3D printing technology has been developed for more than thirty years, its industrial application of the global compound annual growth rate of more than 20%, China and even higher. However，because of its relatively small output base, despite the significance of the 3D printing industry is still a small industry. 3D printing industrialization is slow for two main reasons: first is the printing efficiency is low, that is the manufacturing speed is slow; second is the printing material is expensive, which is the manufacturing cost is high. A slow and expensive technology, it is difficult to be applied to the production line, which is why the main users of 3D printing equipment are mostly research institutes, large companies, research and development departments, schools and 3D printing services.
In order to solve the problem of traditional 3D printing is both slow and expensive, 3D printing 2.0 Binder Jetting / 3DP (hereinafter referred to as BJ) process came into being. Compared with 3D printing 1.0, such as PBF, DED and other metal additive manufacturing process is using “point scanning” technology, there are low processing efficiency, several times the cost of traditional manufacturing technology. It is difficult to achieve large-scale industrial applications. However, using the “line scan” technology of 3D printing 2.0 Binder Jetting, is a high-efficiency, high-precision additive manufacturing technology. It follows the traditional powder metallurgy industry material system and sintering process, low cost, high degree of material standardization, not only provide high-efficiency, high-quality, low-cost metal additive manufacturing solutions for industrial sessions, but also can be applied to the production line, for the large-scale application of 3D printing technology has laid a solid foundation. It is expected that 3D printing 2.0 will bring breakthrough sustained growth for the 3D printing industry.
Based on the three-in-one collaborative innovation system of National Research Institute of Science and Technology, post-doctoral workstation and product development team, and the foundation of nearly 30 years of development of additive manufacturing equipment, Longyuan AFS has mastered key technologies related to equipment, materials and processes of binder injection molding technology, and completed the development of series of equipment such as R series for R&D and P series for production. As well as the development of systematic material processes for iron-based materials, non-ferrous metals, high-temperature alloys, refractory metals, ceramic materials, inorganic salts, polymer materials and food materials.
Longyuan AFS R series equipment AFS-J120R and AFS-J380R are R&D type equipment for universities, research institutes and enterprise R&D institutions. This series of equipment can achieve the highest ±0.2mm printing accuracy, 400~800DPI resolution, 2.5L/h printing speed and 55~62% green blank density. The equipment is easy and fast to operate, with flexible replacement of powder material and binder ink, concise structure and easy maintenance, effectively guaranteeing the efficiency of scientific research and repeatability of experiments. With self-developed industrial control software and data processing software, the process parameters are highly open and independently adjustable, which is not only compatible with a wide range of materials, but also suitable for exploratory research and rapid preparation iteration of new materials.
P series equipment is a production type equipment for MIM, mold and tool industries. This series of equipment adopts the latest up-feeding single-cylinder structure, equipped with V+ precise powder dropping system, double-roller composite high-density powder spreading system, nozzle automatic cleaning, built-in air purification system and other devices, easy and fast operation, flexible replacement of powder materials and binder ink, effectively guaranteeing production efficiency. It can achieve ±0.15mm printing accuracy, 400~1200DPI resolution (freely adjustable), maximum 2.5L/h printing speed and 55~62% density of green blank. High-end production equipment AFS-J380L is also equipped with high-precision molding cylinder transfer car, which can realize the rapid transfer and rapid replacement of molding cylinders, saving curing waiting time; the highest printing accuracy can reach ±0.1mm, the highest printing speed can reach 3.6L/h, the relevant technical indicators reach the international advanced level.
In addition, Longyuan AFS has the ability of independent design of binder formulations, which can meet the development needs of customers for customized binders for new materials and new applications. Based on the equipment, a series of BJ special binder formulations have been successfully developed for more than 20 kinds of substrate materials such as iron-based alloys, light metal alloys, organic glass and ceramics. Among them, the degreasing and sintering process for a variety of materials such as SS316L, SS420 and 18Ni300 meet the international material standards of MIM industry. In addition, the company has set up a professional technical service center in China, which can respond to the customer’s needs quickly and on a full-time basis, providing a solid guarantee for the stable operation of the equipment.
BJ metal technology is known as “Additive 2.0” technology because of its high printing efficiency, low material cost, cost-effective equipment, no additional support, suitable for batching, etc. It will form large-scale industrial applications in the automotive, hardware, electronics, tools, molds, cutting tools, medical devices, sports equipment and other industries. It has a broad market space, and the future market scale is more than 100 billion RMB. At the same time, as a direct metal forming technology, the development and application of BJ metal technology is gradually growing into a core technology trend in the field of metal additive manufacturing, showing a strong vitality in the production of batch metal parts. It is believed that the technology will profoundly affect the traditional manufacturing industry, and will change the market pattern of metal additive manufacturing industry in the future.
AFS 3D Printers
https://www.lyafs.com/3d-printing-equipments
Beijing Longyuan AFS Co., Ltd. is a subsidiary of Beijing 3D Printing Technology, Inc. In 1994, it successfully developed China’s first independent intellectual property rights commercial-grade SLS 3D printing equipment. The company focuses on 3D printing equipment and rapid manufacturing services, with nearly 30 years of experience in 3D printing services. Through a collaborative innovation system of research institutes, postdoctoral workstations, and engineering technology centers, it provides solid technical support. Through a series of intelligent equipment, such as SLS selective laser sintering, SLM selective laser melting, 3DP sand mold printing, BJ metal/ceramic printing, DED directed energy deposition, etc., independently developed, it provides users with complex sand mold, sand core, wax mold printing, sand mold printing rapid casting, wax mold printing precision casting, metal finished product rapid manufacturing and other services. More than a thousand equipment and processing service users are distributed in fields such as aviation, automobile, rail transportation, ship pumps and valves, engineering machinery, sculpture, and others.
In December 2022, Longyuan AFS, as a Chinese 3D printing equipment service provider, successfully delivered its self-developed BJ binder jet ceramic printing device AFS-J380 to a leading university in China.
Image: Before the delivery of the BJ binder jet ceramic printing device AFS-J380, which was developed by Longyuan AFS.
Image: At present, the BJ binder jet ceramic printing device AFS-J380 developed by Longyuan AFS is in normal operation in the university.
AFS-J380 is a customized model developed by AFS based on the BJ binder jet metal equipment based on the R&D trial production needs of ceramic materials proposed by this user, which is especially suitable for the development and trial production of ceramic materials.
The equipment adopts high-strength frame structure and the latest up-feeding powder single cylinder structure, equipped with double-roller composite powder spreading structure, high-resolution inkjet printing system, air purification system and high-precision forming cylinder transfer car, which can achieve the highest ±0.2mm printing accuracy, 20-40s/layer printing speed and 37-40% green blank density.
Easy and fast operation, flexible replacement of powder materials and binder ink, effectively guarantee the efficiency of scientific research and repeatability of experiments. With self-developed industrial control software and data processing software, the process parameters are highly open and independently adjustable, which is not only compatible with a wide range of materials, but also suitable for exploratory research and rapid preparation iteration of new materials.
Other research and production BJ binder jet metal printers from Beijing Longyuan AFS. As shown below, （1）Research equipment AFS-J120R, （2）Medium-sized research equipment AFS-J380R,（3）Production equipment AFS-J380P.
sales@lyafs.com
Beijing Longyuan AFS Co., Ltd. is a subsidiary of Beijing 3D Printing Technology, Inc. In 1994, it successfully developed China’s first independent intellectual property rights commercial-grade SLS 3D printing equipment. The company focuses on 3D printing equipment and rapid manufacturing services, with nearly 30 years of experience in 3D printing services. Through a collaborative innovation system of research institutes, postdoctoral workstations, and engineering technology centers, it provides solid technical support. Through a series of intelligent equipment, such as SLS selective laser sintering, SLM selective laser melting, 3DP sand mold printing, BJ metal/ceramic printing, DED directed energy deposition, etc., independently developed, it provides users with complex sand mold, sand core, wax mold printing, sand mold printing rapid casting, wax mold printing precision casting, metal finished product rapid manufacturing and other services. More than a thousand equipment and processing service users are distributed in fields such as aviation, automobile, rail transportation, ship pumps and valves, engineering machinery, sculpture, and others.
According to the data of China Casting Association, the total output of castings in China reached 54.05 million tons in 2021. Among them, automotive castings lead the industry application with a 28.5% share, becoming the largest demand user in the casting field.
As the automotive industry continues to evolve, lightweight design is bringing greater driveability and lower fuel consumption to vehicle manufacturing. More and more automakers are achieving lightweight manufacturing of vehicles through 3D printing technology in their manufacturing process. These include world-renowned automakers such as Porsche, Tesla, BMW, Mercedes-Benz, Volkswagen, Ford, and Honda, all of which are exploring the possibilities that 3D printing can bring to automotive manufacturing in their respective design centers.
In January 2022, Mercedes-Benz released the concept car VISION EQXX, which achieves a lightweight design through 3D printing sand casting of a large integrated rear subframe. The cycle time was four months, and through bionic design, the original 70-plus components were integrated into a single structure with extremely high stiffness and excellent crash performance.
In addition, some smaller components have been optimized through 3D printing. The shock absorber dome, for example, is used to accommodate the suspension components at the front of the car. The weight was reduced by about 4 kg when it was cast in a 3D printed sand mold.
Recently, BMW also released the much-anticipated M4CSL model. The car is a high-performance model based on the M4 Coupe. By adding 3D-printed cylinder heads, it adds 40 hp to the original 503 hp output, enabling it to accelerate to 100 km in just 3.6 seconds, bringing new power to the lightweight of the racing car.
BMW is also using 3D printing technology for exterior trim in some models. In the BMW Individual M850i xDrive Coupe Night Sky Custom Edition, the exterior mirror caps, front air inlet splitter, grille and around the front wing vents are replicated by 3D printing technology with Weidmann patterns. The car’s brake calipers are also 3D printed, allowing for not only a more detailed and complex pattern, but also a 30 percent weight reduction compared to standard components, thus greatly enhancing driving dynamics and ride comfort.
3D printing lightweight design can optimize the energy performance of the car, which is one of the reasons why all major car companies are striving for lightweight body. For new energy vehicles, every 10% reduction in vehicle mass can increase the range by 5%-6%, therefore, lightweighting is one of the important technical paths for new energy vehicles to achieve energy saving, reduce consumption and increase range.
Beijing Longyuan AFS Co., Ltd., a Chinese 3D printing equipment service provider, manufactured an aluminum alloy lightweight frame for a large vehicle manufacturer, which showed an irregular geometry. The design team optimized the frame structure, printed the sand mold and cast it by 3DP inkjet sand printing equipment developed by Beijing Longyuan AFS Co.,Ltd. The final weight of the frame was less than 5KG, the dimensional accuracy reached CT7 level, the surface roughness was less than Ra12.5μm, and the overall manufacturing cycle was only one-fifth of the traditional manufacturing process.
In the future, 3D printing technology may become a more viable solution with the integration of multiple weight reduction strategies, which makes it a powerful guarantee for improved fuel economy. Compared with traditional automotive manufacturing, 3D printing technology can save more costs for car companies and shorten the time to market for product development. In addition, whether using lightweight alloys, high-performance polymers or geometry optimization to achieve weight reduction or save more space, 3D printing has become an indispensable key technology in current automotive trends.
【About Us】
Beijing Longyuan AFS Co.,Ltd. is a subsidiary of 3D Printing Technology, Inc. group, focusing on 3D printing equipment and manufacturing services. Through the self-developed SLS selective laser sintering, SLM selective laser melting, 3DP sand printing, BJ metal printing, DED directed energy deposition and other series of intelligent equipment, we provide users with sand printing rapid casting, wax printing precision casting, finished parts rapid prototyping, gradient metal 3D printing and other rapid manufacturing services in the nationwide manufacturing centers. More than 1,000 equipment and processing service users in the aerospace, automotive, motorcycle, rail transportation, ship pump valve, machinery manufacturing, art casting, metal processing and other fields.
With the rapid development of the national economy, the traditional foundry industry has brought great impact, especially in clean production, intelligent casting has put forward higher requirements, and rapid prototyping sand technology is an effective way to introduce intelligent technology into the foundry industry.
Sand rapid prototyping technology is currently the main three-dimensional inkjet printing (3DP) technology and selective laser sintering (SLS) technology. Among them, sand-based inkjet printing technology has the advantages of high forming efficiency, large forming size, low thermal stress, etc., and is more suitable for large-scale, flexible, rapid and intelligent production.
The origin of 3DP sand-based inkjet printing technology
3DP sand-based inkjet printing technology was invented by Professor Emanuel and others at MIT in the U.S. A patent application was submitted in 1989 and a patent was granted in 1993. The method used in this technology utilizes a nozzle that jets a liquid binder to bond the powder laid on the powder bed into shape.
Schematic diagram of the sand inkjet printing process
The technology works on the principle that the system first lays a layer of powder on the table (the powder is pre-mixed and cured, and the inkjet print head sprays bonding agent (furan resin) on the powder bed according to the shape of the cross-section generated from CAD data to print a cross-section; the working cylinder drops a layer thickness (0.2~0.4mm thickness of the sand type layer); the system keeps repeating the above steps until all cross-sections are printed; finally the cured sand type is removed from the The final cured sand pattern is removed from the working cylinder, and the uncured excess powder is removed to obtain the final sand pattern.
The casting process creates complex sand patterns directly from 3D graphic data, changing the traditional casting method of using molds, making cores, molding, and closing boxes.
The products produced by this technology are highly accurate, and the sand mold and core are quickly formed in one piece, which significantly 3. shortens the product development and production cycle.
The technology has advantages such as flexible modification of model design, which has outstanding effect on improving product precision and reducing sand-iron ratio, especially suitable for the production of complex castings with internal structure.
Significantly improve the casting site environment, reduce the labor intensity of workers; machine for human, labor costs drop significantly; typical digital manufacturing, improve the intelligence level of casting production.
The industrial application of foundry additive manufacturing technology will have transformative significance and far-reaching impact on the transformation and upgrading of the foundry industry, foundry smart manufacturing and the construction of future foundry smart factories.
Beijing Longyuan Automatic Molding System Co., Ltd. (hereinafter referred to as “Longyuan AFS”), a subsidiary of China’s leading 3D printing company Sandi Technology, made an ECU bracket for a diesel car company. This product is a small batch of rapid trial production, from receiving customer drawings to Delivery of the finished part in just 4 days, the casting material is 250 grey iron.
This article describes some of the applications of 3DP sand-based 3D printing technology.
In the aerospace, automotive, marine pump and valve industries, this technology is suitable for the R&D and manufacturing of prototype parts and the production of small and medium batch castings, eliminating the long mold opening time and high mold opening costs. It also eliminates the need for lengthy mold opening times and high mold opening costs. The technology also allows designers to design castings exactly according to the optimal solution, regardless of the shape of the casting, and is no longer limited by machining requirements. Learn more about Beijing Longyuan’s 3DP equipment.
The emergence of 3D printing technology has certain advantages in additive manufacturing. At present, 3DP technology has a wide range of application prospects in the field of sand casting.
First of all, the use of 3DP technology to print sand, instead of manual operation, all the molding process is carried out in a relatively closed box, the printing process will not appear the phenomenon of dust, reducing the emissions to the environment, and significantly improve the labor environment.
Secondly, compared with traditional casting, 3D printing technology omits the link of making molds, improving efficiency and saving production costs.
Third, 3D printing technology can improve product size accuracy and enhance product quality.
Fourth, 3D printing technology provides sufficient flexibility for product design. Since 3D printed sand patterns are not constrained by the size and shape of the product, the parameters can be changed at any time during the production of the product for local or overall correction, enhancing the efficiency of product development and verification.
Applications
Beijing Longyuan Auto Forming System Co., Ltd., a well-known 3D printing manufacturing service provider in China, is a new energy vehicle frame manufactured by a large Chinese car company. It adopts a lightweight design and has a complex structure. , There are many small structures, the weight of the casting is less than 5KG, and the casting material is aluminum alloy. Longyuan AFS uses quartz sand material, prints sand molds through AFS-J1600 equipment, replaces traditional steel molds, and then delivers finished parts after casting. The production cycle of the frame is 1/5 of the traditional steel mold casting time, reducing research and development costs and time.
The product has the characteristics of complex structure and fine structure, and the casting material is aluminum alloy. Longyuan AFS uses quartz sand material, prints sand mold by AFS-J1600 equipment, and then after casting, the finished parts can be delivered. The frame is a small batch trial production, and the production cycle is 60 days to complete 30 pieces of fast cylinder head production, which significantly reduces the R&D cost and time.
The application of 3DP sand printing technology simplifies the molding process, significantly shortens the production cycle, reduces the casting manufacturing cost, effectively improves the efficiency of new product development, and can be widely applied in the field of complex structure, high quality requirements, and single-piece small batch casting manufacturing.
Sand casting is a traditional casting process in which sand is used as the main molding material to make the casting pattern. Sand is generally used for gravity casting, but low-pressure casting and centrifugal casting can also be used when there are special requirements. Sand casting is not only suitable for batch casting of various sizes and complex shapes, but also for metal materials with high melting points, such as copper alloys and ferrous metals.
3DP sand casting has the advantages of short manufacturing cycle, low R&D cost, integrated sand/core manufacturing and the ability to produce any complex shape castings or prototypes without making wooden molds or mold patterns, and can realize overall near-net molding of complex castings.
By using 3DP sand molding method to realize the rapid casting of this product, it has the following outstanding advantages.
3D printing technology directly prints sand blocks according to the model, eliminating the process of mold design and processing, which can shorten the construction period by more than two months.
In the casting development stage, the need to constantly adjust the casting process, mold modification difficulties. 3D printing in the process improvement stage only need to directly modify the sand data, improve the efficiency of process development.
3D printing can print out part of the sand block of traditional parting, simplifying the grouping scheme of the sand block, while ensuring the dimensional accuracy of castings.
The sand pattern prepared by using 3D printing technology has high porosity, which is not only easy to clean, but also has good air permeability, solving the choking fire defect, and can directly print hollow sand core to further improve the exhaust capacity.
With the development of 3DP technology, it is gradually recognized, accepted and applied by more and more enterprises. Beijing Longyuan Automatic Forming System Co., Ltd. (hereinafter referred to as “Longyuan AFS”), a leading 3D printing manufacturer in China, is a motorcycle frame manufactured by a car company. The product has a complex structure, weighs 27KG, and has a thin tube There are many roads and other characteristics, and the casting material is aluminum alloy. Longyuan AFS uses quartz sand material, prints sand molds with AFS-J1600 equipment, and then casts them to deliver finished parts. At present, the supply volume has reached more than 5,000 pieces, and a small and medium-sized trial production scale has been formed.
In the future, more companies, foundries and suppliers will use 3D printing technology to speed up the development and production of new products in their own supply chains, so as to respond more actively to changes in market demand.
Humans began pouring the first sand castings approximately three millennia ago. And until recently, that technology has remained virtually unchanged (see Figure 1):
• A replica, or “pattern,” of the desired object is placed in an open-ended, steel molding box.
• A special type of sand is poured around the pattern, which is pounded firmly into place and then removed.
• A sprue is cut to allow molten metal to flow into the mold, along with a gate that joins the sprue to the mold cavity.
• A core is used to replicate parts having internal features.
• Molten metal is poured into the mold; when the metal cools, the completed part is removed.
That’s sand casting in a nutshell, although journeyman patternmaker Dave Rittmeyer will tell you there’s far more to it than that. Rittmeyer, the customer care and additive manufacturing manager at Hoosier Pattern Inc., Decatur, Ind., also will tell you the industry has undergone a dramatic shift over the past decade or so, thanks in part to AM.
It’s eliminated much of the tedium of the sand casting process while making the process faster, more flexible, and significantly more cost-competitive than other casting methods.
“Lead times with traditional patternmaking processes are best measured in weeks and months,” Rittmeyer said. “3D printing has drastically shortened that, sometimes to just a day or two. In one example, we tooled up for a crane case in three weeks. That normally would have taken us 14 weeks. We’re also able to print very complex molds and cores that would otherwise have been impractical to manufacture.”
Jetting Success
In 1993, researchers at MIT invented a 3D printing process called binder jet. Three years after that the company now known as ExOne Inc. took the binder jet ball and ran with it, changing the sand casting industry forever.
It developed a cold-hardening binder system that deposits sand in layers 0.26 to 0.38 mm thick, then binds selective areas with a liquid polymer that solidifies the sand.
Hoosier was founded in 1997 by three journeyman patternmakers who operated a couple of CNC machines. They bought their first sand printer—an ExOne S-Max—in 2013.
“Today we have more than 25 machining centers and four S-Max sand printers, and roughly half of our business is 3D-printed sand cores and molds,” said Rittmeyer. “I don’t have an exact figure, but we literally print thousands and thousands of each annually.”
The Indiana company also operates a Stratasys Fortus 450mc FDM machine and a 3ntr A2 for building prototypes, low-volume patterns, and various tooling for around the shop.
3D printing has transformed the company from a regional pattern shop to a global one. Hoosier Pattern now ships 3D-printed sand products “all over the world,” said Rittmeyer.
Higher volumes and relatively simple tooling are still produced using traditional manufacturing methods—milling, turning, and EDM—while everything else is sent to one of the company’s 3D printers. But the balance is steadily shifting to printing.
Said Rittmeyer, “For one piece, or even a hundred pieces, the [printer] usually is the way to go—although we do have one print job that calls for 2,200 parts a year, and just this morning the customer called to see if we can double that.”
Made in Montrose
Craft Pattern and Mold Inc., Montrose, Minn., is enjoying similar additive success. The company had been buying 3D-printed molds from Hoosier Pattern but, about a year ago, decided to invest in its own system.
“There were several reasons for it,” said company President Tony Cremers. “Hoosier was doing a great job for us, but when you’re spending a certain amount each month on outside services, at some point it makes more sense to bring that work in-house.
“The other part is lead time. No matter how good the supplier, having your own printing capabilities determines how quickly you can respond to your customer.”
Craft Pattern started 35 years ago as a production pattern shop. It slowly expanded into prototyping and product development work then began pouring small quantities of parts. It has since added 4- and 5-axis machining services, plastic injection molding, and other capabilities.
Adding sand printing made sense. Adopting the technology, however, required Craft Pattern to learn some things about the technology.
For instance, the surface finish on a 3D-printed mold generally is not as good as one made from a pattern, said the shop’s general manager, Steve Shade. “We’ve also had to adjust our workflow and rethink some of our design practices. 3D printing affords us the ability to ignore some of the basic principles of sand casting, allowing for draft, parting, and coring configurations that simply aren’t feasible using traditional tooling.
“Our designers are no longer bound by the rules they’ve been trained to follow and worked with their entire career, which completely changes how we approach a project.”
Because of this, and other factors such as not having to physically build tooling, the timeline for delivering a cast metal part is drastically reduced.
He noted, though, that the “real elephant in the room is cost.” Whether it’s made of metal, plastic, or sand, anything that’s 3D-printed is generally going to be more expensive. “So you can’t just say, ‘Let’s print everything,’ because it’s not yet competitive from a total-cost-of-acquisition standpoint.”
With traditional tooling, the cost of patterns and core boxes can be amortized, allowing for a relatively rapid reduction in per-part cost as volumes climb. With 3D printing, on the other hand, the cost per part is fairly fixed according to the volume of printed sand, so the economies of scale do not yet apply.
“Still, if you’re looking for a few pieces tomorrow or have parts with very complex geometries, 3D printing is the answer,” said Shade.
Cremers agreed. “It’s definitely made us much more flexible,” he said, adding that the shop can shift directions quickly, even turning parts around the next day. And “it’s made a huge improvement to our core manufacturing. Where before we might have made five or 10 separate cores and then glued them together, we can now print them all as a single piece. Between the labor savings, the part quality, and just the overall process control, it’s a significant advantage.”
Source：thefabricator
Researchers have identified a technique for 3D printing sand with great strength.
Materials are a key factor in determining the cost of an additive project, particularly if the part being produced is large. Doubling a dimension means the cube of the material is required. This is the game when 3D printing large objects with construction 3D printers.
Currently the de facto standard construction 3D printing process is concrete extrusion. However, there was a time long ago when it was not, and researchers experimented with a variety of techniques.
One in particular I recall was D-Shape. Almost ten years ago this company, founded by Enrico Dini, attempted to build a building-sized sand 3D printer. While the venture never proceeded much further, they did use a binder jet style of solution: a layer of sand would be pushed over an area, and then an arm would pull a toolhead over top to deposit a binder. Repeating this layer-by-layer generated a huge sand object that would have to be dug out of loose sand when complete.
One of the issues with that approach was that the resulting object just wasn’t very strong. Now that problem may have been overcome by researchers at the Oak Ridge National Laboratory. They’ve found ways to dramatically strengthen 3D printed parts made from sand and binder.
This process was developed for use with standard silica sand, found all over the planet.
The process involves using a polyethyleneimine binder. This binder, when used to fuse silica sand, was found to more than double the strength over conventional binders. They explain:
“We report the discovery of a versatile polyethyleneimine (PEI) binder for silica sand that doubled the flexural strength of parts to 6.28 MPa compared with that of the conventional binder, making it stronger than unreinforced concrete (~4.5 MPa) in flexural loading.”
Note this is for unreinforced concrete. Reinforced concrete would obviously be stronger, but so can sand objects made using the new polyethyleneimine binder.
The researchers also found a way to make the sand part even stronger. They explain:
“Furthermore, we demonstrate that PEI in the printed parts can be reacted with ethyl cyanoacrylate through a secondary infiltration, resulting in an increase in flexural strength to 52.7 MPa.”
Demonstration of the strength of 3D printed sand objects using a new binder [Source: Nature]
At first glance you might think this development might change the equation for construction 3D printing. That is, if the cost of binder and infiltration agent are sufficiently low to enable competition with the more popular concrete extrusion approach.
However, that’s unlikely to be the case, because the binder actually dissolves in water! An application of water disrupts the hydrogen bonding on the binder, causing it to degenerate.
So what use is this material, then? Plenty, it seems.
While this new binder shouldn’t be used for construction 3D printing due to the danger of water infiltration and catastrophic collapse, it could instead be used for molding.
Imagine 3D printing a large sand mold with a very complex design. The design is sure to be maintained through the molding process due to the strength of this sand part. Strong materials could be cast in such a mold, and then easily removed through a water wash.
If commercialized, this binder could open up more possibilities for larger-scale sand 3D prints for casting applications.
Via Nature
