Advantages and Disadvantages of CNC Machining vs. 3D Printing
CNC machining and 3D printing are common processing methods in industrial manufacturing. The two types of machining have different production methods, each with their own characteristics, and both can be of great help to industrial production. CNC machining is subtractive manufacturing, while 3D printing is additive manufacturing. Therefore, before choosing a manufacturing method, you must carefully consider a number of things, including the size of the production, the development history of the product, the working time, and the overall budget.
What is subtractive manufacturing?
Reduced material manufacturing refers to the cnc machining production process, through the reduction of materials to achieve the purpose of processing, the most common reduced material manufacturing methods for computer numerical control processing (CNC machining). The history of subtractive manufacturing can be traced back to the 1940s. Engineer John T. Parsons developed the first numerical control machine in order to achieve high complexity, high repeatability, and high precision production design.
The process of subtractive manufacturing involves the gradual removal of raw materials such as metal, plastic, and wood through cutting, drilling, and grinding to complete the process. Although these processes can be accomplished by human labor, manual processing, measuring, and cutting will inevitably lead to errors. And production time costs, labor costs are higher, so in industrial manufacturing, most rely on CNC processing for production. Other common ways of material reduction are laser cutting, waterjet cutting, electrical discharge machining, plasma cutting, and these methods are mostly used in flat surface machining.
In CNC machining, the production process is numerically controlled by a computer, including the use of CAD software to design the product and CAM software to manipulate the CNC machining machine to produce geometric shapes.
CNC machining has been in development for over 80 years, and as technology has changed, CNC machining has been applied to a wide range of applications where raw materials have to be reduced to complete the production process. The last decade has seen the development of many new machining methods in industrial manufacturing, but subtractive manufacturing is still the most common and widely used method.
What is Additive Manufacturing?
Additive manufacturing refers to the process of adding material, usually in layers, to a process. Additive manufacturing was first invented in 1981 by Hideo Kodama of the Nagoya City Industrial Research Institute, and began to develop in the 1980s. It has been in development for more than 40 years now, and the technology has gradually matured, become more reliable, and gradually expanded its use to various fields, including machinery and medical-related manufacturing.
The production process of additive manufacturing is similar to that of subtractive manufacturing. In the case of 3D printing, the first step is to design the product on CAD software, and then export/download the product-related data to STL files for subsequent 3D printing. The third step is to choose the material, common 3D printing materials include ABS, PLA, PETG, nylon, TPU, PVA, HIPS, or other plastic polymers. Then after setting the function and transferring the G-code, you can start 3D printing.
Additive manufacturing includes 3D printing, layered manufacturing, and direct numerical production, and the most common additive manufacturing method is 3D printing, where the 3D printer melts the raw material and deposits it layer by layer until the finished product is completed. The raw materials used in additive manufacturing are still mainly plastic polymers, but in the future there are also opportunities to apply a large number of metal processing.
Uses of Subtractive Material Manufacturing
Subtractive manufacturing can be applied to a wide variety of materials, including metals, plastics and their composites, wood, leather, and so on. Subtractive manufacturing can handle almost any shape, including flat surfaces, holes, cylinders, threads, slots, etc., and can be produced with a tolerance of less than 0.025mm, with a high degree of precision and to achieve a smooth and rounded finished product.
Since subtractive manufacturing utilizes the reduction of raw materials for processing, there is bound to be a waste of materials during processing, and even if the materials can be recycled, they are still waste materials. And compared to additive manufacturing, subtractive manufacturing takes more time to produce parts.
Even with the use of industrial-grade machines, 3D printing technology cannot avoid the phenomenon of uneven product strength and quality at this stage. In contrast, the quality of CNC-machined products is more stable and can withstand more stringent engineering requirements, so most highly precise industries, such as the aerospace industry, still use CNC machining technology to produce manufacturing.
Uses of Additive Manufacturing
The additive manufacturing market is expected to expand to 14.4% by 2026, and the total market is estimated to reach $2 trillion. More and more companies are investing money to accelerate the development of the additive manufacturing industry.
Additive manufacturing in the use of materials, mostly plastic materials, such as PLA, ABS, PETG, nylon, TPE, PC-based, but also carbon fiber, metal, ceramics and other materials for production, but the cost is higher than the plastic material (about part of the introduction of the material see this article). The part of the tolerance is usually below ±0.2mm or ±0.1mm.
Since Additive Manufacturing relies on the superposition of materials, it is effective in reducing the generation of waste compared to Reduced Material Manufacturing. However, since it is made by superposition, it is necessary to go through a polishing procedure to ensure the smoothness of the finished product after it has been shot. Generally speaking, the entire production process is faster than in the case of subtractive manufacturing. Production is highly automated and requires less labor.
Comparison of Characteristics and Uses
The maturity of Additive Manufacturing has made the manufacturing of small parts more productive. In addition to being able to create more complex geometries, it is even possible to achieve some production that injection molding cannot handle. Although additive manufacturing is already a mature technology, and a lot of money has been invested in research and development over the past few decades, there are still limitations at this stage of practice. For example, the types of materials that can be used in additive manufacturing are more limited than those used in subtractive manufacturing, and engineers need to take these limitations into account in their designs to ensure the quality of the finished product. In terms of strength, thermal resistance and smoothness, additive manufacturing cannot achieve the quality of subtractive manufacturing products. In addition, if additive manufacturing is used for metal processing, the cost is much higher than that of subtractive manufacturing.
Even though additive manufacturing can accomplish what only subtractive manufacturing could do in the past, it is generally believed that the status of subtractive manufacturing will not be shaken, and that traditional subtractive manufacturing is able to deal with more mature processing types, and is applicable to the largest variety of materials. Although additive manufacturing is now able to handle metal processing, subtractive manufacturing is a process that retains more of the material‘s properties, and the finished product is tougher than additive manufacturing.
Both are now used in prototyping, with subtractive manufacturing preferred for larger samples and additive manufacturing for smaller parts.
Conclusion
Although subtractive and additive manufacturing overlap in many of their uses, there are differences in the timing and scope of their use. Subtractive manufacturing is better at handling metal processing and producing finished products with smaller tolerances, while additive manufacturing is effective at minimizing material loss and is suitable for producing lightweight plastics.
At present, subtractive manufacturing still has a large scale, and shoulder a variety of production modes. Although additive manufacturing is not a new industry, it still attracts a lot of investment and attention, so there are bound to be more breakthroughs in the future.
