Can post-processing completely replace traditional processing?

一, Technical boundary: the "upper limit of capability" and "application gap" of post-processing machine processing
1. Differences in how well materials can be used
"Subtractive manufacturing," which is more flexible when it comes to material qualities, is what makes traditional processing possible. For instance, to cut high-hardness alloys like cobalt chromium molybdenum, you need to use PCD tools or ultrasonic-assisted machining. On the other hand, to make similar materials using additive manufacturing, you need to get rid of internal pore defects through hot isostatic pressing (HIP) and then meet surface accuracy requirements through five-axis CNC milling. Even though this method can make high-performance parts, the powder metallurgy properties of additive manufacturing processes limit the materials that can be used. This makes it hard to directly replace the processing ability of traditional forging methods for large metal billets.
The "dual challenge" of getting the right size and surface quality
The main purpose of post-processing is to fix problems that are built into additive manufacturing. For instance, the blade profile thickness tolerance of 3D-printed parts of aircraft engine turbine discs needs to be fixed from ± 0.3mm to ± 0.05mm through wire cutting and grinding. The surface roughness also needs to be decreased from Ra8-15 μm to Ra0.8-1.6 μm. For optical components that need micrometer-level precision, such laser reflectors, traditional ultra-precision grinding is still the best option. This is because post-processing depends on multiple processes working together, which makes it hard to get rid of all the mistakes that have built up.
3. The "efficiency paradox" of processing complicated structures
Additive manufacturing has a "free manufacturing" feature that makes it easier to work with complicated structures like uneven surfaces and internal flow channels. However, the post-processing stage may make this efficiency less useful. For instance, CNC milling is needed to remove support residues from the 3D-printed aluminium alloy parts of a certain type of satellite bracket. This cuts the weight by 15%, but it also takes 30% longer to process than traditional casting and machining methods. The unit cost of traditional stamping and heat treatment procedures is still lower than that of additive and post-treatment combinations for standardized parts made in large quantities, like connecting rods for cars.
二, Cost Structure: The "Economic Threshold" for Processing with a Post Processing Machine
1. Costs of buying and keeping equipment
The price of post-processing equipment such five-axis linkage CNC machine tools and laser polishing machines can be millions of yuan for one unit. To accomplish closed-loop control, these machines need online detection systems and smart network technologies. For instance, it costs hundreds of thousands of yuan to make a special post processor for the German Hammer C20U five-axis machining centre. The programming cost for regular milling machines is only 1/10 of that. Also, the cost of additive manufacturing powder materials (such titanium alloy powder, which costs roughly 2000 yuan/kg) is substantially greater than that of traditional bar materials. This makes the total cost of post-processing even higher.
2. The length of the process chain and hidden expenses
Post processor processing necessitates the amalgamation of many processes, including additive manufacturing, heat treatment, and surface finishing, leading to an elongated process chain and heightened concealed expenses. For example, to make a cobalt chromium molybdenum alloy femoral condyle for a medical implant, electrolytic polishing is needed to get rid of powder adhesion, and then micro milling is needed to fix the thread root. It takes more than 8 hours to process a single piece, although the standard forging and CNC turning procedure just takes 2 hours. Even if post-processing can make things more individualized, it's still hard to match the "one-time moulding" advantage of traditional methods when making a lot of things.
3. Dependence on skills and the cost of labour
Operators need to be more skilled to do post-processor processing. For instance, you need to know how to convert between the workpiece coordinate system and the machine coordinate system in five-axis CNC programming. On the other hand, the training time for traditional turning and milling machining skills is very quick. Also, fixing defects in additive manufacturing (such filling in pores) needs a mix of drilling, welding, and machining, which makes the skills needed for process workers much higher and costs more for labour.
三, Industrial Ecology: The Uniqueness and Cooperative Development of Conventional Processing
1. The function of "ballast stones" in fundamental industries
Basic industries like cars and electricity still use traditional processing the most. For instance, the method of casting and machining automotive engine cylinder blocks can produce millions of them each year. On the other hand, additive manufacturing is hard to get into the mainstream supply chain because it isn't very efficient. Also, regulating the flow of metal lines during classical forging can greatly increase the fatigue strength of parts. This is still necessary for making the primary load-bearing structural components of airplanes.
2. Putting the "niche market" for post-processing in the right place
The main benefit of post-processing is that it meets the needs of "high complexity, low batch size, and high precision." For example, in aerospace, electrochemical polishing (ECP) needs to be used to remove the internal flow channel of 3D printed fuel nozzles. This is done to lower burrs and flow resistance, which is hard to do with traditional machining for such microchannel architectures. In medicine, micro milling is used to change the threaded roots of tailored implants so that they fit the patient's bone tissue. This is something that standard methods can't do.
3. The pattern of "collaborative evolution" in how technology is integrated
The composite process of "additive+subtractive" will be the main focus of rivalry in the manufacturing industry in the future. For instance, Siemens NX software has made it possible for additive manufacturing pathways and five-axis CNC machining to work together to optimize each other. It does this by using digital twin technology to predict deformation and automatically creating compensation programs to keep machining accuracy under ± 0.01mm. Also, combining heat treatment systems with digital platforms like the Simplified Cloud Zero Code System can make production control loops, which makes the cost difference between post-processing and traditional methods even smaller.