Precision injection molding will be affected by many related factors and environmental conditions, and the most basic are four basic factors of plastic materials, injection molds, injection molding process and injection molding equipment. In the early stage of designing plastic products, engineering plastics with corresponding performance requirements should be selected according to application environment.
Tag: precision injection molding
In terms of injection pressure, ordinary machines: 147-177MPa; precision machines: 216-243MPa; ultra-high pressure machines: 243-392MPa. Reason why precision injection molding machine must be high pressure is: (1) To improve precision and quality of precision products, injection pressure has the most obvious influence on molding shrinkage rate of products. When injection pressure reaches 392MPa, molding shrinkage of product is almost zero. At this time, accuracy of product is only affected by mold control or environment. Experiments show that: after injection pressure is increased from 98MPa to 392MPa, mechanical strength is increased by 3% to 33%.
Modern plastic injection molding machine is a typical system integrating machine, electricity and liquid. Due to characteristics of this equipment, such as molding complex products, less post-processing, and various types of plastics to be processed, it has developed extremely rapidly since its inception. More than 80% of engineering plastic products in the world are processed by injection molding machines.
Precision injection molding refers to an injection molding method in which dimensional repeatability of processed injection molding products is so high that it is difficult to use a general injection molding machine and a conventional injection molding process to meet requirements.
Molding and processing methods of plastic products for household appliances mainly include injection molding, extrusion molding, thermoforming, hollow molding, lamination molding, compression molding, transfer molding, foam molding, casting molding, insert casting, encapsulation, etc. Mainly injection molding.
Product of cyclone filter body is shown in Figure 1. Maximum external dimension of product is 70.78 mm * 37.4 ± 0.25 mm * 47.13 mm, average thickness of plastic part is 2.00 mm, material of plastic part is PC, shrinkage rate is 1.006, and weight of plastic part is 15.86 grams. Technical requirements for plastic parts are that there shall be no defects such as peaks, underfilling, flow lines, pores, warpage deformation, silver lines, cold materials, and spray lines.
Flow divider is a structural part on car controller, which is used to divide flow of liquid. Nowadays, a large number of plastic parts are used in auto parts, which can achieve effects of light weight, low cost, high precision, etc., and properties of plastics bring richer functions to automobiles. It can be said that it is a breakthrough in automobile manufacturing industry. Nowadays, most of plastic machinery parts and components used are injection molding. Structure of modern plastic products is becoming more and more complex, wall thickness of plastic parts is becoming thinner, appearance and precision requirements are getting higher and higher, people's requirements for quality of plastic parts are becoming more and more stringent, technical requirements for injection molding are also getting higher and higher; injection molding industry has entered era of precision injection molding. Precision injection molding means that appearance accuracy of plastic products should meet strict dimensional tolerances, form and position tolerances, surface roughness. Due to high design accuracy of plastic parts, special engineering plastics are used for processing. Conventional injection molding cannot be used for plastic parts, but precision injection molding technology must be used. In order to ensure performance, quality and reliability of these precision plastic parts, stability of long-term use, plastic products with high quality, meeting design requirements of plastic parts must be injection molded. Plastic materials, injection molding equipment, mold design, injection molding process and on-site management must be improved .
Basis for determining precision injection molding is precision of plastic injection molding products, that is, dimensional tolerance, shape tolerance and surface roughness of product. There are many relevant conditions for precision injection molding, and the most essential are four basic factors of plastic materials, injection molds, plastic molding process and injection mold making equipment. When designing plastic injection molding products, engineering plastic materials should be selected first, and engineering plastics capable of precision injection molding must use materials with high mechanical properties, dimensional stability, good creep resistance and environmental stress cracking resistance. Secondly, appropriate injection mold making machine should be selected according to selected plastic material, dimensional accuracy of finished product, weight of part, quality requirements and expected mold structure. During processing, factors affecting precision injection molding products mainly come from precision of mold, shrinkage of injection mold making, variation of ambient temperature and humidity of product.
Precision injection molding refers to an injection molding method in which precision is very high, it is difficult to achieve required injection using a general-purpose injection machine and a conventional injection process compared with conventional injection molding. With rapid development of polymer materials, engineering materials occupy a certain position in industrial production. Because of its light weight, resource saving and energy conservation, many industrial product components have been replaced by engineering plastic parts. Precision molded plastics are widely used in industrial products such as instrumentation, electrical and electronic, aerospace, communications, computers, automobiles, video recorders, and watches.
Precision injection molding machines refer to molding machinery suitable for forming precision plastic products. How to measure or judge a precision injection molding machine? Usually precision injection molding machines have two indicators: one is repeated size deviation of product; the other is repeated weight deviation of product. The former is difficult to compare due to size and thickness of product; the latter represents comprehensive level of injection molding machine. Generally, weight error of ordinary injection molding machines is about 1%, and better machine can reach 0.8%. Below 0.5% is a precision machine, less than 0.3% is an ultra-precision machine. As mentioned above, precision injection molding machines require product dimensional accuracy to be generally within 0.01 to 0.001 mm.
Gud Mould 