Lean production. Part 2 + 6 Sigma
- Джимшер Челидзе
- May 31, 2024
- 13 min read
Updated: Jul 8, 2024
Content:
This is the 2nd post about lean manufacturing. In it we will look at some lean manufacturing tools, as well as what 6 Sigma and Lean 6 Sigma are.
Part 1 is available here
One of the lean manufacturing tools, along with SIPOC . Value Stream Mapping is a tool that visualizes the process of transforming raw materials into finished products sold to consumers. Its objects are material and information flows of resources, as well as time.
Creating Value Stream Mapping is divided into three blocks:
A production or process flow is a traditional flowchart in which, from left to right, the path of value creation is recorded, starting with the purchase of raw materials and ending with the shipment of products. If, in addition to the main process, there are additional or auxiliary ones, they are applied under the main one. In this way, the main tasks are separated from the secondary ones.
Information or communication flow - at the top of the value stream map, arrows depict information flows that occur in parallel with production. Both formal and informal data exchange are taken into account. Information flows are plotted on the map in free form, as they flow in reality.
Timeline and distances are lines that are drawn at the bottom of the map. The time line is divided into upper and lower parts. The lead time is displayed at the top - the waiting time. The cycle duration is shown below. Below the time line there may be another line, at the very bottom, showing the distances along which the product or personnel move within the process.
Simplified operation algorithm:
Step 1. Selecting a process for systematizing the value stream (preparatory)
Step 2: Value Stream Mapping Symbols
Step 3: Defining Process Boundaries
Step 4: Process Steps
Step 5. Adding information flows to the map
Step 6: Add data about each step of the process
Step 7. Inventory counting
Step 8. Adding process chronology - Timeline
Step 9: Future State Map
Step 10: Plan for Implementing Improvements
Useful links:
Video
Poka-yoke (poka-yoke) is one of the lean manufacturing tools. In Russian it sounds like “ protection from a fool .”
Anti-fool devices protect not just from errors, but from errors caused by human factors:
inattention
forgetfulness
carelessness
ignorance
tired
and even sabotage.
People make mistakes, and poka-yoke devices prevent them from making mistakes.
The operating principle of poka-yoke is characterized by:
100% verification coverage
fast feedback
low cost and simplicity.
Poka-yoke devices work on the principle of not missing a single defect.
They regulate the production process and prevent defects in one of two ways:
Control system - stops the equipment when an abnormality occurs, or blocks the workpiece with clamps so that it does not move further along the conveyor until it is processed as required. This is a preferable system because it is operator independent.
Warning system - sends a signal to the operator to stop the machine or correct the problem. Depends on the operator, so the human factor is not completely excluded.
Poka-yoke does not blame people for bugs , the goal is to find and fix weaknesses in the production system that made the bug possible.
Fool-proofing methods are divided into 3 levels in order of increasing effectiveness:
Level 1 - detects non-conformity of parts or products . The system detects the defective part, but does not discard it.
Level 2 – does not allow non-compliance. The system prevents the defective part from being processed at the next stage of the production process.
Level 3 - structural protection , for example, the product is designed in such a way that it is impossible to install or assemble it in an unintended manner.
Error Protection Principles
Elimination : This method eliminates the possibility of error by redesigning the product or process so that the problematic operation or part is no longer needed at all. Example : simplifying a product or connecting parts to avoid defects in the product or assembly.
Substitution : To improve reliability, you need to replace an unpredictable process with a more reliable one. Example : Using robotics and automation to prevent manual assembly errors. Use of automatic dispensers or applicators for precise dosing of liquid materials.
Caution : Design engineers must design a product or process such that it is impossible to make a mistake at all. Example : Design features of parts that allow only correct assembly; unique connectors to avoid incorrect cable connections; symmetrical parts that avoid incorrect installation.
Make it easier : Using certain techniques and grouping steps makes the assembly process easier to complete. Example : Visual controls that include color coding, part markings. An intermediate box that visually controls that all parts are assembled. Applying characteristics to parts.
Detection : Errors are detected before they move to the next production process so that the operator can quickly correct the problem. Example : Sensors in a manufacturing process that detect that parts are not assembled correctly.
Mitigation : Trying to reduce the impact of errors. Example : Fuses to prevent circuit overloads resulting from short circuits.
The emphasis of quality control is shifting from checking finished products for the fact of defects to preventing the occurrence of defects at each stage of production.
"House of TPS" was developed by Taichi Ohno and I. Toyoda specifically to make it easier to explain the Toyota Production System to employees and suppliers. According to the developers, the shape of the house (roof, columns and base) was used deliberately because it is understandable to everyone and symbolizes stability and solidity.
1st place - Inconsistency with Lean Manufacturing values
2nd place - Low priority for management
3rd place - Formalism (formal approach)
4th place - Following fashion
5th place - Problems of goal setting and vision of the future production system
6th place - Instrumental (technical) approach.
7th place - Lack of resources.
8th place - Disadvantages in organizing and managing the implementation of Lean Manufacturing
9th place - Poor basic conditions for employees
10th place - Lack of competencies
Pros of PSU
Disadvantages of Lean Manufacturing
Power/supply issues
Due to limited inventory in warehouses, lean manufacturing relies heavily on suppliers, who may supply products to the production process unreliably and intermittently. Issues such as employee illness, transportation delays, and supplier errors can be fatal. Sellers may be unable or even unwilling to supply parts or products on a tight schedule or in smaller quantities. Such requirements can place a burden on suppliers with overhead costs and create tensions that ultimately affect the production process and can lead to frequent changes in suppliers or even difficulty finding them.