JIT – The Backbone of Lean Manufacturing

For many businesses, the biggest expense they face is inventory cost. The never ending struggle of having enough inventory to fulfill orders and leave room for growth while keeping enough cash on hand to meet any need they may meet is the number one cause for business failures, according to the Small Business Association. There are many ways around the skyrocketing costs of carrying a large amount of inventory, and a just in time, or JIT inventory management is one that can increase the business’s bottom line and return on investment.

The JIT inventory management strategy is one that is based on the idea that a business can order exactly the right amount of inventory necessary to fulfill their upcoming orders and not a single piece more. This reduces the cost of warehouse space, transportation costs, and other costs that can be reduced by this form of lean manufacturing.

The philosophy associated with this theory is that inventory is considered to be waste, and the lean process of JIT will eliminate that waste. By exposing the hidden causes of inventory, a set or series of signals can be developed that define what the company can use to measure and regulate the inventory necessary to meet the demand needs.

Identifying the signals that guide the inventory demand and calculating, harnessing, and predicting the same signals is at the core of the JIT system. Couple this with today’s modern day next day shipping capabilities, and you have a very capable JIT system. The signals necessary to make a JIT system successful are able to be generated with the modern UPC and online tracking systems. By tracking sales and the patterns that follow a business can plot the demand necessary, manufacture the products, and send them out next-day shipping. This model made famous by quite a few companies, but mostly by Dell computers, can greatly increase the quality as well as efficiency of a business.

A second aspect of JIT manufacturing is in the setup of the manufacturing plant. The workers, as well as the machines in the plant are oftentimes multifunctional, allowing flexibility in the plant’s ability to manufacture parts as necessary, independent of equipment or personnel status. With small lot sizes, this is the perfect setup for a dynamic, demand-driven supply chain.


Figure 1 - JIT - A fundamental lean manufacturing building blockAs can be seen in Figure (1), in a JIT system, customer orders are generated in a variety of ways. But each one of those ways generates a signal that is processed by the sales department, represented by the lightening bolts in the diagram. Many times, the sales department is nothing more than a remote server that is capable of taking and distributing orders in a JIT system. The necessary components and raw materials are calculated, and the signal is sent to the suppliers and the fabrication assembly to start manufacturing the product. As you can see, because each order generates a new signal, no inventory is incurred.

Dell computers is a perfect example of JIT manufacturing. By getting started in the business by manufacturing computers out of his dorm room, Michael Dell quickly learned that he could not spend all of his money on stockpiled parts and equipment. He decided that his computers would be designed exactly to the specifications to the customer, and his selling point would be along the same lines.

Without realizing it, his business was the perfect example of JIT manufacturing. His company was founded on the idea that any average person can log on to the internet, and with a little bit of assistance, can identify the parts necessary to build a computer from scratch. When the customer ordered the computer, Michael, in trying to come up with a solution for his dilemma of hot having any money or location to house all of the pieces needed to assemble a computer, stored a few few parts he would need to get the job done, then buy and manufacture new parts, jus as soon as the customer orders them. The raw materials are re-odered, sometimes automatically, and the end user gets a computer that they build online within 15 minutes!

Sometimes the end result effects are not always as perfect as planned. When Toytoa decided to shift to a JIT manufacturing process, they hit quite a few bumps in their process capability. The problem that Toyota found is one that will plague all JIT systems that do not make contingency plans for a quickly generated, unannounced increase in demand.

Since the entire supply chain system is built around the flexibility and speed of a company to respond to a demand, they do not have the ability to meet large quantity orders quickly. Normally, this is fine, since the large quantities can be forecasted by the signals generated and production increased to meet the demand.

However, sometimes demand rapidly increases without any significant explanation. Sometimes it is due to unplanned media coverage, and sometimes it is just due to the viral success of the product. Whatever the reason, the entire supply chain has to be redesigned and pushed to its capacity when one of these unexpected increases in demand shows.

JIT manufacturing was the wave of the future a few years ago, and while it has actually worked for some companies, most have unsuccessfully tried to implement it into their systems. In order to success, JIT manufacturing requires the perfect combination of speed, management, and product… something not many companies have. However, those that do find themselves on the receiving end of severe quality increases and cost decreases.

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Use Poka-Yoke to Rest Easy

The purpose of Six Sigma is to reduce defects to an acceptable level more consistently. This can be accomplished with a focused attention and everlasting drive toward improving the quality of the processes that are used during manufacturing and other aspects of the business. Ufortunately, even the most lean and highest quality processes have one unavoidable, detrimental flaw. We are only human, and mistakes will always be made. But there is hope, as there is a certain lean tool that may actually assist in removing the human error factor from the equation.

While it is impossible to completely eliminate the possibility of removing mistakes from the workplace, it can be possible to make the probability of them occurring so low, that they are virtually impossible. The technique of mistake proofing a process or workstation is called Poka-yoke, and is one of the most effective ways of reducing the number of defects over the course of time. The basic premise of the practice is that the process or conditions involved are designed in such a way that it is virtually impossible for a human, no matter what amount or training or background, to make a mistake when attempting to perform the task.

If the quality manager, or any manager for that manner, of a plant or process starts noticing an unexplained increase in the number of defects in a part of a process, the answer may lie in Poka-yoke. The best way to decide whether this tool may be the right answer for your team is to decide whether the flaws that are happening are due to a “careless error”, or tend to happen at times that are prone to lapses in judgment, such as Mondy mornings, the end of shifts, or Friday afternoons. While this isn’t a steadfast rule, experience shows that human errors occur at these times more frequently than others.

Another way to approach the decision to use Poka-yoke is by interviewing the workers themselves. Frequently they have anecdotes that outline how easy it is to make mistakes that can only be classified as mistakes. Additionally, you can audit your processes and identify certain elements that are critical to quality (CTQ), or have CTQ characteristics associated with them. These are perfect candidates for mistake proofing because a flaw in a CTQ can be detrimental to the entire product’s performance.

The key attribute behind mistake proofing is to keep the processes simple, and anticipate the locations in the process where the mistakes are most likely to happen. Then you can use methods like shaping tools and putting tools on lanyards so that the mistakes cannot happen without the blatant change of the tool’s function or scope.

Let’s use an example of a manufacturing plant that is piecing together a piece of electronic equipment to place onboard locomotives, as can be seen in the “before” section of Figure (1). The electronic piece of equipment has a cover that must be installed using a grounded screwdriver, in order to prevent the discharge of static electricity into the card.

Poka Yoke - Mistake Proofing

A manager started realizing an increasing trend in the breakdown of quality of the results that the electronic equipment was putting out. The voltages that were being produced were going out of specification much more frequently than before, and the manager decided to investigate.

She found that the erroneous output was a function of a card that is installed by a workstation on the other side of the line from where the covers are installed. At first, it appeared that there was a severe manufacturing defect in the cards and the workstation that was producing the card. The manager decided to take a closer look, or a “deep dive” and find out through a “fishbone diagram” and root cause analysis what all of the possible causes of a faulty card could have been. After this was done, she realized that there was a possibility the cover was not being installed properly.

It was this time that she monitored the worker installing the covers. 1 out of every 5 times, the worker used a screwdriver that was not properly grounded. This is shown in Figure (1) in the “before” section, where the worker becomes confused with which tool to use. Her immediate reaction was that this worker was being careless, or was not properly trained in the process that he was conducting. Because she was a good manager, she asked the worker why he didn’t use the properly grounded screwdriver. The worker had explained to her that he thought he was using the correct screwdriver, since the both the grounded screwdriver and ungrounded one were on a lanyard and looked exactly the same in every other respect.

Employing Poka-yoke, the manager shortened the lanyard for the ungrounded screwdriver such that it could not be brought to the workstation that installed the cover on the equipment without cutting the lanyard, as can be seen in the “after” section of Figure (1). By doing this, she made it virtually impossible to use an ungrounded screwdriver to install the cover in question, and in doing so dramatically increased the quality of the product.

As stated before, Poka-yoke is not just for managers and business executives. If instilled properly, every worker and employee of the company should be properly trained in the best methods of mistake proofing, and should provide input on how to eliminate the factor of human error.

Mistake proofing is the most effective, and usually the most cost effective, way of increasing quality. The human element is always a variable in every quality equation, but with Poka-yoke, the impact of that variable can be reduced to a mere fraction of a percent of occurrences than if it were never employed.

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Start Cleaning House with 5S – A simple yet powerful lean tool

There are many parts to lean manufacturing. When you, or any of your colleagues, start thinking about lean, you probably begin with the aspect of paperwork reduction. Of course, we all feel the pain of excessive and tedious red tape, but lean processes, in fact, touch on every single part of manufacturing, and non-manufacturing, business practices.

5S is a perfect example of a bottoms-up approach to the lean methodology. There are many businesses, particularly in manufacturing, that are incredibly disorganized, leading to massively inefficient business practices, lost time, and sometimes even workplace injuries. 5S refers to the practice of workplace organization, and the methodical process of optimizing the layout of a manufacturing plant or workstation to become the most efficient, upbeat, and productive workplace it can become.

Appropriately named, 5S is the name given to the process because each step starts with the letter ‘S’. Started by Toyota in the 1960’s, it has framed the success of many manufacturing plants. The fundamental basis behind 5S is that a person or workstation will never waste time looking for tools and equipment because everything has its own place, is appropriately labeled, and flows to the point where the tool is within reach of where the worker will find themselves when working. If 5S is implemented properly, it is common to see efficiencies increase by a solid 20-30%.

One of the more common missteps when a company implements 5S is to have the focus come from the top-down, with management recognizing the need for process improvement, but never consulting with the worker that will be practicing and implementing the 5S on a daily basis. Without buy-in from every person on the shop floor, a company will never truly achieve the goals outlined by a 5S method.

The 5 S’s, while seemingly complex, are actually relatively straightforward and simple. They are best viewed as pieces and independent of each other instead Concept of 5S simplifiedof holistically. If broken down into its fundamental parts, the 5 steps, you will find that they are nothing more than a standardized approach to optimization. As you can see in the Figure (1), the 5S concept is one in which every step should be intertwined within each other. If an organization is truly on board with the 5S process, the sustainment of the process should maintain a constant cycle of improvement, and each ‘S’ should merge with the other steps, making it near impossible to determine when one starts and the other begins.

The first ‘S’ is “Sort”, or “Seiri”. Management, or possibly the workers themselves, should go about the workplace and take note of which tools, equipment, and supplies are not needed for the everyday operation of the plant. If one is not needed, it is discarded, or at the very least, removed from the shop floor. Some tools and equipment will not be able to be discarded or removed because they are used, but only infrequently. If this is the case, then these tools should be noted as infrequently used, to be dealt with later.

The next phase is oftentimes considered the most important phase of the five. This is where items are arranged, or ‘Straightened‘ (or ‘Seiton‘) systematically and methodically. All of the tools that were identified as unnecessary in the ‘Sort’, phase have been discarded, so this phase should be easy. You just simply place the tools such that workflow is maximized, and no tool is any more than 30 seconds away from even the least experienced worker. This step is best accomplished either by the worker that will be conducting the work or with their direct input.

It may help to include a diagram of all tools and their locations that is readily accessible for reference for the worker during this step.

The next, and least popular stage is ‘Sweep’, or Seisō. This step is where the shop is cleaned, and a new policy of periodic cleaning is implemented. Most manufacturing facilities find that performing this step at the end of every shift is the ideal time for this action. The most important aspect here is to maintain the shop in the order in which step 2 has identified as being ideal.

As discussed earlier, all of the processes described here are not worth anything unless complete buy-in by the average worker on the floor is achieved and practiced. This is where step 4 comes in, ‘Standardize’, or ‘Seiketsu’. This is the step in which all personnel who will be practicing the 5 steps on a daily basis are brought completely onboard and the practices are standardized by forms, procedures, personnel assignments, and workstation ownership.

The final step is that of ‘Sustain’, or ‘Shitsuke’. This step focuses on the requirement to maintain a constant expectation of good lean practices through feedback systems, evaluation and mentoring, training, and auditing. The company has come a long way in improving the workplace, and maintaining it in that improved state is a necessity.

It may not always be apparent as to when a company should use the 5S methodology to improve the workplace. Before any improvement is attempted, management should commission a study to improve their chances of finding the processes that should lead to a leaning of the workplace through 5S. The following is a good example of how the entire process can be conducted.

A new manager was hired to help improve the processes conducted on the shop floor of a generator manufacturing plant. The second day on the job, he notices something that triggered his experienced eye: a worker was walking all the way across the floor, passing by two working cranes, to go to a toolbox and retrieve a specialized tool in order to perform one of the steps he had to perform in order to output a certain component characteristic to his workstation.

The manager requested approval from his management to conduct a 5S study in order to identify places in which improvement could be achieved.

For one full shift, he plotted out the path of the worker he took note of earlier. He found that not only did the worker go to the toolbox while walking under the crane, he also made a couple of stops to the grinding workstation to polish a part, which was on the other side of the shop as well.

The next day, the manager talked in depth to the worker, and helped go through his workstation. He found that there was about 11 tools that were old, outdated, and never used anymore. Thos tools were immediately discarded. After this, the manager helped the worker get a new set of tools that included the one he was going to the toolbox for. He also subtracted the polishing of the part from the process and instead added it to the procedures for the workstation that actually had the grinder at the station. This way, a separate trip was not necessary for the tool nor the grinder.

After they went through and rearranged the tools such that they were always within arm’s reach for the worker, they came up with a schedule for the entire shift to clean the last 15 minutes of their shift. These were all written down and signed by every worker in every shift.

This is a simple example, but most 5S implementations are this simple. If you have any interest in making your manufacturing plant more efficient, you have to start looking at each workstation as a conduit in which work should flow with no restriction. Do this, and your profits will skyrocket.

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Lean Manufacturing Tools Series

It is true to say base of lean manufacturing is its concepts. But lean tools are very important too. They help in implementing, monitoring, and evaluating lean efforts and its results. On the other hand if used without proper understanding this can spoil your lean efforts. So it is very important to understand the tools before thinking about using them.
So I thought of publishing a series of posts on these tools. I got the assistance of an experience contributor in making this series.
Some of the tools we are going to discuss in this series of posts are listed below. I have no doubts you have been waiting for this kind of information.

1. 5S
2. Error proofing (Pokayoke)
3. JIT
4. Kaizen
5. Kanban
6. Pull system
7. Work leveling – Heijunka
8. Work cells
9. Quick Changeover or SMED
10. TAKT Time
11. TOC – Theory of Constraints
12. VSM – Value Stream Mapping
13. Workflow Diagram
14. TPM – Total Productive Maintenance
15. Visual workplace
16. Cause and Effect Diagram
17. 5 Why technique
18. Six Sigma
19. Hoshin Kanri
20. Jidoka
21. Genji Gembutsu
22. Andon

Bookmark this page and visit frequently for updates. If you have any tools want to add to this series please let me know by dropping an email to azabadurdeen@yahoo.com

Always remember, lean should start from its concepts. Tools are only to help you.