3D printing, also known as additive manufacturing, is a technology based on digital model files that accumulates materials layer by layer to form a 3D entity. It has a profound impact on the traditional process flow, production line, factory mode and industrial chain combination and is a An emerging technology that is rapidly evolving in the field, known as 'manufacturing technology of industrial revolution', 3D printing is now widely used in school education, product design, healthcare, aerospace and more.
At present, a new round of scientific and technological revolution and industrial revolution are sprouting all over the world. All countries in the world take additive manufacturing as a new growth point for future industrial development, and promote additive manufacturing technology, information network technology, new material technology and new design concept Accelerate the integration of global manufacturing and consumption patterns began to reshape, Additive manufacturing industry will usher in tremendous opportunities for development.Compared with developed countries, China's additive manufacturing industry, there are still lagging behind the key technologies, lack of innovation capacity, high-end equipment and spare parts Quality reliability needs to be improved, the breadth of application needs further improvement and other issues.
At present, our country attaches great importance to the additive manufacturing industry, as the "Made in China 2025." In order to implement the "Made in China 2025" to promote rapid and sustainable development of China's additive manufacturing industry, accelerate the development of new momentum in the manufacturing industry, In November 2017, the 12 ministries and commissions of the People's Republic of China jointly formulated the "Action Plan for the Development of Additive Manufacturing Industry (2017-2020)". The first of the basic principles and key tasks in the plan is to strengthen innovation and enhance innovation capability.
At present, the principle of 3D printing forming mainly includes FDM / SLS / SLA three types, 3D printing is mainly composed of printers and materials, the printer is the auxiliary forming tool, the material is the key.Material and performance constraints, is the impact 3D printing is an important factor in the development of the current situation is the development of 3D printing materials.The following introduces the PLA material used in FDM printing molding, PLA material is currently very popular material, but also the most used FDM printing material, accounting for To more than 70%.
PLA (polylactic acid), the Chinese name of polylactic acid, also known as polylactide, plant (such as corn, sugar cane) starch as the main raw material synthesis of semi-crystalline thermoplastic aliphatic polyester, ρ about 1.24g / cm3, Tg About 60 ℃, Tm is about 175 ℃, mold forming shrinkage of 0.2% to 0.4%, with biodegradability, the degradation products of CO2 and H2O, the waste will not cause environmental pollution, PLA material life The cycle is shown in Figure 1. The PLA material can be processed by conventional molding methods such as extrusion, blow molding, injection molding and 3D printing. It is widely used in cutlery, packaging, 3D printing and other fields.
Figure 1 PLA life cycle diagram
The reason why PLA materials can be printed by FDM is that the lower the shrinkage rate, the better the dimensional stability of the printed shaped parts, such as no warping and no cracking of the shaped parts; the other is because of its environmental protection , Including synthetic monomer source and biodegradability, so that when printed there is no pungent odor, the waste can also be degraded into environmentally friendly objects; The third is because of its weaker crystallization ability, making the material Matching the cooling setting speed at the printout to the printer's feed rate eliminates the chance of clogging the printer's nozzles.
However, due to the poor toughness of the PLA material, there are a series of problems that occur in the PLA material during printing, for example, the PLA material will be brittle or not after being extruded into a line for 2 months Stable toughness phenomenon, leading to customers in the process of printing line card broken or broken automatically, as shown in Figure 2, severely affected the normal print.
Figure 2 lines automatically broken diagram
Poor toughness of PLA line material is the most common and serious problem on the market, many companies are in the process of modification and optimization in response to this shortcoming, but still no significant improvement. 3D printer technology itself is an innovative manufacturing technology , But if the material is not innovative, it is difficult to meet the different needs of customers, eventually leading to the slow development of 3D printing industry or termination.
Material toughness is poor, the general idea is to directly toughen the modified to improve the impact strength value, which is the traditional modification of universal principle, but after many tests proved that, even if the impact strength of 3D printed PLA material modified by a few Times or even dozens of times, from the modified particles produced into lines, place more than 2 months, still appear brittle or unstable toughness phenomenon.Another more important issue is the addition of a large amount of toughening agent, On the one hand will lead to printed molded parts warpage phenomenon, because the addition of toughening material to improve the shrinkage of the material, on the other hand will affect the material flow, making the printing material temperature had to increase over the PLA The original printing temperature of the material.
Jin 旸 3D R & D team, first of PLA material molecular structure, degradation of a large number of data search and research, combined with the 3D printing and forming must meet the basic conditions, developed a special development program, we develop the program ideas as follows:
First, the choice of toughening agent
1, from the molecular structure considerations: Toughening agent structure should be able to react with the PLA groups containing groups, making the toughening effect is more obvious.
2. Consideration from the principle of biodegradation: As far as possible, the structure of toughener should contain no water-absorbing groups as water will promote the degradation of PLA materials and eventually accelerate the decay rate of the material toughness.
Second, the choice of degradation inhibitor
From the molecular structure of the considerations: adding additives with chain extenders or additives can be terminated PLA functional groups.
Third, lower shrinkage additives choice
1, from the choice of toughening considerations: toughening their contraction rate with the PLA material close.
2, filler considerations: On the one hand, the microscopic shape of the filler is preferably spherical, so that reducing the shrinkage of the modified material at the same time, can achieve the effect of isotropic shrinkage; on the other hand the filler can not be obvious with Promote the crystallization of the role, otherwise the cooling rate is accelerated, it is likely to lead to the material in the printing process to block the nozzle phenomenon.
Fourth, consider the production of standard lines from 3D printing
All additives can not be added too much, otherwise it will affect the stability of the line production line diameter, such as line size tolerance is too large, the final unable to meet the normal feeding of the printer feed.
Fifth, from the appearance of printed molded parts to consider
All auxiliaries, especially fillers, must be added in the proper amount, otherwise the surface accuracy of printed liners will be worsened due to the dispersion of fillers, such as rough surface with obvious particles.
Based on the above ideas, we have developed a special program, after many tests and customer verification, and finally successfully developed a toughness retention PLA material, but also the innovative materials on the market, overcome the 3D printed PLA lines The technical problem of brittleness of the material has really solved the long-standing problem of 3D printing customers. This innovative technology belongs to the world's first.
After the actual verification of the following results: Gold 旸 high toughness retention PLA materials, placed in the air for more than 8 months, it will not appear brittle or unstable toughness phenomenon, this material has a high toughness retention , Good printing effect, but also to solve the problem of difficult to remove the printing support; the same time, it can also be directly replaced by part of the titanium dioxide to add a white material.Because this paragraph material is not added difficult to disperse the titanium dioxide, making printing parts The appearance and accuracy of the ideal, which is favored by customers, an important reason.
Kim Yong PLA material production lines and print molding shown in Figure 3. Shown
Figure 3 PLA print lines and print the figure
Due to the relatively low barriers to entry of FDM-3D materials, many PLA materials manufacturers are pouring into the industry and the homogenization problem is becoming more and more serious. However, there is still a lack of good products that customers really are satisfied with. Is based on the pain point of this industry, starting from customer needs, technological innovation as the core, after a long period of pre-research, argues that conceived ideas of research and development innovation, development of R & D programs, and then after repeated testing and customer verification, the final development Out of the technology leader, fully meet the needs of customers good material.