Lean Manufacturing: SMED and JIT production

Companies are always searching for ways to reduce waste in the manufacturing process. Lean Manufacturing is one of the most common strategies used to reduce waste and improve the overall process. Single Minute Exchange of Die (SMED) and Just in Time (JIT) production are two methods used in lean production to help reduce waste.

Exchange of Die (SMED)

SMED provides a rapid and efficient way to covert a manufacturing process from running a current product to running the next product in line. The rapid changeover to a new product is part of the lean principle, Mura. Mura is aimed at improving the overall flow of production.

The concept behind SMED arose in the 1950s when Shigeo Shingo, of Toyota, was looking to find a solution to their bottlenecking problems in the car body-molding process. Long change-over times were causing the bottlenecks to occur and were increasing the overall production lot size. If a change-over takes too much time it increases the overall cost of the actual production. Due to high land costs in Japan, Toyota found it difficult to store economic lots of their vehicles. The economic lot size (EQQ) for Toyota cost more than their competitors and Shingo could not find a reasonable solution. SMED was created to reduce costs by implementing smaller lot sizes. Toyota reworked vehicle components to minimize the assembly tools and extra steps in the manufacturing process, thereby reducing change-over times.

Shigeo Shingo created 8 techniques that need to be used if you are implementing SMED:

1. Separate your internal and external operations
2. Convert internal steps to external setup
3. Standardize function instead of shape
4. Use functional clamps and eliminate fasteners altogether
5. Use intermediate jigs
6. Adopt parallel operations
7. Eliminate adjustments
8. Mechanization

There are 4 conceptual stages that also needed to be followed as you implement SMED. First, you must ensure that the external setup applications are performed as the machine is in process. Second, All the internal and external actions need to be separated to ensure that the parts function properly and are efficient in transporting the die and other necessary parts. Third, you must convert internal setup actions to be external ones. Fourth, the final stage is to improve all the setup actions.

SMED is completely focused on reducing changeover.

Using the 7 basic steps below, you will begin reducing changeover:

1. Step one is to observe your current methodology and evaluate it.
2. Step two is again to separate the internal and external activities. Your internal activities consist of anything that can be performed when a process is stopped. Your external activities consist of anything that can be done when the process is running.
3. Step three is to convert internal activities to external ones if it is possible.
4. Step four is to streamline all the remaining internal activities to be a simplified process.
5. Step five focuses on streamlining all the remaining external activities to be like the internal ones.
6. Step six is to document the new procedures.
7. Step seven is the final step and that is to repeat steps 1-6 until you see an improvement.

When you begin implementing SMED, you can use additional toolkits to help the process. Some popular toolkits include: visual control, checklists, attachment plates, 5 S Methodology, overhang tools, locating pins, stopper, and other tools.

Remember that SMED is focused on 3 things: internal setup, external setup, and identifying and eliminating wasted motions and non-value-adding activities.

Just in Time (JIT) Production

Just in Time Production (JIT) was first used by the Ford Motor Company in the early 1920s as an inventory strategy to reduce inventory. When Toyota began work on the Toyota Production System, they look at some of the methodologies that were implemented by Ford. They found that Ford had a part of JIT production, but they did not fully implement the entire strategy. Toyota discovered that Ford had piles of excess inventory lying around their facility and their employees had uneven work schedules. Toyota also visited Piggly Wiggly and saw a fully functional JIT production program in work.

JIT production is considered an inventory strategy that is implemented to improve the return on investment (ROI) of a company by reducing the in-process inventory and its associated costs. JIT must have different signals about the process and identify what is happening within the process. Because JIT is driven by signals, it falls in line with the Kamban methodology.

The Kamban system typically uses visual signals or tickets to indicate a missing item or designate where a particular inventory item is stored. JIT can lead to significant improvements in your quality, efficiency and ROI. The JIT inventory reduction can be the consumption of old stock which triggers new stock to be ordered. By reducing JIT, you are saving on warehouse space and costs. Typically stock levels are determined by historical demand and when a sudden demand rises above the average, your inventory will quickly diminish faster than usual and may cause customer service issues. By using the Kamban system, you will be able to flex your inventory system so these issues won't occur.

There are several components you can use when you implement JIT. Again, there is the Kamban system, production leveling, pull systems, Total Quality Control, and several others. So many people have used the Kamban system with JIT, that the two have become synonymous with each other. To implement the Kambam, you will attach a kambam to each box of parts as it moves along the assembly line. The worker in the process will collect parts from the previous process, leaving a kambam that states the delivery of a certain amount of product. All the parts are then funneled to the line and used as they are needed and the same kambam is returned back to the area to serve as a record of the work done and to implement an order for new parts. The kambam coordinates the overall inflow of parts and components to the assembly line and minimize the process.

The benefits for using the JIT systems include:

• Reduced set up times in the factory. By cutting down the set up time, your company will be more productive and will be able to improve their bottom line. This will allow your company to look more efficient and you can focus time on other areas in your production line that need improvement. During this phase you will be using SMED to reduce the overall changeover time.
• The flow of goods is improved. By having your employees focus on specific areas in the overall system, they will be able to process goods faster because they won't be fatigued from doing too many jobs at one time.
• Employees are utilized more efficiently. When employees are trained to have multiple skills, they can be utilized more effectively. By having your employees trained to work on different parts of the inventory cycle, you will be able to use workers in areas when they are needed or when there is a shortage of workers on a product in high demand.
• Consistent scheduling and employee work hours. A simple method to implement is if there is not a demand for a product at a given time, the employees don't need to be working. This will save your company a lot of money because you won't need to pay workers for a job not completed.
• Better supplier relationships. Because you will have more time, you will be able to work harder on establishing your supplier relationships. Having a trusted supplier will give you the peace of mint to know when you can rely on goods to be delivered, how they will be delivered, and if they are satisfactory to your consumers.
• Workers are more productive because the supplies are evenly distributed. Since management is now focused on meeting deadlines, the employees will work harder to meet the deadlines and a continuous stream of supplies can help them stay busy. The employees will see the benefits of their work through job satisfaction, promotion, or pay increases. One major problem with JIT production is the large supply and demand changes. While it is nice to maintain a consistent inventory level, your consumers could face a supply shock. You will need to use production leveling to help remove the slight variations that come with inventory holdups. Toyota has recognized this problem and they have decided to only use 2 suppliers for most of their assemblies. By using the same 2 suppliers, Toyota is reducing their chance at having an interruption in the production flow. Toyota has also established a long-term relationship with their suppliers and are thereby given short-term, low pricing as compared to pricing from competing suppliers. JIT is a proven methodology and will help you build relationships with your suppliers. By having excellent suppliers, your margin of error will be improved because you know the exact quality of the product you will be receiving and you trust who is giving you the product.