1. Technical Features: Accuracy and Efficiency Work Together
The main benefit of CNC machining is that it strikes a good balance between speed and accuracy. For example, the five-axis linkage CNC machine tool can position itself with an accuracy of ± 0.001mm, and the accuracy of repeated placement is even better. It can reliably work on parts that need very precise tolerances, such medical device implants and aviation engine blades. For instance, a certain supplier of automotive parts was able to get a 99.8% pass rate for important dimensions of engine cylinder blocks by using five-axis machining. On the other hand, additive manufacturing has anisotropy in the direction of microscopic grain growth because of the way material layers stack on top of each other. To fix mechanical performance problems, post-processing methods like heat treatment are needed. Right now, it's hard to get the same level of surface smoothness and dimensional consistency as CNC.
The most important thing about additive manufacturing is that it can mold complex structures all at once. The Raptor 3 engine from SpaceX is a good example of this. It uses metal 3D printing to add pipelines to the engine, which cuts down on the number of parts and makes the process easier. This leads to a 21% boost in thrust over the previous engine. But this benefit is mostly in making small quantities and very complicated core parts. For standardized items like gears and engine cylinder blocks for cars that are made in the hundreds of thousands each year, CNC is still the best way to make them since it is faster and cheaper. Data shows that the cost of CNC machining per piece goes down a lot as the batch size goes up. On the other hand, the material utilization rate of additive manufacturing can be over 95%, but in high-yield situations, the costs of equipment depreciation and energy use are still higher than those of traditional methods.
2. Application scenario: the need for multiple needs that can't be met by one solution
The aerospace industry has a model of division of labor that includes "additive manufacturing core components + CNC machining precision structures." For instance, China Aerospace Science and Technology Corporation uses additive manufacturing to print cabin portions together, which cuts down on the amount of parts. However, items like turbine blades that need to survive high temperatures and pressures still need CNC machining. Additive printing makes it easier to make a certain sort of engine fuel nozzle by turning it into a single complex structure instead of thousands of parts. But the micro-scale flow channels on the nozzle surface need to be changed again using CNC electrochemical machining (ECM) to suit the needs of fuel atomization efficiency.
The medical industry has created a two-way road of "personalized customization + large-scale production." Additive manufacturing can help orthopedic implants like titanium alloy hip prostheses fit perfectly with bone tissue, however the surface bioactive coating needs to be improved for bone integration via CNC micro arc oxidation treatment. A specific company made a 3D-printed dental implant with an internal porous structure that was completed by additive manufacturing. The external threads were machined by CNC machining to make sure the implant is stable right after it is put in. This "additive+subtractive" composite technique is a good example of how CNC and additive manufacturing may work together.
CNC is still the most important part of making cars lighter and keeping costs down. Battery trays for new energy vehicles need to be strong and light at the same time. By CNC machining aluminum alloy extruded profiles, one company was able to cut its material costs and increase its production efficiency compared to additive manufacturing. Additive manufacturing can quickly iterate complex surface designs for sensor housings for self-driving cars, but final mass production still needs to be done on CNC production lines to meet the requirements of a million-level annual output and 0.01mm-level assembly accuracy.
3. Industrial Ecology: Combining Technologies and Rebuilding Ecosystems
The world of manufacturing is coming up with a new way of doing things called "additive manufacturing design driven+CNC process assurance." A company that makes commercial airplanes has worked with equipment suppliers to create a new sort of aluminum alloy that is good for making rockets lighter. Additive manufacturing quickly checks the prototype for topology optimization design, and CNC forging and machining technology is used in the mass production stage to make sure the structure is strong and costs are kept low. This "design validation mass production" closed-loop depends on the fact that CNC is the only way to shape materials and do precise machining.
Increasing the division of labor in the industrial chain encourages technological synergy. An intelligent process library created by a certain company in the field of metal additive manufacturing combines more than 100,000 sets of material characteristics and lets users create the best printing solutions with only one click. Nevertheless, post-processing still depends on CNC polishing, sandblasting, and other methods. A certain type of folding screen mobile phone hinge uses 3D printed titanium alloy parts. The key to increasing the yield rate is CNC's ability to remove printing burrs with great accuracy. This "front-end additive + back-end subtractive" strategy of working together has become the norm in high-end manufacturing.
The foundation is the cohabitation of policy and standard construction technology. The International Organization for Standardization (ISO) has released standards for additive manufacturing technology that cover things like material testing and equipment calibration. However, certification for aerospace, medical, and other fields still needs to be integrated with CNC manufacturing systems. For instance, a specific kind of aircraft engine blade must meet both the requirements for finding defects inside the blade and the standards for roughness on the surface of the blade. This dual certification system makes the two technologies even more complementary.
