Today, we are going to discuss the "Basic knowledge to ensure machine safetyHere is a note about "The
We need to design our machines to ensure their safety and to eliminate any hazards that may exist in the surrounding environment. For this safety, there are design rules set by each manufacturer and category of product to be manufactured, so it is important to design machines that are safe and free from hazards.Each designer's perception is different.We believe that this is a
In addition, it is not easy to ensure all the safety of a machine, since it is necessary to consider safety from the total perspective of basic design, structural mechanical design, electrical design (implementation), and software.
We design for safety becauseTo prevent even small disasters and ensure safe productionBut here, the mechanical design isWhere should we be aware of this?The following is a note of key words and brief explanations that you should at least understand about If you are a beginner in design, please refer to this page.
Safe design guidelines
First, we first identify keywords related to safety.
(1) Safety Methodology (Classification)
①-1: Fail-safe
In the event of a malfunction in a part of the machine.A method of operating on the safe side.
1-2: Backup
Stand behind the main function,A method of substituting a function in the event of a failure of the primary function.
①-3: Fail soft
In the event of a malfunction in a part of the machine.A method that does not stop the entire machine (function) even if the function declines.
(1)-4: Multiplexing
Machines (units) with the same (similar) functionalityMultiple installations, switching and selecting for use.
①-5: Failure diagnosis recovery
In the event of a malfunction in a part of the machine.A method that allows for rapid restoration of function.
①-6: Foolproof
In situations where people intervene.A method that makes it difficult to make a mistake in an operation or to be on the safe side even if a wrong operation is performed.
①-7: Delaying
Use a value lower than the rated value, etc.A method of designing with a safety margin.
①-8: Reduction of hazardous side failure
A technique to reduce the probability of a failure occurring that would lead to output on the hazardous side.
(2) Minimum awareness on the part of mechanical designers to ensure safe design
We expand on the above,Ensure machine safety at the design stage.In reality, however, there are times when we identify and correct hazards that we were not aware of while building the machine (especially where human intervention is involved, as unreadable behavior can occur).
General safety information is only in the abstract.However, from this point on, I would like to note some specific details that the mechanical design side should be aware of (at the very least, be aware of). However, this is my personal opinion, so please use it only as a reference.
②-1 Preventing Hazards Caused by Malfunctions During Operation
The concept is fail-safe. Designs are made with an awareness that if an abnormality or breakdown occurs during operation, the mechanism or structure should be designed to automatically become safe. Specific examples are
- Physically stops (stops) when an abnormality is detected
- Physically return (revert) when an anomaly is detected
- Visual and display signals when anomalies are detected
Fail-safe is a system that is designed to prevent failures. Some people think that fail-safes are a mixture of multiple systems and backup methods that substitute for something else in case of failure, but I think it is better to design fail-safes carefully with the awareness that the mechanism (unit) itself will take care of itself.
Of course, it is not absolutely necessary to do it by yourself. If you can do it by yourself, you should incorporate fail-safes, and if you cannot do it by yourself, you should use backups and multiple systems together.
2-2 Prevent operator error and actuator hazards
The concept is foolproof. This means designing products with an awareness of whether or not they will not move or cannot be operated when a worker mistakenly operates them.
For example, a press is a good example, and so are methods such as two-handed pressing. (because when one hand presses a button to operate it, it could crush the other)
A good way to protect people from machines that move by mistake is to move the controls away from each other to prevent accidental operation, or to cover the controls to give them a cushion. The main places where this foolproofing should be used are1 Situation where the operation cannot be stoppedThe following is used for
A machine that pushes with tremendous force cannot be stopped, nor can a machine that operates at a high speed be stopped suddenly.
However, this mechanically interferes with the worker's operation, so it is better to use an area sensor or a sensor system rather than a physical one.Light curtainThe main method used is to use sensing devices such as door open/close sensors. (If a person is in the area, the machine will stop and the switch will not respond.)
*For light curtains and area sensorsCorrect usage There are
②-3 More safety devices
I think the idea is to create a multiple system, which means that safety devices, etc. are double or triple-layered. If one part of the system breaks down, it could lead to a serious accident,In addition to the calculated safety factor, it is necessary to provide physical stoppers, etc.It is.
A familiar example would be a separate installation such as an electric actuator.Mechanical stopper and overrun sensorand the technique is to install multiple safety devices with sensors + physical stoppers.
Also, considering the possibility of failure when maintaining the lifted state with an air cylinder, etc., a separate drive stopper should be inserted while the lift is maintained, or a separate brake should be installed in case the brake on the motor breaks down, even if the motor + ball screw drive is used. (This is done by users who are strict about safety.)
As I write this, I think, "If you say that, you need it for everything," but the choice of this safety is based on whether it causes damage to people or not. If the machine broke down and fell far away, it is not necessary. If the effect of the partial breakage causes other serious failures and repair costs, then I think it is necessary to increase the number of safety devices.
2-4 Use properly selected and reliable purchased products
A surprising blind spot is this proper selection and use of reliable products.
One of the most common purchased products that machine designers are familiar with is the coupling that connects the motor to the drive unit. However, there are many types of couplings and they can be used for various purposes if you only look at the numerical values, which may lead to a serious accident due to wrong selection. (e.g., the coupling breaks).
Also,The frequency of machine breakdowns varies depending on the purchased products, steel, and materials used.and mechanical designers should pay the latest attention.
Finally.
I have written about ways to increase machine safety,As a designer, it would be good if I could design with safety in mind when assembling the machine as well as failures during operation.
To put it in simple terms.If heavy items are to be installed, design them so that they can be loaded and then installed.Such as. Like myself, many designers do not assemble machines themselves, so it is difficult for them to be aware of the dangers of installation and the difficulties of adjustment.
Since machines are fixed by pulling and pushing disparate parts together, distortion, large loads applied to certain locations, and the degree of assembly also affect the service life (failure frequency). In other words, whether optimal assembly can be guaranteed also depends on the mechanical designer's design.
I am not perfect in the least, so I will continue to do my best.
That's it.