Development Tendencies for Designing Mold
The current development features of the whole industrial production are plenty of categories, fast updating and drastic market competition. To meet the customers’ urgent requirements for short date delivery, high precision and low cost, the design of mold has the following development tendencies:
1. Mold design has been developed from empirical design to theoretical calculation and computer aid design. CAD, CAM and CAR have been widely applied in mold making, which makes mold structure mold rational, highly improving processing precision of mold, reducing processing cycle of mold design and development time of products.
2. The mold is developed toward high precision large scale or ultra-small scale. 10 years ago, the precision of precise mold was generally 5μm. Now, the precision has reached 2-3μm. Precise mold with 1μm precision will come out. With the requirement for miniature and precision improving, the precision of some molds whose precision below than 1μm requires to develop superfinish and reduce bench working and other manual operations.
3. Multi-function compound mold will be developed further. Multi-color and multi-material plastic forming mold will be developed quickly. The mold can decrease production cycle and assembly cycle of products, which will be developed and applied in different fields.
4. With the development of hot runner technology, the utilization ratio of hot runner mold in plastic mold will be increased gradually. Mold adopting hot runner technology can highly improve productivity and quality of workpieces, significantly saving raw materials, therefore, hot runner technology is developed quickly and has already widely applied in developed countries.
5. The application of mold standard parts is wider and wider. Mold standardization and application of mold standard parts have great influence on manufacturing cycle. The application of mold standard parts not only can decrease manufacturing cycle of mold, but also can improve mold quality and reduce cost. Nevertheless, the application of mold standard parts will be wider and wider. Plastic, stamping mold, centre, ejector sleeve, screw and spring form stand parts with mold.
6. The prospect of rapid mold is very capacious. Nowadays is the age of multi-category small mass production. In the 21st century, the proportion of the mode of production will account for industrial production by more than 75%. On the one hand, products have short service cycle, on the other hand, categories change frequently, requiring that the shorter manufacturing cycle of mold is better. So, developing rapid mold attracts more and more attentions from people. For example, develop various kind of superplastic materials used to make mold. Use epoxy (E), polyester (P), filler metal (M), glass (G) and other reinforces to make simple mold. Use E, P, P-M, E-G, E-G-M and P-G-M to make mold. Main features of these molds are simple manufacturing process, manageable precision, low shrinkage, low price and higher service life. Besides, cement and plastic also can be used to make mold for auto covering parts. Those molds have already been applied in the U.S., Japan and other developed countries while they still need to be improved and the application also should be expanded. Low or medium melting point alloy mold, spray mold, electroformed mold, refined casting mold, stack mold, ceramic plastic sucking mold, epoxy mold, photo mold and other rapid molds will be developed further. Quick-changing mold base and quick-changing terrace mold will be developed gradually. In addition, single minute exchange of mold device and quick testing mold device adopting computer controlling and manipulator operation will be developed and improved.
7. With constant improving and developing of plastic molding, gas injection mold and molds adapting to high pressure injection molding are also developed. The precision of plastic parts is divided into dimensional accuracy, geometric accuracy and appearance accuracy (gloss and hue). To realize the accuracy, high pressure injection molding and injection compression molding will continue to being researched. In injection molding, the largest factor affecting molding precision is molding shrinkage. High pressure injection molding can reduce shrinkage of resin, increasing stability of plastic dimensions. The mold should have good rigidity and high pressure resistance. Particularly, cavity of precision mold should be quenched, sprue having good sealing and mold temperature should be controlled accurately. Gas-assisted molding has already been mature. It can improve inner and outer appearance of plastic parts, having the advantages of low injection pressure, small deformation and convenience for forming products having large difference of wall thickness. Moreover, it can save raw materials and improve productivity of parts, significantly reducing cost. Gas-assisted mold has been already used in China, achieving good results.