1 Introduction The tools and products we use in daily production and life range from the base of the machine tool to the outer casing of the machine, to a small screw, button and shell of various household appliances, all of which have a close relationship with the mold. The shape of the mold determines the shape of these products, and the quality and precision of the mold determines the quality of these products. Because of the different materials, appearance, specifications and uses of various products, the mold is divided into casting molds, forging dies, die-casting dies, stamping dies and other non-plastic molds, as well as plastic molds. In recent years, with the rapid development of the plastics industry and the continuous improvement of the strength and precision of general and engineering plastics, the application range of plastic products is also expanding, such as: household appliances, instrumentation, construction equipment, automobile industry, day In many fields such as hardware, the proportion of plastic products is increasing rapidly. A well-designed plastic part can often replace multiple traditional metal parts. The trend of plasticization of industrial products and daily-use products is on the rise. 2, the general definition of the mold: in industrial production, using a variety of presses and special tools mounted on the press, through the pressure of metal or non-metallic materials to produce the desired shape of parts or products, this special tool is collectively referred to as the mold . 3. Description of the injection molding process: The mold is a tool for producing plastic products. It consists of several sets of parts with a molded cavity. During injection molding, the mold is clamped on the injection molding machine, the molten plastic is injected into the molding cavity, and is cooled and shaped in the cavity, and then the upper and lower molds are separated, and the product is ejected from the cavity through the ejection system to leave the mold, and finally the mold is closed. For the next injection, the entire injection molding process is cyclic. 4, the general classification of mold: can be divided into plastic molds and non-plastic molds: (1) Non-plastic molds include: casting molds, forging dies, stamping dies, and die-casting dies. A. Casting mold, tap, cast iron platform B. Forging die?? car body C. Stamping die?? computer panel D. Die-casting mold?? Super alloy, cylinder block (2) Plastic molds are further divided according to the production process and production products: A. Injection molding machine? TV case, keyboard button (the most common application) B. Blowing mold??Beverage bottle C. Compression molding die? Bakelite switch, scientific porcelain dishes D. Transfer molding die?? E. Extrusion molding?? glue hose, plastic bag F. Thermoforming mold?? Transparent molded packaging shell G. Rotary molding die?? Soft plastic doll toy ◆ Injection molding is the most common method used in plastic processing. The method is applicable to all thermoplastics and some thermosetting plastics. The amount of plastic products produced is far beyond the reach of other molding methods. As one of the main tools of injection molding processing, the injection mold is in the quality precision, manufacturing cycle and injection molding process. The level of production efficiency and other aspects directly affects the quality, output, cost and product renewal of the product, and also determines the ability and speed of the company's response in the market competition. ◆The injection mold is composed of several steel plates combined with various parts, which are basically divided into: A forming device (die, punch) B positioning device (guide column, guide sleeve) C fixing device (I-shaped plate, code die pit) D cooling system (water hole) E constant temperature system (heating tube, heating line) F runner system (唧 nozzle hole, runner groove, runner hole) G ejection system (thimble, top stick) 5, according to the different types of casting system can be divided into three categories: (1) Dashuikou mold: The runner and gate are on the parting line, and the product is demolded together when the mold is opened. The design is the simplest, easy to process, and the cost is low, so many people use the large nozzle system. (2) Sluice nozzle: The runner and gate are not on the parting line, generally directly on the product, so it is necessary to design a set of nozzle parting lines. The design is more complicated and difficult to process. Generally, it depends on the product requirements. Sluice system. (3) Hot runner mold: This type of mold structure is basically the same as the fine water nozzle. The biggest difference is that the flow channel is in one or more constant temperature hot runner plates and hot nozzles, no cold material release, flow path and pouring. The mouth is directly on the product, so the flow channel does not need to be demoulded. This system is also called the waterless port system, which can save raw materials, is suitable for the case where the raw materials are expensive and the product requirements are high, the design and processing are difficult, and the mold cost is high. The hot runner system, also known as the hot runner system, is mainly composed of a hot sprue bush, a hot runner plate, and a temperature-controlled electric box. Our common hot runner systems are available in single-point hot gates and multi-point hot gates. The single-point hot gate uses a single hot sprue sleeve to directly inject the molten plastic into the cavity. It is suitable for a single-cavity single-gate plastic mold. The multi-point hot gate branches the molten material to each through a hot runner plate. The hot runner is re-entered into the cavity, which is suitable for single-cavity multi-point feeding or multi-cavity molds. ◆The advantages of hot runner system (1) Water-free material, no post-processing is required, which makes the whole molding process completely automatic, saves working time and improves work efficiency. (2) The pressure loss is small. The hot runner temperature is equal to the temperature of the injection nozzle of the injection molding machine, which avoids the surface condensation of the raw material in the runner and the injection pressure loss is small. (3) Repeated use of the nozzle material will degrade the performance of the plastic, and the use of the hot runner system without the nozzle material can reduce the loss of raw materials and thus reduce the product cost. The temperature and pressure in the cavity are uniform, the stress of the plastic part is small, and the density is uniform. Under a small injection pressure, a shorter molding time, the injection molding is better than the general injection molding system. For transparent parts, thin parts, large plastic parts or high-demand plastic parts, it can show its advantages, and it can produce larger products with smaller models. (4) The hot nozzle adopts standardized and serial design, and is equipped with various nozzle heads for easy interchangeability. The unique design and processing of the electric heating ring can achieve uniform heating temperature and long service life. The hot runner system is equipped with a hot runner plate, a thermostat, etc. The design is exquisite, diverse, easy to use, and the quality is stable and reliable. ◆ Inadequacies in the application of hot runner systems (1) The overall mold closing height is increased, and the overall height of the mold is increased due to the addition of hot runner plates. (2) Thermal radiation is difficult to control. The biggest problem with hot runners is the heat loss of the runner, which is a major issue that needs to be solved. (3) There is thermal expansion, and thermal expansion and contraction are issues that we should consider when designing. (4) The cost of mold manufacturing increases, and the price of standard accessories for hot runner systems is high, which affects the popularity of hot runner molds. ◆The companies that provide hot runner standard parts are: DME, HASCO, HUSKY, EOC, FULLY, MASTER-TIP, INCOE and other companies. The advantage of the plastic centrifuge tube is that it is transparent or translucent, its hardness is small, and the gradient can be taken out by the puncture method. The disadvantage is that it is easy to deform, has poor corrosion resistance to organic solvents, and has a short service life.
Plastic Centrifuge Tubes have caps, which are used to prevent sample leakage, especially when used for radioactive or highly corrosive samples. It is very important to prevent sample leakage; the tube cap also has a function to prevent sample volatilization. And support the centrifuge tube to prevent deformation of the centrifuge tube. When choosing this point, you should also pay attention to check whether the tube cover is tight, and whether it can be tightly covered during the test, so as to achieve the inversion without leakage;
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