Lean¶
A collection of notes about the Toyota way, Lean, Theory of Constraints etc. copied from Wikipedia and other sites
5S¶
Seiri Sort
Seiton Set in order
Seso Shine
Seiketsu Standardise
Shitsuke Sustain
Toyota Production System¶
Goal¶
Design out overburden (muri) and inconsistency (mura), and to eliminate waste (muda).
Types of waste¶
- Overproduction
- Time on hand (waiting)
- Transportation
- Processing itself
- Excess inventory
- Movement
- Making defective products
- Underutilised workers
Muda¶
Waste
Transport¶
Moving products that are not actually required to perform processing
Inventory¶
All components, work in process and finished product not being processed
Motion¶
People or equipment moving or walking more than is required to perform the processing
Waiting¶
Waiting for the next production step
Overproduction¶
Production ahead of demand
Over processing¶
Resulting from poor tool or product design creating activity
Defects¶
The effort involved in inspecting for and fixing defects.
Mura¶
Unevenness
Is avoided through just in time systems which are based on keeping little or no inventory. These systems supply the production process with the right part, at the right time, in the right amount, using first-in, first-out (FIFO) component flow. JIT systems create a pull system in which each sub-process withdraws its needs from the preceding sub-processes, and ultimately from an outside supplier. When a preceding process does not receive a request or withdrawal it does not make more parts.
Muri¶
Unreasonableness
Muri can be avoided through standardized work. To achieve this a standard condition or output must be efined to assure effective judgment of quality.
Concept¶
Just-in-time¶
Make only what is needed, only when it is needed and only in the amount that is needed
Jidoka¶
Autonomation, automation with a human touch
If an abnormal situation arises, the machine stops and the worker will stop the production line.
Autonomation aims to prevent the production of defective products, eliminate overproduction and focus attention on understanding the problems.
Poka Yoke¶
Any mechanism in a process that helps an equipment operator avoid (yokeru) mistakes (poka) and defects by preventing, correcting, or drawing attention to human errors as they occur
Continuous Improvement¶
We form a long term vision, then iteratively work towards it
Kaizen¶
We improve our business operations continuously, always driving for innovation and evolution
Genchi Genbutsu¶
Go to the source to find the facts to make correct decisions
Heijunka¶
Production levelling
Reduce unevenness which in turn reduces waste.
The goal is to produce intermediate goods at a constant rate so that further processing may also be carried out at a constant and predictable rate.
The right process will produce the right results¶
- Create continuous process flow to bring problems to the surface
- Use the 'pull' system to avoid overproduction (Kanban)
- Level out the workload (Heijunka)
- Build a culture of stopping to fix problems, to get quality right from the start
- Standardised tasks are the foundation for continuous improvement and employee empowerment
- Use visual control so no problems are hidden
- Use only reliable, thoroughly tested technology that serves your people and processes
Continuously solving root problems drives organisational learning¶
- Go and see for yourself to thoroughly understand the situation (Genchi Genbutsu)
- Make decisions slowly by consensus, thoroughly considering all options. Implement decisions rapidly (Nemawashi)
- Become a learning organisation through relentless reflection (Hansei) and continuous improvement (Kaizen)
Andon¶
The worker has the ability to stop production when a defect is found, and immediately call for assistance.
Work is stopped until a solution is found.
Stack light / Traffic light - Visual indicator of a machine state or process event
Nemawashi¶
An informal process of quietly laying the foundation for some proposed change or project, by talking to the people concerned, and gathering support and feedback. It is considered an important element in any major change, before any formal steps are taken and enables changes to be carried out with the consent of all sides.
Obeya¶
Large room
During the product and process development, all individuals involved in managerial planning meet in a great room to speed communicationand decision making.
Takt Time¶
Describes the required product assembly duration that is needed to match the demand. Often confused with cycle time, takt time is a tool used to design work and it measures the average time interval between the start of production of one unit and the start of production of the next unit when items are produced sequentially.
Theory of Constraints¶
Organisations can be measured and controlled by variations on three measures:
- Inventory - The money that the system has invested in purchasing things which it intends to sell
- Operational expense - The money the system spends in order to turn inventory into throughput
- Throughput - The rate at which the system generates money through sales
Constraints¶
A constraint is anything that prevents the system from achieving its goal. There is always at least one, but at most only a few, at any given time.
If a constraints throughput capacity is elevated to the point where it is no longer the systems limiting factor, this is said to 'break' the constraint.
Buffers¶
Buffers are placed before the governing constraint, thus ensuring that the constraint is never starved.
Buffers are also placed behind the constraint to prevent downstream failure from blocking the constraints output.
Buffers used in this way protect the constraint from variations in the rest of the system and should allow for normal variation of processing time and the occasional upset before and behind the constraint.
With one constraint in the system, all other parts of the system must have sufficient capacity to keep up with the work at the constraint and to catch up if time was lost.
Plant Types (VATI)¶
The plant types specify the general flow of materials through a system
V¶
Flow is one to many, such as a plant that takes one raw material and can make many final products.
The primary problem in V plants is 'robbing', where on operation (A) immediately after a diverging point 'steals' materials meant for the other operation (B). Once the material has been processed by A, it cannot come back and be run through B without significant rework.
A¶
Flow is many to one, such as where many sub-assemblies converge for a final assembly.
The problem in A plants is synchronising the converging lines so that each supplies the final assembly point at the right time.
T¶
Flow is many to many, similar to I plant (or has multiple lines), which then splits into many assemblies.
T plants suffer from both synchronisation problems of A plants and the robbing problems of V plants.
I¶
Material flows in a sequence of events in a straight line. The constraint is the slowest operation.