Transparent plastic injection molding process
1. PET molding temperature is high, and the material temperature adjustment range is narrow (260-300 °C), but after melting, the fluidity is good, so the processability is poor, and the anti-ducting device is often added in the nozzle. Mechanical strength and performance are not high after injection, and performance must be improved by stretching and modification.
2, PMMA process characteristics PMMA viscosity, flowability is slightly poor, so high material temperature, high injection pressure injection molding, the injection temperature is greater than the injection pressure, but the injection pressure is improved, which is conducive to improve product shrinkage.
The injection temperature range is wide, the melting temperature is 160 ° C, and the decomposition temperature is 270 ° C, so the material temperature adjustment range is wide and the processability is good. Therefore, improving fluidity can be started from the injection temperature. Poor impact, poor wear resistance, easy to scratch, easy to brittle, it should improve the mold temperature, improve the condensation process, to overcome these defects.
3, PC viscosity is high, the melt temperature is high, the fluidity is poor, so it must be injected at a higher temperature (between 270-320 °C), relatively speaking, the material temperature adjustment range is narrower, and the processability is not as good as PMMA. The injection pressure has little effect on the fluidity, but due to the large viscosity, the injection pressure is still large, and in order to prevent the internal stress, the holding time should be as short as possible. The shrinkage is large and the size is stable, but the internal stress of the product is large and easy to crack. Therefore, it is better to increase the temperature instead of the pressure to improve the fluidity, and to improve the mold temperature and improve the mold structure and post-treatment to reduce the possibility of cracking. When the injection speed is low, the gate is prone to ripples and other defects, the temperature of the nozzle is controlled separately, the mold temperature is high, and the runner and gate resistance are small.
The mold temperature is accurately controlled to prevent warpage. An important factor in deformation is therefore recommended for hot runner molds. The mold temperature should be high, otherwise it will cause poor surface gloss and difficulty in demolding.
It is important that a company has a strong R&D team, and production and production can not be underestimated. Choosing a mold manufacturer with rich experience in similar products is also a top priority. A good mold is equal to a cash cow, and a poor quality mold is equal to a pile of scrap iron. The efficiency of the mold factory production is also critical. I think many companies have experienced the development of new electronic products. Waiting for the exhibition to wait for the market to take the lead in the market, there are a lot of product problems, the assembly feel is not good, there are raw edges, or there are gas lines, etc. In short, Can not be put into production. Therefore, the human and material resources invested in the early stage have depreciated. Watching people's new electronic products sell hot in the market, my heart is in full swing. Therefore, choosing a good mold manufacturer requires a comprehensive assessment. It is necessary to look at the factory and audit the factory to see if the factory exists. How many factory equipment are there? How many technicians are there? What similar products have been made. During the on-site inspection, we can communicate with our divisions and talk about all aspects of the details, so that we can rest assured. I think that only the mold manufacturers who can stand the test on the spot can guarantee the opening of the product mold, make the product quality and ensure the delivery of the finished product.
Make molds should be careful not to focus on product design, neglect mold manufacturing:
Some users often only focus on product development and development when developing products or new products, and neglect communication with mold making units. After the product design plan is initially determined, there are three benefits to contacting the mold manufacturer in advance:
1. It can ensure that the designed product has a good forming process and will not modify the stereotyped design because the part is difficult to process.
2, the mold maker can make design preparation in advance to prevent inconvenience in the rush, affecting the construction period.
3, the production of high-quality molds, only the close cooperation between the supply and demand, in order to finally reduce costs and shorten the cycle.
The deformation caused by the warpage of the generally formed injection molded workpiece is mainly caused by the difference in the direction of the forming shrinkage and the change in the wall thickness. Therefore, increasing the mold temperature, increasing the melt temperature, lowering the injection pressure, improving the flow conditions of the casting system, etc., can reduce the difference in the direction of shrinkage. However, it is difficult to correct only the molding conditions, and it is necessary to change the position and the number of the gates, such as injection from one end when forming a long rod.
Sometimes it is necessary to change the configuration of the cooling water channel; the longer sheet-like parts are more easily deformed, and sometimes the partial design of the part needs to be changed. The reinforcing ribs are provided on the back side of the upper side. The use of auxiliary tool cooling to correct this deformation is mostly Effective. If it cannot be corrected, the mold design must be corrected. Among them, * it is important to pay attention to make the wall thickness of the product consistent. In the case of last resort, the mold must be corrected in the opposite direction by measuring the deformation of the product.
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