With the continuous advancement of scientific and technological progress, more and more new materials are widely used in various fields, some comprehensive performance of plastic is also a switch socket products have been widely used. The plastic is used almost exclusively on most parts except metal functional, contact, and fixing screws. Such as plastic installation of the structure of the switch products, the amount of plastic parts of the product accounted for more than 85%; steel installation structure of the switch products, plastic parts accounted for more than 50%. With the safety, environmental protection, energy saving and other requirements of the gradual increase in the application of these products on the plastic parts will have more and more deep understanding.
1, applied in the switch socket on the characteristics of plastic
(1) light weight. Light weight is the common pursuit of all consumer goods target, the general density of plastic between 0.8 to 1.5, ABS is about 1.1, PA is about 1.15, PC is about 1.2, and ordinary metal material density between 3 to 10, aluminum The material is about 2.7, the steel is about 7.8, the copper is about 8.9, so the plastic is one of the most effective ways to realize the product light weight.
(2) comprehensive performance superior. Plastic has good dimensional stability, chemical resistance, thermal stability, impact resistance and so on.
(3) easy to shape, high precision parts. Plastic can make the shape of complex parts processing simple, the use of injection molding parts, different shapes, complex shape. Forming a short cycle, a high degree of automation, precision is guaranteed. Such as complex structure of the shape of the fixed frame and rear seat, with plastic can be a plastic injection molding.
(4) strong corrosion resistance. Local damage will not be corrosive, acid, alkali, salt and other corrosion resistance is better than metal, very suitable for large occasions in the use of pollution.
(5) good heat resistance. The key indicator is to measure the degree of heat resistance of the switch socket products, that is, how much the product will be deformed, once the product deformation will not work properly. The normal use of the switch socket environment is generally indoors, the temperature does not exceed 30 ℃, if you consider the product back seat in the work of electricity will produce a little heat, the maximum temperature does not exceed 70 ℃, and can use the switch socket products in the plastic minimum heat Deformation temperature is higher than 70 ℃, the minimum is about 100 ℃, so the normal use will not produce heat distortion.
(6) good anti-aging properties. This indicator is a measure of the actual use of the product after a few years in the natural environment will happen some changes, the standard switch socket products must pass anti-aging test:
Store the product in a 70 ° C heating chamber for 7 days (168 hours) and store at least 4 days (96 hours) in a constant temperature and humidity chamber at room temperature and relative humidity between 45% and 55%. After the test , The product shall not be damaged, the product may not have visible cracks, the material may not stick sticky slip.
(7) good flame retardant properties. This is an important indicator of the fire performance of the switch socket.
On the issue of plastic flame retardant, in the past there have been consumers directly with the lighter to ignite the product to determine whether the flame resistance is qualified, this approach is unscientific, the national standard is to use glowing wire test to verify the judge.
The purpose of the glow test is to ensure that the electrothermal test wire does not cause the insulating material to ignite under specified conditions or to ensure that the insulating material parts are lit by the hot wire under specified conditions but only for a limited period of time Burning, and the fire will not be due to flame or burning particles fall to the use of silk paper covered on the spread of wood.
Tests must be carried out using the glow-wire test device specified in the national standard: Insulation material parts necessary for holding the current-carrying parts and the grounding circuit components in the normal position at a test temperature of 850 ° C; for holding the ground terminal in the mounting box Insulated material parts at normal locations with a test temperature of 650 ° C.
(8) good impact resistance.
The switch socket product must be tested by an impact test device specified in the national standard, and the test specimen must not be damaged, especially if the live parts can not be touched.
(9) plastic materials, environmental protection, energy saving, can be recycled several times, the material cost is relatively low.
2, from the functional points, the plastic switch socket for more decorative parts, structural parts, sports parts
(1) decorative pieces, such as panels, borders, decorative trim and so on. As shown below:
These parts do not directly contact with the conductive parts, can not afford the role of fixed support, mainly from the decorative effect, that is, the standard said "to keep the current-carrying parts in the normal position is not necessary insulation material." Usually use PC, ABS material, to meet the 650 ℃ glow hot test and 70 ℃ heat test can be. General general-purpose ABS can also meet, but by the ordinary ABS anti-ultraviolet and other performance limitations, in order to avoid long-term use after the color change and other defects, most or choose PC or PC / ABS synthetic materials.
Surface Decorations In order to pursue a variety of color combinations, you can produce different plastic colors by adding additives, you can also save the painting process, but the color of plastic parts directly produce the lack of some metal texture, shiny.
(2) structural parts, such as fixed frame, rear seat and so on.
These parts are directly in contact with the current-carrying parts, that is, the "insulating material parts necessary to keep the current-carrying parts in the normal position" as the standard, usually PC and PA, and PC / ABS synthetic materials, Glow wire test and 125 ℃ heat resistance test.
Rear seat color is usually white, black, in order to pursue new, there are some options "semi-transparent black". The surface of the matte fine grinding treatment, so that the process gate, shrinkage marks, injection molding, welding lines and other process defects are not obvious.
These parts are to prevent stress cracking defects. Previously there was a case, because the product design reasons, a product back seat to be selected high mobility of plastic, after a period of time after the use of parts cracking, the multi-analysis to determine the batch of materials in the production of large internal stress, stress cracking Resulting in, back seat off, the product can not be used normally.
Depending on the composition of the plastic, the properties of the plastic can be made by adding different fillers, plasticizers and hardeners to change the mechanical strength and processability of the material. If the mounting frame of a plastic structure can not be designed to have good rigidity due to structural design reasons, appropriate PC + glass fiber materials can be used to improve the strength and stiffness of the entire product.
(3) moving parts, such as switch keys, dial, socket protection doors.
Although these parts do not directly contact with the power parts, but it is to achieve the basic function of the product, it is critical parts, must meet the 850 ℃ glow test and 125 ℃ heat test. Usually use PC, PA materials, but also the use of PC / ABS synthetic materials.
Plastic has the function of absorbing and attenuating vibration and noise, improving the use of comfort. Such as with the switch button action with the pieces, usually with plastic, and appropriate in the design of some buffer cushioning structure, to avoid a large area of contact, can make the button work, and the installation of the base between the issue of crisp sound, Produce noise that affects people's normal working life.
Switch movement frame, usually use PC or PA material. In the past, there are occasional feedback to melt the adhesion phenomenon, analysis is not a material problem, the actual load is too large or concentrated for the fluorescent load, instantaneous start current is too large, due to excessive heat. Such as conference room switch control multiple sets of fluorescent lamp, with the switch of the air conditioning socket, etc., can be appropriate to change the pressure to increase the compression spring, increase the contact pressure and other methods to improve.
Socket protection door. Selection of PA, more is added after the modified glass fiber PA, the main varieties are PA6 + glass fiber, PA66 + glass fiber, enhanced flame retardant PA6. PA material itself is very high wear resistance, and more self-lubricating function, low coefficient of friction, so no lubrication can be normal operation, to meet the general occasions on the protection of the door movement flexibility requirements, such as want to get special lubrication effect, Can be added in the PA a small amount of sulfide, supplemented by appropriate grease, can effectively improve the lubrication effect, both to ensure flexibility and can meet the requirements of the socket product standard to prevent the requirements of unipolar insertion test.
(4) in the use of the process, also need to note the following:
In order to improve production efficiency, mold design and more choice of the same part of a multi-cavity, two or three parts combined with a mold, or even the same product on the adjacent two parts designed as a whole, can effectively control the number of molds, Injection molding and product assembly card loading time, to a large extent improve the production efficiency, but also save energy consumption.
In order to adapt to the production of automated mass production, the mold design priority channelless injection molding, priority point gate (shear gate), unless the surface requirements must be selected higher edge gate (horn gate) to ensure quality.
Plastic surface can be treated with frosted as far as possible without the choice of high light treatment, surface scrub treatment can effectively cover a lot of injection defects, such as welding lines, rhyolite, cold spots, shrink marks and so on. Matte surface for injection automation, assembly automation, fast logistics are very favorable, injection molding machine can be directly in contact with the suction cup, injection molding can be directly into the tray to collect collectively, parts flow through the automatic assembly of automatic vibration disk movement is not easy to scratch , In the entire logistics process even if the appropriate friction will not affect the surface quality.