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12 basic knowledge of plastic mold

date：2023/08/10

     01 Nozzle melt is generally injected into the nozzle from the nozzle, but some abrasive tools, the nozzle is part of the abrasive tool, because it widens to the bottom end of the abrasive tool. There are also two key types of nozzles: open sniper nozzles and closed nozzles. In injection molding production, open nozzles should be used more often because they are both cost-effective and less likely to stay. If the plastic machine is equipped with a pressure-relief device, even the lower viscosity melt adhesive can also be used for this type of nozzle. Sometimes it is necessary to use a closed nozzle. This type of nozzle is used as a throttle valve to block the plastic shade in the injection cylinder. Ensure that the nozzle is properly connected to the nozzle sleeve. The top hole is slightly finer than the nozzle sleeve, which makes the nozzle easier to withdraw from the grinding tool. The hole of the nozzle sleeve is larger than that of the sniper nozzle, that is, the half meridian of the nozzle is thinner than the nozzle nozzle by 0.5 mm.
02 The residue of the filter device and the plastic of the combined nozzle can be eliminated by the filter device of the malleable nozzle, that is, the melting and the plastic pass through a wireless channel, which is separated by the insert into a narrow indoor space. Such small and small gaps can remove residues and improve the mixing of plastics. Thus widening the opening back, fixed fixed switching valves can be applied to achieve a stronger mixing effect. This equipment can be installed between the injection cylinder and the nozzle to carry out the work of separating and remixing the glue, most of which is to make the melting pass through the wireless channel of the stainless steel plate.
03 Exhaust pipe Some plastics must be in the exhaust pipe of the injection cylinder during the injection molding process to let the vapor out. In most cases, this vapor is only a gas, but it may be water or single-molecule vapor that is melted and released. If this vapor can not be released, the vapor will be reduced by the melt and sent to the abrasive tool, it will expand and generate bubbles in the commodity. To discharge the gas before it reaches the injection nozzle or grinding tool, reducing or reducing the diameter of the screw root of the extruder can relieve the pressure of the melt in the injection cylinder. Here, the vapor can be discharged from the hole or hole in the shot cylinder. Subsequently, the diameter of the screw root of the extruder is expanded, and the melt of devolatile organic compounds is oriented toward the nozzle. The plastic machine equipped with this equipment is called the exhaust pipe type plastic machine. This type of exhaust pipe plastic machine should have a very good exhaust system for the catalytic reaction burner to remove the harmful vapors.

1, pay attention to the use of abrasive order
Even high-quality hardware mold accessories need to use abrasive in a certain order when grinding, which must be from large particles to small particles, from coarse abrasive to fine abrasive. And in order to avoid the phenomenon of "relief".

2, pay attention to the correct use of abrasive
In order to avoid scratches on the surface of the hardware mold accessories, only the same particle size of abrasive can be used in the same lashing tool, and the surface of the hardware mold accessories must be carefully cleaned before each particle size change to avoid residual large-particle abrasive damage to the accessories in the next process.

3, pay attention to the correct operation of different particle size grinding
When the hardware mold accessories grinder grinds the precision mold accessories, when the next particle size grinding process is converted, the direction of the grinding will be about thirty degrees from the direction of the last grinding, because it is less likely to appear scars. If scars appear during the conversion operation, they should be fully trimmed to remove the pits.

04Improve the efficiency of the condensing steam type in order to obtain high-quality melt glue. The plastic must be heated or melted uniformly, and it must be sufficiently mixed. Only the proper extruder screw can be properly melted and mixed, and it has sufficient working pressure (or condensing type) in the shot cylinder to facilitate the consistency of mixing and heating. The frictional resistance of the lift pump oil can cause a condensing type in the sniper feed master cylinder. However, the screw of the extruder has to be calibrated for a longer time, so there is a lot of damage and expense in the software of the drive system of the plastic machine. As far as possible to maintain the condensing type, and gas barrier, it must also be consistent with the melt temperature and mixing level
05 Restriction valve No matter which type of extruder screw is used, the top of the extruder is generally equipped with a restriction valve. In order to prevent the plastic from being discharged from the nozzle, it will also be equipped with pressure relief (reverse cable) equipment or a very sniper nozzle. If applying abortion supply and marketing, it must be regularly maintained, because it is a key part of the sniper master cylinder. At this stage, the power switch type nozzle is not widely used, because the sniper nozzle weapon equipment is very easy to leak plastic and dissolve. At present, each plastic is marked with the type of sniper nozzle available.
06 Extruder screw reversing (reverse cable) Many plastic machines are equipped with extruder screw reversing or suction equipment. When the screw rotation of the extruder is terminated, it is withdrawn by the hydraulic press to suck back the plastic at the tip of the nozzle. This device allows the application of open nozzles. The total amount of sucked back will be reduced, because the gas will cause problems for some plastics.
07 Most of the extruder screw mat materials need to adjust the rotation amount of the screw village during the injection molding cycle time, so that when the extruder screw injection is completed, most of the plastic foam will be left in a small amount, so that the extruder screw can be guaranteed Do a reasonable push time and maintain a fixed sniper pressure. The cushion material of the small injection molding machine is about 2mm; the large and medium-sized plastic machine is 8mm. No matter how much the extruder screw pad material value is applied, it must be maintained and will not change. Today, the size of the extruder screw mat can be controlled within 0.11mm.
08 The rotation rate of the extruder screw The rotation rate of the extruder screw obviously endangers the stable level and efficiency of the entire process of the injection molding process on the plastic. The faster the extruder screw rotates, the higher the temperature. When the extruder screw runs at high speed, the friction (cutting) kinetic energy transmitted to the plastic improves the high melting efficiency, but also increases the unevenness of the melt temperature. degree. Because of the necessity of the surface speed of the extruder screw, the rotation speed of the extruder screw of the large and medium-sized plastic machine should be less than that of the small injection molding machine. The reason is the cutting energy caused by the screw of the large extruder at the same rotation speed. Much higher than the screw of a small extruder. Because the plastics are different, the extruder screw rotates at different speeds.
09 The evaluation of plastic injection needle injection plastic machinery is generally based on the amount of PS that can be injected in each injection molding process, and will be measured according to Gu Si or grams. Another kind of qualifying system software is based on the volume of the melted plastic injection function
10 The evaluation of the melting workability plastic machine is generally based on the amount of PS ash that can be melted uniformly within 1 hour, or the amount of PS heated to the uniform melt temperature (in pounds and kilograms), which is called the melting workability
11 The melting work capacity estimation should be clear whether the production quality can be maintained in all processing processes. A simple formula for the relevant production capacity and melting work capacity can be shared. The following diagram: t = (total injection sniper volume gX3600) ÷ (plastic machine The melting amount kg / hX1000) t is the minimum period. If the period of the grinding tool is less than the t value, the plastic machine cannot melt the plastic sufficiently to achieve a uniform melt viscosity, so injection molding products often have errors. Especially when paying attention to the quality of injection molding for thick walls or high-precision dimensional tolerances, the amount of ash shot and the amount of fusion must match each other.
12 The residence time of the injection cylinder The speed of dissolution of the plastic is due to temperature and time. For example, plastics will dissolve after being at a high temperature for a period of time; but when they are in a natural environment with a relatively low temperature, it takes a long time to dissolve. Therefore, the residence time of the plastic in the shot main cylinder is very critical. The specific residence time can be determined according to the test by measuring the time required by the colored plate plastic according to the injection cylinder, which can be roughly calculated by the following formula: t = (the injection cylinder rated ash amount gX period S) ÷ (Ash shot gX300)