? ? ? ? In recent years, with the development of industry 4.0, China's manufacturing industry is developing from "manufacturing" to "intelligent manufacturing". 3D printing technology has been widely used in China's manufacturing industry. 3D printer can provide efficient and low-cost support for mold design and manufacturing. Even with the rapid development of 3D printing technology, in some fields, it has gradually begun to subvert mold technology, forming a direct competitive relationship with it.

? ? ? ??"Compared with 3D printing technology, traditional mold manufacturing requires more steps and processes, and the mold production cycle is longer. When mold manufacturers launch a new product, the new product needs to pass strict international standards and certification before it goes to market, and the certification of many parts will take a lot of time. This will put new products in a very disadvantageous position in terms of time to seize the market. 3D printing injection mold is an efficient solution. This is what the well-known manufacturer e-mold does, using 3D printing technology to make injection molds in their open laboratories. " According to Luo Baihui, general secretary of the International Mould Association, it usually takes several weeks to two months to produce a mold. However, 3D printing technology can complete the prototype of the mold in a few hours and modify it immediately according to the test results. Then the final product samples of Zui are produced by injection molding. These product samples can be directly sent for certification, while the traditional mold manufacturing may still be in production, and even before the mold Zui is determined, the 3D printed product has passed the certification, greatly shortening the development cycle. Only in the mold production cycle, 3D printing technology has a certain impact on the traditional mold manufacturing.

? ? ? ??However, experts in the industry said that although 3D printing technology has many advantages, such as short production cycle, convenient raw materials and even product pressure, 3D printing technology can not completely replace the traditional mold manufacturing method, because there are still some problems in the production process of 3D printing technology. For example, 3D printing technology is to process the products layer by layer, which will shorten the production cycle of the mold, but it will also lead to the stepped effect on the surface of the mold. There are similar problems with direct printing molds, which require machining or sandblasting to remove these fine, toothed edges. In addition, holes less than 1 mm must be drilled, larger holes need to be reamed or drilled, and thread features need to be tapped or milled. These secondary processing greatly weakens the speed advantage of 3D printing mold. At the same time, in order to ensure good material flow performance, the injection mold needs to be heated to a very high temperature. Aluminum and steel molds usually experience temperatures of 500F (260 ℃) or higher, especially when processing high-temperature plastics such as PEEK and Pei materials. It is easy to produce thousands of parts with metal mold, and it can also be used as a transition die before Zui's final mass production mold comes out. The mold materials made by 3D printing technology are generally photosensitive or thermosetting resins, which are cured by ultraviolet light or laser. Although these plastic molds are relatively hard, they are damaged rapidly under the thermal cycling conditions of injection molding. In fact, in mild environments, 3D printing molds often fail within 100 uses, such as high-temperature plastics such as polyethylene and or styrene. For glass filled polycarbonate and high temperature resistant plastics, even a few parts can be produced.

? ? ? ??In addition, one of the main reasons for using 3D printing molds is its low cost. The cost of production level machining dies is generally $20000 or more, which means that the cost is comparable to that of $1000 printing dies. However, this analogy is not fair. The evaluation of the printed die copy usually only considers material consumption, and does not consider labor, assembly and installation, spraying system and hardware. Protolabsd's aluminum mold, for example, costs $1500 to produce. If more parts need to be produced and 3D printing dies are used, each 50-100 products need to be re printed and the assembly machine is required to test the new mold. On the other hand, regardless of the plastics used, aluminum molds usually remain in good service after producing 10000 parts. Therefore, in terms of production cost, 3D printing is not more cost-effective than traditional mold manufacturing methods.

? ? ? ??In addition, in product design, the principle and practice of traditional injection mold manufacturing has a history of more than a century, and the industry has studied it thoroughly. For example, the draft angle must be greater than or equal to 5 degrees to meet the requirements of most aluminum molds. However, the injection molding of plastic parts with 3D printing mold is facing challenges, and extra care is needed for the number and installation position of ejector pins in plastic mold. In terms of increasing cavity wall thickness and reducing pressure, 3D printing mold (especially high injection temperature) is more flexible to some extent. The design of gates is also different, and tunnel and point gates should be avoided. Direct gate, fan gate and wing gate should be increased to 3 times of normal size. The flow direction of polymer in the printing mold should be consistent with the 3D printing line to avoid high filling caused by viscosity and low pressure. The cooling system can improve the life of the die to a certain extent, but it will not significantly reduce the cycle times of the printing die, because the heat dissipation capacity of 3D printing mold is not as good as that of aluminum mold or steel mold.

? ? ? ??To sum up, 3D printing technology will not completely replace the traditional mold manufacturing industry. Compared with traditional mold manufacturing, 3D printing mold still has some deficiencies in product quality, product cost and mold design. Moreover, 3D printing is not suitable for mass production. The cost unit price of producing 1 piece is close to that of producing 10000 pieces, and 3D printing takes a long time. The current 3D printing technology can only be applied to