the area where value is being created and observe the processes looking for waste. Take notes of what you see and ask questions. If you question a step or a process, go back to the 5 Whys. Fresh eyes will often see things that those who have become accustomed to the process may not observe.
Step 6. Employees tend to focus on what their bosses emphasize and monitor. It is important for employers instituting lean manufacturing to set goals and create metrics. These metrics should be posted in each area and updated at least weekly, while daily is better. Common metrics for manufacturing are quality, production, safety, and cost. Make goals SMART: specific, measurable, attainable, relevant, and time-bound.
These are just a few of the tools used in Lean Manufacturing. Lean is a continuous process of eliminating waste. In order to become and sustain a world-class facility, everyone within the organization must be practicing lean every day. Lean is a journey, not a destination. For more information about instituting lean into your business, check out The Toyota Way by Jeffrey Liker and The Goal by E. Goldratt and J. Cox.
About the Author
Steve Starnes is the CEO of Superior Trailers LLC located in Whitesboro, Texas. Starnes has an MBA, Six Sigma Black Belt and 40 years of manufacturing experience and hopes to encourage members of NATM to institute lean manufacturing practices in their facilities. Superior Trailers LLC is a locally owned trailer dealer, full-service repair shop, and manufacturer that carries a full line of new and used horse, cattle, utility, dump, and car hauler trailers from major manufacturers. For more information about his company, visit www.superiortrailersllc.com.