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The waterproof structure of the transparent window of the water meter
Keywords: water meter transparent window waterproof structure
First of all, to understand the types of waterproof structural design, structure and product features are roughly divided into three categories. 1: Dynamic 2: Solid State 3: Static
1. Dynamic as the name suggests, the waterproofing process is basically not used on such water meters.
2. The solid state can literally be understood, that is, the fixed structure is prevented. Such a water meter uses a transparent window portion, a speed reducer portion, an electronic module portion, and the like.
3. The static literal interpretation is relatively static, but there may be a folding action. The battery cover in the water meter is a static waterproof structure.
Today we focus on the transparent window section. As mentioned earlier, the window portion is a solid waterproof structure. It does not need to be disassembled before it is installed. Based on this feature, we can eliminate the combination of screwing and fastening and adding waterproof ring (high cost, troublesome assembly, unstable waterproof effect). Now we use ultrasonic welding and overmolding in actual production.
Let's talk about ultrasonic welding and overmolding.
1 The concept of ultrasonic welding: by applying high-frequency vibration to the thermoplastic parts to be welded, causing the surface of the plastic workpiece and the internal molecules to rub against each other, so that the temperature of the contact rises sharp enough to melt the plastic, the contact between the two welded parts A layer of melt is produced between the faces. When the vibration is stopped, the welded part is solidified by the pressure to complete the welding work.
Pay attention to the following points when performing ultrasonic welding: (1) The influence of materials. The plastic material is preferably made of raw materials. Do not add a nozzle material to avoid welding. (2) The surface of the plastic should be clean and free of mold release agents. (3) The welding surface cannot be surface treated. (4) Poor design of the ultrasonic line can also cause poor soldering and overflow. (5) Unstable fixtures for fixing plastics may cause ultrasonic welding deviations. (6) The matching of different kinds of plastic welding varies greatly
2 Secondary injection molding: It is a process of molding a certain plastic raw material in a plastic mold once, taking out the formed parts, and putting it into the secondary molding mold to inject the same kind or another plastic material. . More complicated is the multiple molding, so that the appearance and process of the plastic products meet the desired requirements.
Precautions for over-molding: (1) can not be mixed (if there is mixing, the injection will be layered, the strength will be reduced and broken); (2) look at what material, some materials must be dried before injection molding, otherwise it will There is silver wire; (3) The injection temperature is appropriately lowered because the material has been subjected to a high temperature and may be discolored by re-injection. (4) In the design, the two parts should be inlaid with each other.
From the above comparison, we can see that the ultrasonic welding process requires more attention and more complicated operations in actual production. If one of them is not controlled, it will cause problems. More operational processes are also produced in production. And the overmolding is much simpler for our production. It is only necessary to use one worker to operate once during injection molding. Other precautions After the mold is controlled, there will be no more problems in the future. As for the waterproof effect, both can be trusted. Finally, it can be concluded that the waterproof part of the transparent window of the water meter is most suitable for overmolding.
 Li Huilai, Jin Zhi. Product Structure Design. Electronic Industry Press, 2014.
 Editorial Board of Mechanical Engineers Manual. Mechanical Engineer's Handbook. (Third Edition)) Mechanical Industry Press. 2007.
Ultrasonic water meter
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