Lean Manufacturing , GATE & ESE , Industrial Engineering , Mechanical Engineering (New topic added in GATE)

 Lean manufacturing

• It is a set of tools and methods that aim for the continuous elimination of all type of waste from the production system. 
• The main benefits are lower production cost , increased output and shorter lead time.
• Lean production is an approach to identify and eliminate waste and non value added activities through continuous improvement and increasing customer value.
• This lean word comes from the ability to achieve more with less resources through continuous improvement by elimination of waste.
• Lean manufacturing aims at improving system and procedure to deliver more resources and better product with lesser input .
• It consider use of any other purpose than the creation for value of customer as undesirable and to be wasteful and so it should be eliminated.

Five main principles

1. Value: Determine and specifying what adds value to the customer and what does not .Customer needs a good quality at a good price and with fast delivery speed .quality of the product should meet the customer expectation . Non value added process are those which customers are not willing to pay . These non value added processes increases the cost of the product and delay the manufacturing process.
2. Value stream : This involve every step of the process starting from the supplier and ending with the customer. Every step must bring product closer to the  completion and add value to it.
3. Make the product flow: All the obstacles that are constraining the flow of the parts through the manufacturing process must be removed . Lean production strive for one piece flow which is about providing smooth flow for each piece of product with no waste in time , performance and quality in order to deliver the product quickly to the customer.
4. Pull not push : Producing the what the customer need and avoiding over production . Product should be only produced when there is demand from customer side.
5. Achieve perfection:  There must be a vision for perfection , company should try to improve the process rather than being good at what they are doing .

Waste

The seven wastage are those non value added steps or process that reduce the flow of stream, add cost to the product , reduce quality and delay the process.

Central theme of lean

• Muda - waste , NVA (non value added activities )
• Mura - uneven , non uniform , irregular
• Muri - over burden

Muri and Mura leads to Muda (waste)

Example:

30 tones of  iron to be transported 

Trucks - safe loading capacity limit - 15 ton/truck

1. Muda - 3 truck for 10 ton each 

2. Mura - 2 truck , one loaded 20 ton and other for 10 ton

3. Muri - one truck with all 30 ton load

4. No muri , mura and muda - 2 trucks of 15 ton each

Original 7 waste (Muda)

TIMWOOD (to remember the waste names)

1. Transportation 
2. Inventory 
3. Motion 
4. Waiting
5. Over/excess production 
6. Over processing 
7. Defects
8. Unutilised skill or manpower or human 

a) Transportation : main factors for better efficiency

• Layout of plant 
• Distance between different manufacturing process and setup
• Distance between machine inside each work station 
• How close are the work station and machine to the tools
• How far away are the inventory warehouse from the production unit.

b) Inventory: main points for cost effective inventory

• Return on investment 
• Risk should be less
• Material handling 
• Space 
• Insurance and taxes

c) Motion: 

• This is ergonomics , the operator needs to have its tools and parts handed to him in exactly the right orientation to eliminate wasted walking and handling losses.

d) Waiting: This is the time wasted factor and it involve the following activities

• Waiting for material 
• Waiting for spare parts
• Waiting for quality inspection 
• Waiting due to low machine performance and speed

e) Over production: 

• It is related to inventory and simply means that making more product than what is actually needed or over the capacity of sales department . It is a waste of money and time . The method like kanban can be used to make the product according to the customer's demand.

f) Over processing:

• It means making more steps in the process than what are actually needed or using the steps that can be eliminated .

g) Defects:

h) Unutilised skill or man power or human:

Pillars to achieve lean manufacturing

1. Five S

• Sort - remove things that you do not need
• Set in order - arrange essential items in such a way that it is easy to access them .
• Shine - keep working station tool and machine clean and keep them in proper order .
• Standardise - establish rule , checklist , standard and procedure to keep everything clean and in order.
• Sustain - convert 5s into habit , use visual language and sign board to sustain the habit.

2. JIT 

• KANBAN/(MRP+JIT)

3. Kaizen (continuous improvement )

It is a japanese business philosphy regarding continuous improvement of operations and involve all employees.

The main steps are :

• Continuous small improvement
• Changes are implemented quickly
• Everyone gets involved

4. Cellular technology

Manufacturing cells are decide to process parts of the product in seprate fixed area , thus eliminating the non value added activities , production work station and equipment are arranged in a product flow sequence such that the layout create a single piece flow . This layout increase production velocity and flexibility . It increase the order flow time , work in process material handling cost and thus increasing the customer satisfaction.