Lean Manufacturing


The popular definition of lean is: “It is a comprehensive set of techniques that, when combined and matured, will allow you to reduce and then eliminate the seven wastes. This system not only will make your company leaner, but subsequently more leaner more flexible and responsive by reducing waste.”

“A systematic approach of identifying and eliminating waste (non-value-added activities) through continuous improvement by flowing the product at the pull of the customer in pursuit of perfection.” 

The process is called lean because finally it runs on:

  • Usage of lesser material
  • Less investment
  • Less inventory usage
  • Consumption of less space
  • Using less manpower
  • Reduction of chaos
  • Emotionally leaner

LEAN AND TOYOTA PRODUCTION SYSTEM (TPS)

To understand lean better TPS works as a model. It is one of the best lean systems around. It is also the best documented system around and has stood the test of time. The three key statements which define Ohno’s TPS are

  •  “The basis of Toyota Production System is the absolute elimination of waste.”
  • “Cost reduction is the goal”
  • “After World War II, our main concern was how to produce high quality goods. After 1955, however the question became how to make the exact quantity needed.”

It is not the brilliance innovations in products, culture, or weak currency that helps this company to stand out from among all the other companies at the global level. It is the brilliant focus on the core processes.
PRINCIPLES OF LEAN

Lean is based on five principles. These are:

  • Specification of product/service value
  • Value stream identification and waste removal
  • Uninterrupted product/service flow
  • Focus on pull by customers i.e. pull production
  • Work towards perfection and continuous improvement

Value adding to a product: Any process done during production that a customer is willing to pay for Non value adding activities: Activities that absorb resources without adding any beneficial value to the product.

CHALLENGES TODAY

The paradigm of manufacturing is shifting with the emergence of new trends.

  • Competition Global: With the MFA getting abolished, free trade across countries results in tough completion. Usage of lean helps in achieving low cost production.
  • Customers Looking for quality at low cost: Today the customer believes in value for money. There is a wide variety of products available within the same price quote. Lean here helps in reducing production time without compromising on quality.
  • Fast fashion: With the emergence of fast fashion it is vital to prevent inventory overload which can be achieved with the usage of lean. Change With the decreased product life cycle of products, production needs to be quick and flexible. Achieving this is the main objective of lean production.

OBJECTIVES OF LEAN MANUFACTURING

Minimise defects and wastages: reduction of defects and unnecessary physical wastage, including any excess input, defects that are preventable, added costs associate with reprocessing goods.

  • Reduce cycle times: reduction of lead time and production cycle time during different levels of production.
  • Inventory levels: minimise inventory levels at production stages, particularly work in between production stages. Low inventory means lower working capital requirements.
  • Labour productivity: improvement through reduction in idle time and ensuring work efficiency during the working time of the workers.
  • Utilisation of equipment and space: eliminating bottlenecks and maximising production rate by minimising machine downtime.
  • Flexibility: to have ability to produce more ranged products with minimum changeover costs and time.
  • Output: improving output through reducing cycle time increased labour productivity etc.

THE SEVEN BASIC WASTES

Waste is anything lying in the inventory without serving any kind of purpose. The goal is on the overall system and syncing operations so that the pace is kept steady and the products are produced at a uniform pace.

  • Over production: any product that cannot be sold or has to be dumped at a lower price is wasteful. Producing products before the customer needs it requires the product to be stored and ties money in the inventory.
  • Inventory: excess inventory ties cash which is wasteful
  • Conveyance: unnecessary moving parts during production are damaging as well as wasteful.
  • Correction: having to rework parts due to manufacturing errors wastes resources. Additionally sorting and inspection is difficult and can be eliminated using error proofing.
  • Motion: improvement in equipments that put undue stress on body and cause waste.
  • Processing: unclear customer requirements cause addition of extra processes, which add to the cost.
  • Waiting: operator being idle between operations is wasteful. It is not acceptable if the operator waits on the machine.

LEAN TOOLS AND TECHNIQUES FOR WASTE REMOVAL

  • Kanban: is an information system used to ascertain that production occurs only when demand is created downstream. It adopts the pull system and is categorised into three types:
  • Total productive maintenance: “The combination of best features between productive and predictive maintenance with total employee involvement.
  • Withdrawal kanban: used by the subsequent process to request and remove in process inventory from the preceding process.
  • Production kanban: a go ahead for preceding process to cater to the demand created subsequently.
  • Supplier kanban: circulates between supplier and manufacturer.
  • Just in Time: eliminates waste by producing the right part for the right place at the right time. It enables internal process of a company to adapt to changes in demand by right production at the right time. It helps in reducing average error in the production.
  • Kaizen: means continuous improvement. The approach is a gradual, orderly, continuous improvement. In manufacturing improvement takes place in reduction of inventory and defective parts. It uses a tool known as 5S which is:
  • Sort: moving and tossing needless items
  • Straighten: work place tools must be marked and arranged as belonging to their area.
  • Shine: maintain cleanliness.
  • Storage: maintain storage units dexterously.
  • Systemise: maintain high standard housekeeping and work arrangement. Standardised work: it describes each work activity by specifying time needed to finish the job. One of the tools that help standardise work is Takt time, which is the time between units of production output in synch with customer demand. Takt time=available work time per day/customer demand per day.
  • SMED: Single minute exchange or die is used to very quickly change machine/processes over from producing a specific part number or product orchanging attributes of the part number or product. The processes are highly choreographed and rehearsed to minimise machine downtime.
  • Value stream mapping: integrates material and information flow to understand the relationship between all the value added and non value added activities and their importance. It includes both the value adding activities as well as non value adding activities.
  • Production smoothing: using this, the manufacturers try to keep the production level as constant as possible from day to day. This is adopted from TPS where the products are made according to the requirement.

DISADVANTAGES OF LEAN

  • Investment costs: the potential and attitude to invest in a performance enhancing activity like lean manufacturing is still a big question. It still has a long way to go
  • Lack of understanding of lean principles: many industrialists fail to understand the lean concepts and their impact on manufacturing.
  • Lack of communication: lean needs sound communication at all the hierarchy levels to function with ease. Every employee is not given the same importance in many other companies.
  • Inabilities to quantify the benefits: many domestic producers are at a disadvantage due to their inability to comprehend and quantify the benefits of lean production techniques.

TRADITIONAL PRODUCTION VS LEAN MANUFACTURING

JOB DEFINITIONSPECIFICATION SPECIALISATION STANDARDISATIONMUlTITASKING MULTIFUNCTIONAL TEAMWORK
QUALITY CONTROLSEPARATE FUNCTION IN THE PROCESS OF EACH JOB DESCRIPTIONALL WORKERS ARE DEEMED RESPONSIBLE FOR QUALITY CONTROL
PRODUCTION PROCESSINFLEXIBLE LARGE SIZEFLEXIBLE AND QUICK CHANGEOVER
INVENTORYLARGE BUFFER STOCKLEAN
COMPETING ONPRICE, ECONOMIES OF SALEQUALITY, FLEXIBILITY AND PRICE ECONOMY
COST REDUCTIONDRIVEN BY VOLUME AND PRICEDRIVEN BY VALUE ENGINEERING
PRODUCT FLOWSINGLEMIXED
LEADERSHIP AT DIFFERENT LEVELS,COORDINATORS WITH LIMITED AUTHORITYA PROJECT LEADER WITH FULL AUTHORITY
OUTCOMESLOW QUALITY LOW COST PRODUCTIONLOW COST HIGH QUALITY PRODUCTIONL PRODUCTION

 

An article by:-

Shubhi Dwivedi

National Institute Of Fashion Technology, Bengaluru