In industrial design, in order to avoid the user's operating errors causing machine or personal injury (including unconscious movements or subconscious malfunctions or careless body movements), preventive measures will be taken against these possible situations, which are called prevention measures. stay. Today let's talk about the importance of foolproof design.
This is an example of plug and socket foolproofing. As shown in the picture below, there is a raised place on the socket. Its main function is to prevent the plug from being inserted backwards.
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What is fool proofing?
Fool-proofing is a design method that prevents stupid people from doing wrong things, so that even stupid people will not do wrong things, so that mistakes will never happen.
In the mold design, if the insert is not foolproof, if it is installed backwards, the product structure will be incorrect; if the mold core is not foolproof, if it is installed backwards, the mold will be crushed. This type of case is a huge mistake in mold and injection molding factories and must be avoided through fool-proof design.
More specifically, the "foolproof method" is:
1) It has a structure that does not cause errors even if there is human negligence─it does not require attention.
2) It has a structure that even a layman can do without error - no experience or intuition is required.
3) Having a structure that will not go wrong no matter who is working or when - no specialized knowledge or high skills are required.
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The role of fool proofing
During the operation process, operators will make mistakes due to omissions or forgetfulness from time to time. The problems caused by this account for a large proportion. If foolproof methods can be used to prevent the occurrence of such mistakes, the quality level and work efficiency will be improved. It will be greatly improved.
1) Fool-proofing means "getting things done right the first time." Fool proofing uses a series of methods and/or tools to prevent mistakes from happening, with a certain result being getting things done right the first time.
2) The fool-proof method means "fool-proofing" of the process "even if there is human negligence or a layman can do it without making mistakes, that is, no special experience or special attention is required." Fool-proofing uses a series of methods and/or tools to prevent human errors from occurring, so that unless intentional, nothing will be done wrong.
3) Improve product quality, reduce waste caused by inspection, and eliminate rework and the waste caused by it. Fool-proofing means "getting things done right the first time", and the direct result is an improvement in product quality. Fool-proofing eliminates the waste of inspections. Defects are eliminated, which results in a reduction in the number of reworks and the waste of time and resources due to rework is eliminated.
4) Implement automation and improve efficiency. The fool-proof method reduces the reliance on human subjective judgment, tries to automate the process, reduces the possibility of human error, and improves labor efficiency.
5) Ensure safety. The fool-proof method makes full use of various IE techniques to ensure that even if a person makes a simple mistake, the mechanism can automatically recognize the correctness of the action and ensure the safety of man and machine.
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Forget the heavy price of foolproofing
1. The story begins
I remember that time, when we were making a brand of computer speaker casings, the mold production cycle showed 103,808 molds. Due to the high product requirements, the molds were required to be cleaned, and the ejector pins, inserts, row positions, and partings were required to be maintained before each production. surface, cooling water lines, etc. After the maintenance is completed, the machine will be produced according to the original plan until the order is completed, a total of 20,000 PCS.
2. Something went wrong - 700,000 was gone
One month later, the company's assembly department had assembled the product into a finished product and was about to ship it. However, something unexpected happened. During the OQC inspection, relying on past experience and keen insight, it was discovered that "the product LOGO was marked backwards." As shown below.
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Due to assembly requirements, most internal parts were covered with AB glue, leaving little room for rework. It was estimated that the entire batch of products was worth more than 700,000 yuan, resulting in heavy losses. What's the problem?
3. Summary of the meeting - no mold prevention was done
After the company leaders learned of the incident, they launched an investigation into the incident. "The logo on the plastic shell is reversed. It must be a mold problem," a quality engineer said. The manager of the mold department immediately organized a meeting with personnel: 1) Investigate who installed the mold? 2) How to avoid making the same mistake next time?
After pulling out the mold maintenance order that afternoon, I found that it was an old employee with three years of service in the company. Because the molds were not fool-proofed and the company only relied on the experience and intuition of the mold installer to make mistakes, the company would face an economic loss of 700,000 yuan. The main reason was that the molds were not fool-proofed.
In the field of mold design, when designing a set of molds, how can we prevent errors from happening or minimize the chance of errors? How to be fool-proof?
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Fool-proof mode
Foolproofing adopts different foolproofing modes for different processes and error categories, which are:
1. Tangible foolproofing
The tangible error-proofing mode is a hardware error-proofing mode based on the material attributes of products, equipment, tools and operators. For example, the sensor switch in a rice cooker is a tangible POKA-YOKE error-proofing mode. If water is not added to the rice cooker, the heating switch cannot be set to the heating position. Only when water is added can the heating switch be turned to the heating position.
2. Orderly prevention
The orderly foolproof mode is a foolproof mode that monitors the order of process operation steps or prioritizes error-prone and forgettable steps before working on other steps.
3. Grouping and counting foolproofing
Grouping and counting error-proofing modes are error-proofing modes that prevent work errors by grouping or coding.
4. Information strengthens foolproofing
The information-enhanced fool-proof mode achieves traceability by transmitting specific product information between different locations and operators.
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Fool-proof level
According to the fool-proof effect of the fool-proof device, it can be divided into 3 levels:
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Principles of implementation of foolproof law
The following are a few basic foolproof rules. Following these rules can effectively prevent work errors.
1. The principle of ease
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2. The principle of simplicity
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3. Safety principles
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4. Automation principles
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example:
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How to be foolproof
1. Fool-proof design
The causes of errors are fundamentally eliminated so that errors never occur.
1) Use the elimination method to achieve it.
2) Use "asymmetric shape" to achieve it.
3) Using the "synchronization principle", multiple actions need to be executed together to be completed. Example: Operations when opening a bank vault. Example: Manual operation of a punch press (two-hand switch).
4) Use "sequential" actions to complete. Example: elevator door.
5) Principle of extreme positioning. Example: Hydraulic lift limit contact stop switch.
6) Use interactive actions to complete. Example: chain organization.
2. Isolation principle to prevent fooling around
Separate different areas to protect certain areas from causing danger or errors. The isolation principle is also called the protection principle.
Example: A protective cover for an electric circular saw to prevent the saw from getting into your hands. Car seat belts and helmets when riding motorcycles. Add cardboard to reduce product damage during transportation. Swipe your card to enter.
3. Process automation and foolproofing
Various optical, electrical, mechanical, mechanical and chemical principles are used to limit the execution or non-execution of certain actions to avoid errors. These automatic switches are very common nowadays and are a very simple automation application.
1) Control by "buoyancy". For example: There is a floating ball in the water tank of the toilet. When the water rises to a certain height, the floating ball pushes the switch lever and cuts off the water source.
2) Completed by "weight" control. Example: When the elevator is overloaded, the door cannot be closed, the elevator cannot go up or down, and the warning bell also sounds.
3) Completed by "light" control. Example: In an automatic camera, if the light is insufficient, the shutter cannot be pressed.
4. Warning principle to prevent fools
If an abnormal phenomenon occurs, various "warning" signals can be displayed in sound, light or other ways to avoid errors.
Example: When the car speed is too high, the warning light will light up. The seat belt was not fastened, the door was not closed, and the warning light came on. When operating the computer, if a key is pressed incorrectly, a warning sound will sound. When there is an error in the English word in the word document, the page will automatically be reminded with a red line.
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How to effectively implement process foolproofing
1. Regarding foolproofing, the following concepts should be established
1) Self-inspection and mutual inspection are the most basic, primitive, but quite effective error prevention methods.
2) Poka-yoke devices do not require a large investment of resources or a high level of technology.
3) Any operation or transaction process can be pre-designed with error-proofing technology to prevent human errors.
4) Zero defects can be achieved through continuous process improvement and error prevention.
5) Poka-yoke should be based on prevention, and error-proofing methods during each process operation should be considered at the beginning of the design.
6) Consider error-proofing methods in all areas where problems may arise.
Adhering to the above concepts to carry out process management can effectively implement the foolproof method.
2. General steps for implementing the foolproof method
1) Determine product/service defects and collect data;
2) Trace the discovery process and production process of defects;
3) Confirm the work instructions for the defect generation process;
4) Confirm the differences between the actual work process and the work instructions;
5) Confirm whether the following problems exist in the process:
6) Analyze the causes of defects;
7) Analyze the causes of homework errors;
8) Design error-proofing devices or error-proofing procedures to prevent or detect similar errors;
9) Confirm the error-proofing effect and make process adjustments if necessary;
10) Continuous control and improvement.
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Process Foolproof Application Cases
Example 1. Anti-fool device for power tool packaging
Problem: Power tools, accessories, instructions and certificates are delivered to customers as an integrated package, but missing or incorrect packaging always occurs, and the effect is not obvious after training and punishing packaging and wiring employees.
Example 2. Improvement of anti-fooling in mixed holes in mobile phone case production
After reading the article, we better understand the importance of fool-proof design. If the company had made fool-proof molds in advance, it would not have faced an economic loss of 700,000 yuan. What is lost is not only money, but also the company's reputation.
