Six Sigma

Lean manufacturing waste:

Lean techniques application is typically focused on seven types of wastes in a production or service system, those wastes at the root of the majority of Following are the seven main types of process waste in lean manufacturing:

1)      Overproduction:producing more than the quantity that is required and/or producing items before they are actually needed. This waste is related primarily to make-to-stock mentality and weak demand forecast.

2)      Transportation:excessive movement of parts or material from or to storage or within the production line. Actually, all forms of material handling are often considered to be non-value-added tasks.

3)      Motion:movements performed by workers or machines before, during or after processing. This often refers to micro-level wastes in work procedures that directly affect cycle time and effectiveness.

4)      Waiting:parts delay in queues that are waiting processing or idle time of operators or machines. In a similar manner, delay occurs when holding inventory for production or making customers wait for services.

5)      Processing:non-value-added processing and use of materials, tools, and equipment. This typically represents a costly waste since it results in consuming excessive material or overusing tools and equipment.

6)      Inventory:accumulation of raw material, work-in-process, and finished items. This is typical in push production systems functioning under fluctuations in demand and supplies.

7)      Defects:making defective products (reworked or scrapped) as well as delivering incomplete services. This should be based on understanding the difference between the defects’ definition and metrics in CTSs and CTQs.

Lean six-sigma terminology:

Over the years, LSS has developed its own terminology. Thus, before exploring key lean techniques, it is essential to be familiar with lean terminology:

a)      Batch size:the number of units accumulated and moved from one workstation to the next in the product flow.

b)      Bottleneck:the slowest operation in a production flow, which limits the throughput of the entire line.

c)       Cellular manufacturing:a group of resources or pieces of equipment arranged in the most efficient manner to process a product (or a family of products). In LSS, a cell layout is typically U-shaped with a 1-unit flow.

d)      Flow:the movement of product throughout the production system.

e)      Group technology:grouping into families products of similar processing needs.

f)       Just-in-time: providing what is needed, when it is needed, in the quantity in which it is needed.

g)      Kaizen (continuous improvement):a relentless elimination of waste and seeking improvement.

h)      Kanban:a visual signal (a card and an empty container) that triggers material withdrawal or parts manufacture in a pull production system.

i)        Lead time:the time between making an order and the order delivery date. The lead time of a process is determined by dividing the WIP by the process throughput.

j)        One-unit flow:a flow of products from one workstation to the next, one piece at a time (batch size = 1).

k)      Pull system:withdrawing material and producing parts once needed.

l)        Push system:producing units based on short- and long-term forecasts and pushing them to storage, waiting for orders from customers.

m)    Setup time:the time it takes to change over the production of one product to production of the next.

n)      Takt-paced production:setting and balancing a production line to run at the pace (takt time) required by customers.

o)      Takt time:a German word meaning musical beat or cycle; the desired inter departure time of units from the production line. It is calculated by dividing the total daily operating time by the total daily customer demand.

p)      Value:what the customer is willing to pay for a product or service.

q)      Value added:any activity that contributes to the value of a product or service.

r)       Value chain:elements and processes needed to develop a product or service.

s)       Value stream:actions that add value to a product or process.

t)       Value stream map:a high-level graphical representation of the value chain.

u)      Waste: tasks, requirements, and materials that do not add value to a product or service.

v)      WIP inventory:work-in-process parts in a production system.