Process differences between 3D printing and CNC, injection molding, and metal powder injection molding

 

Date：[2024/3/6]
 

3D printing was originally created as a method of rapid prototyping, also known as additive manufacturing, and has now evolved into a true manufacturing process. 3D printers enable engineers and companies to simultaneously produce prototype products and end use products, and they have significant advantages over traditional manufacturing processes. These advantages include achieving mass customization, increasing design freedom, allowing for reduced assembly, and can serve as an economically efficient small-scale production process.
Comparison between CNC machining and 3D printing
Differences in materials
The materials used for 3D printing mainly include liquid resin (SLA), nylon powder (SLS), metal powder (SLM), wire (FDM), etc. Liquid resin, nylon powder, and metal powder occupy the vast majority of the industrial 3D printing market.
The materials used in CNC machining are all sheet metal pieces, and the length, width, height, and wear of the components are measured before cutting corresponding sized sheets for processing. There are more material options for CNC machining than 3D printing. Generally, hardware and plastic sheets can be machined by CNC, and the density of formed parts is better than that of 3D printing.
Differences in parts caused by forming principles
3D printing is the process of cutting a model into N layers/N multiple points, and then stacking them layer by layer/point by point in order, like building blocks. Therefore, 3D printing can effectively process structurally complex parts, such as hollow parts, while CNC is difficult to achieve the processing of hollow parts.
CNC machining is material reduction manufacturing, which uses various high-speed cutting tools to cut the required components according to the programmed cutting path. Therefore, CNC machining can only produce rounded corners with a certain degree of curvature. While CNC machining of outer right angles is not a problem, it is not possible to directly produce inner right angles, which need to be achieved through processes such as wire cutting/electrical discharge. In addition, for curved surfaces, CNC machining is time-consuming, and if the programming and operator experience is insufficient, it is easy to leave obvious patterns on the components. For parts with inner right angles or a large surface area, 3D printing does not pose any machining difficulties.
Some people compare 3D printing to stacking cake powder into a cake, while CNC cuts a large cake into small pieces, which is a more appropriate metaphor.
Differences in operating software
Most 3D printing slicing software is easy to operate, and can be proficiently operated within one or two days under professional guidance. Slicing software is currently optimized very simply and supports automatic generation, which is why 3D printing can be popularized to individual users.
CNC programming software is much more complex and requires professionals to operate it. People with zero basic knowledge usually need to learn it for about six months. Additionally, a CNC operator is needed to operate the CNC machine. Commonly used ones include UG, MASTERCAM, CIMATRON, and domestically produced precision carving. The learning of these software is somewhat challenging.
A component can have many CNC machining schemes, and programming is very complex. However, 3D printing only has a small impact on processing time and consumables due to its placement, which is relatively simple.
Differences in post-processing
There are not many post-processing options for 3D printed components, usually including polishing, sandblasting, deburring, dyeing, and so on. The post-processing options for CNC machining parts are diverse, including polishing, oil spraying, deburring, electroplating, screen printing, transfer printing, metal oxidation, laser engraving, sandblasting, and so on.
CNC machining and 3D printing each have their own advantages and disadvantages. Choosing the appropriate processing technology is more important.
The difference between 3D printing technology and injection molding technology
Plastic injection molding refers to the method of obtaining molded products by stirring completely melted plastic materials with screws at a certain temperature, injecting them into the mold cavity under high pressure, cooling and solidifying them. This process began in the 1920s and has a development history of nearly a century. It is currently a widely used and mature industrial manufacturing technology.
In the plastic manufacturing industry, 3D printing and injection molding are often used to compete, and there are also many opinions that 3D printing is the terminator of injection molding. For manufacturers, one of their concerns is whether their competitiveness is high or low. So, what is the difference between 3D printing technology and injection molding?
Production mode
Injection molding technology, as long as there are injection molds, can produce standardized products at low cost and on a large scale. Therefore, for traditional large-scale manufacturing, injection molding is still the best choice at present.
3D printers, on the other hand, do not require traditional cutting tools, fixtures, machine tools, or any molds, and can directly convert any shape of the computer into a physical model automatically, quickly, directly, and relatively *. Thanks to the unique characteristics of 3D printers that differ greatly from traditional injection molding techniques, the more complex non solid objects, the faster the processing speed, and the more cost-effective the raw materials are. Therefore, they are better at personalization Manufacturing of diversified products.
Manufacturing costs
Due to the wide availability of raw materials for injection molding, its characteristics of large-scale and rapid standardized production are also conducive to reducing the cost of individual products. Therefore, in terms of manufacturing costs, the cost of injection molding is much lower than that of 3D printing technology.
However, for industrial manufacturing, the real cost saving aspect of 3D printing lies in the modification of the prototype, which only requires modifying the CAD model and does not incur any manufacturing costs.
In injection molding, if the prototype is a steel mold, the modification cost will be relatively low, but if aluminum alloy mold making tools are used, the cost will be much higher. This is also why many enterprises or individuals engaged in mold design currently choose 3D printers for mold design printing.
application area 
At present, injection molding technology can achieve mass production of items with consistent shapes, making it very suitable for large-scale standardized product manufacturing.
3D printing only requires the input of 3D images through the control terminal to print raw materials into physical models, and even directly manufacture parts or molds, effectively shortening the product development cycle. At present, 3D printing has been widely applied in fields such as maker, architectural design, and mold model design.
Comparison between 3D printing and injection molding of adhesive sprayed metal
Metal Injection Molding (MIM) is a powerful manufacturing process used for mass production of metal parts. But adhesive jet metal 3D printing provides a striking alternative with its unique advantages.
Adhesive spray metal 3D printing uses an array of nozzles to slice CAD models into a series of two-dimensional data. Based on the two-dimensional graphics obtained from slicing, selectively spray adhesive in a metal powder bed to solidify and shape, and layer by layer to complete the entire blank part. Then, the initial blank parts are pre sintered to obtain a certain strength, and then powder cleaning is carried out* After high-temperature sintering, the binder is removed and the fusion between powder particles is achieved, resulting in high-density and high-strength parts. There are both similarities and differences between the two technologies.
Differences and Similarities between Adhesive Spray Metal 3D Printing and Injection Molding
Firstly, the design constraints of 3D printing are minimal, and the characteristic of manufacturing parts layer by layer gives this technology better design freedom. In principle, it can achieve printing of various complex shaped parts. This also means that several parts can be integrated - several connectors can be replaced by one part, but the functions achieved are the same - thereby reducing the number of parts and shortening assembly time. The design of MIM requires consideration of part demolding, which limits some shapes and makes it impossible to manufacture complex structural parts like 3D printing. However, due to the influence of gravity, friction, and shrinkage, the post sintering process of adhesive jet metal 3D printing is not good at processing large-area thin-walled parts without supporting structures, nor is it good at manufacturing slender tree shaped parts.
Secondly, the molding process is different. The adhesive spray metal 3D printing uses an array of nozzles to selectively spray and solidify the adhesive, while MIM uses mold injection molding. However, the post-treatment process for both is the same, requiring high-temperature sintering. After sintering, the density of 3D printed parts can reach over 98%, which is similar to the MIM process. However, due to the specialized degreasing process required by MIM, it is impossible to make very thick parts.
Thirdly, the manufacturing steps of adhesive jet metal 3D printing are fewer than those of MIM. MIM requires mold opening, while adhesive jet metal 3D printing can directly print parts. Because the processing speed for small batches is significantly better than MIM technology. And once the MIM mold is processed, it is not easy to adjust. So, metal 3D printing can be iterated multiple times without increasing costs.
How to choose between adhesive jet metal 3D printing and MIM?
In most cases, the choice is mainly based on yield. For prototype manufacturing and small batch production, such as tens of thousands of pieces, choosing the former is a good choice. However, MIM is more cost-effective in mass production, for example, MIM technology can be chosen for orders of several hundred thousand or less.
Apart from yield being the decisive factor, there are other reasons.
Due to the limitation of degreasing, MIM cannot make parts that are too large and thick. The quality of MIM parts is generally within the range of 500g, so for large-sized parts, 3D printing technology is preferred.
In addition, complex designs also tend to choose 3D printing, as the geometric shape of MIM parts is limited by demolding.
There are also differences in surface quality between the two processes. The surface smoothness of MIM is slightly higher, with a roughness of approximately 1-2 μ m. The surface roughness of 3D printed metal parts sprayed with adhesive is 3 μ Above. For those with high assembly accuracy requirements, CNC is required for the post processing process, which can be either injection molding or 3D printing.
conclusion
Regardless of the type of 3D printing process, it is a beneficial supplement to traditional manufacturing processes. For some small batch and complex products, the cost of mold opening or other traditional processes is relatively high. In this case, 3D printing may have a more obvious price advantage and manufacturing efficiency. Therefore, in the future, as specific industries deepen their understanding of 3D printing technology, this technology will become a choice on the industry chain. 3D printing is just a manufacturing process.