Just-in-time (JIT) is defined in the APICS dictionary as “a philosophy of manufacturing based on planned elimination of all waste and on continuous improvement of productivity”. Just-In-Time (JIT) production system was founded by Taiichi Ohno (a Vice President at Toyota) and first successfully implemented at the Toyota Motor Company’s plants in Japan. Just-in-time production, or JIT, and cellular manufacturing are closely related, as a cellular production layout is typically a prerequisite for achieving just-in-time production.
JIT (also known as lean production or stockless production) should improve profits and return on investment by reducing inventory levels (increasing the inventory turnover rate), reducing variability, improving product quality, reducing production and delivery lead times, and reducing other costs (such as those associated with machine setup and equipment breakdown).see fig (a) JIT applies primarily to repetitive manufacturing processes in which the same products and components are produced over and over again. The basic elements of JIT were developed by Toyota in the 1950s, and became well-known as the Toyota Production System (TPS). JIT was well-established in many Japanese factories by the early 1970s.
JIT began to be adopted in the U.S. in the 1980s (General Electric was an early adopter), and the JIT/lean concepts are now widely accepted and used. The competiveness of Japanese manufactured products has focused attention on their manufacturing systems since the basis of their success has been high- quality, competitively priced products. Some companies, IBM for example, refer to JIT as ‘continuous flow manufacture’; some others ,like Hewlett-Packard, for example, call it stockless production and repetitive manufacturing system; GE calls it management by sight and Japanese firms use the term Toyota System instead of JIT.
Stabilize and level the MPS with uniform plant loading Reduce or eliminate setup times Reduce lot sizes Reduce lead times Preventive maintenance Flexible work force
Require supplier quality assurance and implement a zero defects quality program. Small-lot (single unit) conveyance. J-I-T is a combination of single-unit production and the conveyor system and is called ‘Ikko Nagare’ in Japanese meaning Single Unit Production and Conveyance. It is obvious that J-I-T can be more easily used for continuous mass production of a variety of finished products. It may not be that easy to apply it to the totally customized intermittent production. Effects of JIT See fig (b)
A kanban or “pull” production control system uses simple, visual signals to control the movement of materials between work centers as well as the production of new materials to replenish those sent downstream to the next work center. A kanban is a card that is attached to a storage and transport container. It identifies the part number and container capacity, along with other information, and is used to provide an easily understood, visual signal that a specific activity is required. A J-I-T production system uses a peculiar material withdrawal and work ordering system. This is called the Kanban (or market) system.
The J-I-T system works based on the requirement at the final product level. Basically, it believes in producing at a time only that many items as have been withdrawn. This chain of withdrawal-and-production is continuous from the end product to the beginning process. This is the way the work-in-process inventory is kept very very low. The withdrawal of material from the preceding process and the production of items to replace this are ordered through a withdrawal and production Kanban (or maker card.)
It is physical control system, and is visual in nature which is an advantage over the conventional production control paper work which could be quite confusing at times. The containers for the material are of fixed size, and the production lot-size is that which a container can contain. The number of containers used depends upon: (i) the cycle time for a container to go the next work centre and return, (ii) The rate at which the material is getting consumed, and (iii) size of the container. Needless to say, the number of containers (i.e., the work-in-process inventory) should be small. This can be achieved by reducing the cycle time. This means a reduction in the set-up and conveyance times. (see fig c)
In Toyota’s dual-card Kanban system, there are two main types of Kanban:1. Production Kanban: signals the need to produce more parts2. Withdrawal Kanban (also called a "move" or a "conveyance” kanban): signals the need to withdraw parts from one work center and deliver them to the next work center. Dual-card Kanban Rules:1. No parts are made unless there is a production kanban to authorize production. If no production kanban are in the “in box” at a work center, the process remains idle, and workers perform other assigned activities. This rule enforces the “pull” nature of the process control.2. There is exactly one kanban per container.3. Containers for each specific part are standardized, and they are always filled with the same (ideally, small) quantity.
Short set up times:1. In the Toyota Motor Company in Japan there have been continuous efforts to reduce the set-up times.2. For example, the set-up time of the pressing department which was 2-3 hours during 1945-64 was reduced to 3 minutes after 1965.3. Such set-ups which have single digit (in minutes) set-up times are called single set-ups. Through the use of Quality Circles, set-up times of even less than a minute have been achieved in some cases at the Toyota Motor Company, Japan.4. These may be appropriately called One Touch Set-ups.5. This kind of reduction in set-ups times has been achieved by (i) recognized the internal portion of the set-up being different from the external portion, i.e. activities that can be done while the machine is running,(ii) by converting internal set-up to external set-up as much as possible , and (iii) by eliminating the ‘adjustment’ aspects in the set-up.
1 A simple and understandable process. 2 Provides quick and precise information. 3 Low costs associated with the transfer of information. 4 Provides quick response to changes. 5 Limit of over-capacity in processes. 6 Avoids overproduction. 7 Is minimizing waste. 8 Control can be maintained. 9 Delegates responsibility to line workers.
Data craft Solutions uses the on-demand delivery model because many of the Kanban solutions used by Fortune 100 and 500 companies are well outside the budget of small to mid-sized companies. Datacraft Solutions provides solutions that allow even the smallest companies to remain competitive, without having to incur costly IT expenses. Sharing knowledge is also a key new distinction in the Digital Kanban world; as the solutions continue to spread throughout the manufacturing industry, Datacraft Solutions draws upon the insights and experiences of their client base to enhance the functionality of their product offerings. Data craft Solutions is applying the lessons of continuous improvement to their platform, making the Digital Kanban ( cont..)
Contd.. implementation more efficient and effective as time goes on. This optimization occurs on an ongoing basis. There is no need to reload software and retool hardware; new capabilities are added, ready for manufacturers and suppliers to use the next log in. According to Founder Matthew Marotta, "Datacraft Solutions Internet-based on-demand delivery platform offers key benefits from the very beginning of an implementation namely, the elimination of lengthy, complicated and expensive infrastructure upgrades before you can even begin to see positive ROI. There is simply no faster or easier way to begin exploiting the power of Digital Kanban in your operations."
The term Poka Yoke was coined in Japan during the 1960s by Shigeo Shingo, an industrial engineer at Toyota. Poka Yoke is Japanese for mistake-proofing: yokeru is "to avoid", while poka means "inadvertent errors". Anyone, from regional sales manager to sales associate to document specialist can develop a poka yoke. Poka Yoke devices thus enable avoiding inadvertent errors through behaviour-shaping constraints. People cannot function like machines, with the same result every time. A small distraction can lead to work going wrong. It is not necessarily the workers fault, as poorly-designed processes that require a great deal of attention can contribute severely to problems.
The basic principles of Poka Yoke, therefore, advocate designing or developing tools, techniques and processes such that it is impossible or very difficult for people to make mistakes. Poka Yoke is based on the premise that everyone must work together to achieve zero defects. Poka Yoke doesnt violate or negate good engineering practices. Instead, it expands on those practices to include ways to help people and machines do the job right as well as quickly. First, you need to educate your workforce on the concept of poka yoke (call it mistake proofing for ease). Second, you need to empower your employees to make a bunch of small improvements to their processes -- continuously. What you will end up with a business that wastes less energy, time and resources doing things wrong in the future.
Not long ago Larry Ficarra, and engineer with Varian Ion Implant Systems, Glouster, Mass.., was assembling a vacuum chamber for a 10,000-component particle accelerator used in microprocessor production. A guide pin near an O-ring surface on one component face was supposed to go into a hole on the mating face to ensure proper alignment of critical components. The part with the pin was so bulky it required a little juggling before the pin found the hole. Everything seemed to be working well, but on start up, the critical assembly would not hold a vacuum.
After a lengthy diagnosis, Ficarra discovered that while trying to get the pin into the hole, he had inadvertently scratched the O-ring surface which prevented the chamber from holding a vacuum. During his R&D sessions he discovered the Japanese refer to mistakeproofing as poka-yoke and think of it as their first defense against defects. Ficarra’s poka-yoke solution to the vacuum chamber involved installing alignment pins into components with O-ring sealing surfaces. This prevents the stainless-steel alignment pin from scratching the 16-rms aluminium finish during assembly. The pin may contact the elastomer O-ring, but the complaint O-ring resists damage. Additional pins prevent damage to the sealing surface while a component rests on a bench during assembly or service. Ficarra says the scratched –surface error has not happened since.
A push-pull-system in business describes the move of a product or information between two subjects. On markets the consumers usually "pulls" the goods or information they demand for their needs, while the offerers or suppliers "pushes" them toward the consumers. In logistic chains or supply chains the stages are operating normally both in push- and pull-manner. The interface between push-based stages and pull- based stages are called push-pull boundary or decoupling point.
Push Systems: schedule Pull Systems: authorize work work releases based on releases based on demand. system status. inherently due-date inherently rate driven driven control release rate, control WIP level, observe WIP level observe throughout
PUSH PULL(Exogenous) Schedule (Endogenous) Status Production Process Production Process Job JobPush systems are inherently Pull systems are inherentlymake-to-order. make-to-stock.
If WIP is capped, then disruptions in the line (e.g. machine failures, shutdowns due to quality problems, slowdowns due to product mix changes) do not cause WIP to grow beyond a predetermined level In a pure push system, no such limit exists In a pull system, releases are choked off before the system has become overloaded. A WIP cap regardless of the type of pull system will reduce the average WIP level required to achieve a given level of throughout.
Low Unit Cost: Good Customer low inventory Service: short cycle times reduced space steady, predictable little rework output stream High External Flexibility: Quality: avoids committing high internal quality jobs too early pressure for good encourages quality floating capacity promotion of good quality (e.g., defect detection)
Example – IBM Panel PlantOriginal LineTreater Prepreg, Copper Lamination Machining Circuitize Drilling Copper Plate Push/Pull Interface Sizing, Procoat Test process that givesRevised Line boards “personality”Treater Prepreg, Core Lamination Machining Circuitize Copper Blanks Push/Pull Interface Sizing, Copper Drilling Procoat Test Plate Notes: • Moving push/pull interface closer to customer shortens lead time seen by customer. • Small number of core blanks presents opportunity to make them to stock.
Single Minute Exchange of Die (SMED) is one of the many lean production methods for reducing waste in a manufacturing process. It provides a rapid and efficient way of converting a manufacturing process from running the current product to running the next product. This rapid changeover is key to reducing production lot sizes and thereby improving flow ([Mura (Japanese term)| The phrase "single minute" does not mean that all changeovers and startups should take only one minute, but that they should take less than 10 minutes (in other words, "single digit minute").
Stockless production which drives capital turnover rates, Elimination of unusable stock from model changeovers and demand estimate errors Goods are not lost through deterioration Ability to mix production gives flexibility and further inventory reductions as well as opening the door to revolutionized production methods (large orders ≠ large production lot sizes) New attitudes on controllability of work process amongst staff
Reduction in footprint of processes with reduced inventory freeing floor space Productivity increases or reduced production time Increased machine work rates from reduced setup times even if number of changeovers increases Elimination of setup errors and elimination of trial runs reduces defect rates Improved quality from fully regulated operating conditions in advance Increased safety from simpler setups Simplified housekeeping from fewer tools and better organisation Lower expense of setups Operator preferred since easier to achieve Lower skill requirements since changes are now designed into the process rather than a matter of skilled judgment.
Separate internal from external setup operations Convert internal to external setup Standardize function, not shape Use functional clamps or eliminate fasteners altogether Use intermediate jigs Adopt parallel operations Eliminate adjustments Mechanization
Autonomation describes a feature of machine design to effect the principle of jidoka used in the Toyota Production System (TPS) and Lean manufacturing. It may be described as "intelligent automation" or "automation with a human touch.” This type of automation implements some supervisory functions rather than production functions. At Toyota this usually means that if an abnormal situation arises the machine stops and the worker will stop the production line.
Autonomation prevents the production of defective products, eliminates overproduction and focuses attention on understanding the problem and ensuring that it never recurs. It is a quality control process that applies the following four principles: Detect the abnormality. Stop. Fix or correct the immediate condition. Investigate the root cause and install a countermeasure.
Taiichi Ohno and Sakichi Toyoda, originators of the TPS and practices in the manufacturing of textiles, machinery and automobiles considered JIT & Autonomation the pillars upon which TPS is built. Jeffrey Liker and David Meier indicate that Jidoka or "the decision to stop and fix problems as they occur rather than pushing them down the line to be resolved later" is a large part of the difference between the effectiveness of Toyota and other companies who have tried to adopt Lean Manufacturing. For "just-in-time" (JIT) systems, it is absolutely vital to produce with zero defects, or else these defects can disrupt the production process - or the orderly flow of work.
Autonomation, therefore can be said to be a key element in successful Lean Manufacturing implementations. JIT and Lean Manufacturing are always searching for targets for continuous improvement in its quest for quality improvements, finding and eliminating the causes of problems so they do not continually crop up. Jidoka involves the automatic detection of errors or defects during production. When a defect is detected the halting of the production forces immediate attention to the problem. The halting causes slowed production but it is believed that this helps to detect a problem earlier and avoids the spread of bad practices.