J UST - IN -T IME M ANUFACTURING

(Steve Krar, Consultant – Kelmar Associates)

Just-In-Time (JIT) manufacturing is a concept of stockless production that was developed to assist manufacturers who were looking for ways to improve productivity, reduce costs, reduce scrap and rework, overcome the shortage of machines, reduce inventory and work-in process (WIP), and utilize manufacturing space efficiently, Fig. 10-5-1. The JIT process is aimed at organizing manufacturing processes so that the best quality parts, manufactured or purchased, are supplied to the shop floor only when they are needed – not too soon and not too late.

Fig. 10-5-1 JIT strategies eliminate waste through inventory reduction, shorter lead times, product and process design, education, and other related programs. (Kelmar Associates)

JIT originated with the Toyota automobile company; its initial concept was to supply or produce parts only when they were required for the manufacturing or assembly process. Through careful planning, it was found that there was much waste that could be eliminated, plant space better utilized, and overall productivity improved. Its success led to a revolution in production planning and inventory control.

CONVENTIONAL vs. JIT MANUFACTURING

PROCESSES

In a conventional batch-oriented manufacturing operation, parts are bought or produced in mass quantities to take advantage of quantity discounts and machine setups. This strategy seems to be efficient since parts are pushed through a system due to the economics of manufacturing and purchasing. A push system feeds on itself by forcing parts to be produced faster, only to have to wait longer before they are used in the manufacturing process. Parts are generally wanted early because of the unreliability of the parts being available at the time they are required. This leads to large inventories and over reliance on informal manufacturing and inventory control systems. JIT is a pull system in which parts are manufactured only when they are needed, sometimes resulting in machines and workers being idle at times. Parts are bought or produced, then pulled to the next workstation based on when they are required.

No parts are produced until an authorization, commonly called Kanban (Japanese word for authorization), is issued from the next workstation. Once this happens, the workstation is open and parts can be sent to this station to be processed. If the workstation is not ready to receive parts because others are still waiting to be processed, the parts wait at the present locations until they receive authorization. If delay happens often, the process in the specific workstation must be changed to eliminate as much of the delay as possible.

DEFINITION OF JIT

JIT can be defined as the philosophy of business excellence that can be reached through eliminating waste wherever it occurs. Considering only the manufacturing portion of a business, waste can be defined as anything that does not add value to a product. The definition is a little unclear when defining value and product.

The easy and widely used way to explain value is to define it in traditional accounting terms. Value is the actual work done on a product in fabrication, machining, sub- and final assembly that increases the value of a product. Any work or activity that increases the cost of a product without increasing its worth is waste. A product may be any item that is produced during a manufacturing operation.

The problem with this definition is that attention is usually focused on the shop and ignores that JIT principles must also apply to the office. Inventory and set-up time reduction programs, total quality control programs to eliminate the need for inspection, scrap and rework, and equipment layout to reduce travel distance are all shop oriented.

JIT can be seen as a manufacturing revolution that can make a company competitive, free up working capital, improve product quality, while reducing leadtime and manufacturing costs.

There is no better way to showcase a JIT program than to attack some of the highly visible areas of waste on a factory floor. Office applications are not quite as visible, but have an important effect on the success of a JIT program. Companies have always known that waste exists on both the factory floor and in office applications and that eliminating any or all waste would make their operation more efficient and profitable. Taking an overview of JIT itself, it is nothing more than common sense. The key is to identify value-added processes in every area of manufacturing, regardless of traditional accounting definitions that tend to lump certain activities into overhead that do not add value to a product. JIT is not a replacement for shop-floor control, a zero inventory program, a set-up or lead-time reduction program, or a zero-defect program.

All these examples apply JIT principles to problem areas, they are not JIT programs. JIT is not a type of program, it is:

• A goal and philosophy that is aimed at achieving business excellence

• A business-wide strategy whose goal is to eliminate areas and causes of waste through inventory reduction, lead-time reduction, quality assurance, education, product and process design, system design, vendor qualification, and other related programs.

Waste is anything that does not add value, as real worth by the customer, to a product. Worth includes functionality, performance, product quality, design, reliability, availability, aesthetics, warranty, and service.

A product is a manufactured item produced by a shop or industry. The information required to manufacture that product is produced by an office. Information is an important raw material without which a product cannot be designed, built, tested, marketed, and sold.