Last edited 08 Apr 2021

Just in time


[edit] Introduction

Just-in-time (JIT) is a production and delivery system developed in Japan in the 1960s and 1970s that ensures materials and components are delivered from the manufacturer to the production site at exactly the right moment to enable immediate use in the production process.

The right materials are supplied in the right order, in the right amount at the right time. The deliveries tend to be regular and in small amounts. The process is also known as ‘Just-in-time production’ and the ‘Toyota Production System’. In recent years the term has been used synonymously with lean manufacturing.

JIT can be critical for some manufacturing processes (such as cars) as it greatly simplifies logistics: components are delivered directly to the production floor so manufacturers do not have to store or warehouse them (or else they only require minimal storage), thereby saving space, time and costs – and making for a more efficient process overall.

Known as a ‘pull’ process, the JIT concept was developed in Japan and is used by the Toyota car company which uses ‘Kanban’ (sign) boards for ordering parts: when a part has been used, the Kanban is taken off the packaging and sent back to the preceding process as an order for an additional item. This sign-based scheduling system signals the need to replenish the product and delivery and maintains production at an optimum level.

Drawbacks of the system are that it works best when production numbers are constant. Also, it is vital that every part fits as it is intended to first time round as there are no other parts available at that time. In addition, if a problem or minor disruption occurs in the supply chain, the manufacturer has no stocks to fall back on and could see production halt at short notice.

[edit] Just-in-time in construction

Products and materials constitute a huge part of the construction process and it has been estimated that greater efficiencies in logistics can reduce waste in construction by up to 35%. Many projects can benefit from JIT delivery and, given the often congested nature of construction sites, rewards similar to those seen in manufacturing industry may be possible.

A prime example is ready-mixed concrete: the perishable nature of this material means that having been mixed to the customer’s exact specification, it must be delivered at the right time, in the right quantity (and at the right specification) to allow pouring before setting takes place. Another example is windows or glazed cladding panels, where on-site storage would necessitate extensive inventory facilities and potential risks of product damage.

JIT in construction has also been referred to as ‘lean construction’ – an adaptation of lean production techniques.

[edit] Just in time delivery / logistics

The BIM Overlay to the RIBA Outline Plan of Work, published by the RIBA in 2012 defined just in time (JIT) delivery, or just in time logistics as: '..receiving raw materials,
products and parts in the factory and then on site as they are needed, rather than days or even weeks before. This allows businesses to significantly cut inventory costs by having fewer unnecessary supplies on hand, and means they have far less material to store and handle. Where buffer stocks are considered necessary (e.g. as a result of a risk analysis), they are specified in terms of time periods linked to the assembly plan (e.g. one day of manufacturing).'

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