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Those things in the automobile industry column
See the latest information about Model Y from Detroit Engineering Consulting Company from the garage No.42 in Chetan Dhaka, which mentioned the plastic buckle. In fact, there is no such classification method as ordinary and non-ordinary, only metal and nonmetal, cheap and not cheap. Of course, there are many materials under the metal and nonmetal buckles. So let's discuss the topic of buckles and why some products like to use metal buckles and some products like to use plastic buckles. What factors are related to whether the belt buckle can be used after being removed many times?
Buckle is a mechanism that one part is embedded with another part or locked integrally, which is usually used for the connection between plastics or between plastics and metals. If it is a metal-to-metal connection, buckles are generally not needed. The reason why the buckle is selected for connection during vehicle assembly is because the clamping process is very simple, and the well-designed clamping process hardly needs auxiliary tools. If only some parts are designed as a whole, on the one hand, they are too bulky to be transported, and on the other hand, if some sub-parts need to be assembled inside the parts, it is not convenient to operate, so simply designing several sub-parts to be clamped together is convenient for transportation, and the sub-parts are disassembled, thus saving costs.
More than 70% of ordinary belt buckles are made of plastic materials, while less than 30% are made of metal materials. This is because:
1. The density of plastic is much lower than that of metal. Although we can't see it with the naked eye, there are actually hundreds of large and small buckles on the whole car. If these buckles are made of metal materials, the total amount will reach several kilograms, and the use of plastic materials will reduce part of the weight.
2. The molding process of plastic buckle is much simpler. Most plastic buckles are injection molded at one time. Of course, with the development of technology, considering the noise reduction factor, many belt buckles are now cushioned by double injection molding of EPDM material at the front contact point. However, the process of metal buckle is complicated, including cutting, punching and bending, as well as surface treatment. As can be seen from the screenshot, such a simple metal buckle needs seven different tools to operate in turn through the program, while injection molding only needs one mold and one step, so the molding process of plastic buckle is simpler.
3. The cost of plastic buckle is lower. Because of the simple process, the processing cost is definitely lower, complicated equipment and fixtures are not needed, and the cost of plastic materials is lower than that of metal materials.
4. Plastic buckle is more environmentally friendly than metal buckle. Because plastic materials have corrosion resistance, surface treatment is not needed. However, the metal buckle is easy to rust or be corroded by oil stains or chemical reagents on the car, so its surface must undergo strict surface treatment, and some even go through 3~4 processes, each of which will release waste liquid that pollutes the environment. In addition, the scrap of plastic buckle is easy to be directly recovered, while the scrap of metal buckle during punching is a waste, which is almost impossible to be directly recovered, and it takes many processes to become usable metal.
5. Plastic buckle is more insulated than metal buckle. Especially when it comes to the connection of electrical equipment, plastic buckle is the only choice.
6. The toughness of plastic buckle is better than that of metal buckle, so it is not easy to produce abnormal sound.
7. The section damage of plastic buckle is lower than that of metal buckle, so in some areas involving collision collapse or airbag explosion, plastic buckle is the first choice.
8. In the process of repeated assembly, the plastic buckle has less damage to the hand-held part, which can better ensure the strength of the hand-held part.
Seeing the advantages of so many plastic buckles, isn't it amazing to blow them? In fact, plastic buckles also have some disadvantages, such as:
1. The mold of plastic buckle belongs to precision molding mold, and the mold cost is not low;
2. Plastic parts have the defects of deformation and size fluctuation, especially under the production process of one mold and multiple cavities, it is difficult to ensure the consistency of each cavity, so the requirements for equipment and technology are very high;
3. The plastic material will also be affected by environmental factors, and its performance will change in the environment where temperature and humidity change alternately, especially the buckles around the engine and exposed to the outside air;
4. Although the toughness of plastic exceeds that of metal, when plastic is connected with metal, the sharp metal punch will destroy the shape and size of plastic and lose its original function after repeated disassembly;
Therefore, in some special parts, especially when plastic and metal are clamped, metal buckles will still be chosen as the first choice for connection.
So when designing the buckle, is it all right as long as the above conditions are met? Not at all. The two most important factors to consider when designing buckles are tension and abuse force. The buckle is put into use on a large scale because it is easy to disassemble. Imagine that if we don't have the buckle, almost every time we disassemble the machine, we will scrap a part. This cost is obviously too uneconomical. With the buckle, we can put it back after disassembly and use it next time. Therefore, it is required that the buckle and surrounding parts will not be damaged after repeated disassembly within a certain number of times, and at the same time, it can be easily disassembled during disassembly and installation, which is convenient for operation. However, if it is too easy to disassemble and install, the fastening function cannot be realized, and the vehicle will make abnormal noise or automatically separate when driving, which is very harmful to the driving experience and safety protection. Therefore, the amount of constraints in this clamping process is very elegant, too many constraints, too difficult to assemble and disassemble, and even damaged, and the effect of reuse cannot be achieved. If there are too few constraints, abnormal sound and falling off will not achieve the fastening effect. The size of this constraint depends on the drawing force to be verified, and the range of installation and disassembly forces should be specified. The number of reuse can be tested by abuse experiment. Of course, the abuse force test is not only related to the size of the buckle, but also related to the performance of the material. However, both metal buckles and plastic buckles will encounter problems in use, but it must not be said that metal buckles are better than plastic buckles, and plastic buckles are better than metal buckles. The buckle of each material needs to adjust various parameters according to the relationship and characteristics of assembly. The buckle made of any material is not omnipotent, and the technical details involved may not be written into a book.
At present, the design and technology of both plastic and metal buckles in China are still in a backward stage, and the key technologies and patents are still in the hands of companies such as Aramonde, ITW and TRW. Their design level and material formula are in the leading position in the industry. Even if there are domestic suppliers who can counterfeit, on the one hand, it involves infringement, on the other hand, the level of CPK is not ideal, on the other hand, the reliability is even worse, and finally it is not necessarily cheaper than imported ones.