Just In Time

Just In Time "Just In Time" or "JIT" is a philosophy which aims to eliminate waste. Thus it’s about Efficiency It does this through reducing inventory and increasing throughput and quality.

Ohno (1972): "Just-in-time means that, in a flow process, the right parts needed in assembly reach the assembly line at the time they are needed and only in the amount needed. A company establishing this flow throughout can approach zero inventory." The fundamental concept of JIT is that it is good practice to manufacture what the customer requires at the time it is required rather than to tie up working capital and space in finished goods inventory.

What happens if you make items in very small batches? Var Vol Var Vol

JIT and batch sizes Sandras (1987) claims that the way to move towards Just in time is to learn how to economically manufacture "one less each time". As constraints are exposed these should be tackled. See the Lake and Rocks analogy.

Lake and Rocks

JIT and Waste "Waste" is any activity that does not add value for the customer. Waste can be excess inventory, setup times, inspection, material movement, transactions or defects. Any process that does not actively add value is waste and should be minimised and eliminated.

The Seven Wastes (Shingo 1985): Waste of over production Over production or production of items too early, which causes unnecessary inventory Waste of waiting This refers to operators. Operators should always be occupied doing something useful Waste of transportation Poorly designed layout causes unnecessary transportation. This adds no extra value to the product and is wasteful Waste of stocks Stock itself is wasteful because it ties up capital and also because it needs to be transported, stored and found when needed

Seven Wastes Waste of worker motion Unnecessary fetching and carrying of materials or components adds no value, therefore it is waste Waste of making defects Defects cause scrap, rework and damage to related parts. None of these adds value and therefore they are waste. Waste of processing (when the process should not be used). This refers to using a machine which is more than capable of doing the job. The opportunity of using the machine for something for which it adds more value may have been wasted. Waste of operation It is wasteful to use poor methods which can cause quality problems, damage to parts at later stages and unnecessary rework.

JIT and productivity Taiichi Ohno (1978): JIT is about making more with the same or fewer resources. If a production line of ten men improves production by 25% then the original volume can now be produced by 8 men. Ohno would suggest that the extra two people can be used in other ways, and if not then they should be made redundant.

Quality and JIT Crosby (1979) defines quality as "conformance to customer requirements" Deming (1982): "meeting or exceeding the customers requirements" ( Wasteful?) Companies attempting to use JIT techniques are removing the comfortable slack (safety stock and safety lead time) which allows production to continue on most work centres most of the time, despite quality problems. The Just In Time philosophy helps to overcome quality problems, line imbalances and machine breakdowns. Sandras: "JIT and TQM are two sides of the same coin"

Does JIT agree with the Goal? Why is Inventory so important in Japan?

Just In Time Procurement Ohno (1978): Toyota have deliveries to their plants in Japan several times per day of batches which allow only a few hours production. (Now not uncommon in other countries) - reduced inventory, obsolescence - increased flexibility - less space required ? more ordering ? more traffic through receiving dock

Toyota (etc) can insist on these arrangements, due to high volumes purchased. Local Products Ltd probably can’t. Higher variety, lower volume companies can reduce number of suppliers and move to JIT deliveries for high value-of-use items

Just In Time shopfloor control JIT - philosophy of eliminating waste Kanban - control system used at Toyota Kanban is the Japanese word for card, sign (shop sign) or signal. In this context it means the cards that regulate production. Cards are used to request material, which is only produced when requested. WIP is proportional to the number of cards. Reducing the number of cards reduces inventory and exposes problems.

Types of Kanban Single Card Kanban Dual Card Kanban

Single Card Kanban

Dual Card Kanban

Can Kanban make us into a Toyota? Many authors, including Ohno and Browne et al, suggest that the kanban card system is over-emphasised in the literature on JIT, at the expense of the JIT philosophy and JIT manufacturing techniques. Browne et al: "In particular, we feel that JIT can be applied to good effect in all types of discrete parts manufacturing systems while kanban can only be used in repetitive manufacture". Ohno believes: "The success of Toyota is 1/10 due to kanban and 9/10 due to other factors in the Toyota Production System".

Arguments against JIT High costs of multiple JIT deliveries Quality problems

High costs of multiple JIT deliveries “call off" system: schedules of requirements given to a supplier for up to a year in advance eg 200 over the year, delivery weekly Supplier delivers the number called for each week, which will be allowed to vary. single order to raise smoother demand for supplier regular payments suit both parties reduces inventory may help develop long term partnership

Quality problems Without safety stock and safety lead time, quality problems can no longer be hidden Implementation of TQM in the company and in critical supplier companies. Deal with problems instead of avoiding them

Reading JIT and Kanban have been well covered by Ohno, Shingo, Schonberger, Sandras, Bicheno, Parnaby, Burbidge, etc