Türkiye

Prof. Dr. Fahrettin Ozturk

Computerized Numerical Control (CNC) machining is used quite intensively for the manufacturing of parts in many sectors. In the development process of universal machines, Numerical Control (NC) machines were developed before switching to CNC machines. The working principle of the first used NC machines was in the form of reading a perforated paper by the machine. The programs were created at the desk and transferred to a strip; these strips were processed by the reader of the machine, allowing the part to be processed. After the manufacturing was finished, a new part was processed by rewinding the strip. With the rapid development of the computer and digital electronics industry, this technology made a place for CNC machines. CNC machines are commanded with the help of an integrated computer, allowing the production process to be faster, more productive, highly repeatable, and with the minimum level of human factors. The name CNC, which is commonly associated with machining benches, actually applies to all machines used in production.

Thanks to the capabilities of CNC machines and Computer Aided Manufacturing (CAM) software, geometries that were previously considered impossible to manufacture are now produced with the simultaneous use of 3, 4, 5 or even more rotary or linear axes. CNC machines contain many sub-technologies to do complex work. Examples of these subsystems are cutting tools, coolants, optical rulers, linear guides, and ball screws.

Various cutting tools are used in machining to achieve low surface roughness. This technology can be seen as the most dominant factor for the quality of bench technology. The dynamic characteristics of the tool/machine interaction (Cutting speed, depth, feed rates, cutting tool geometry) directly affect the machining quality. With the use of developing technology, such as innovative cutting tool materials and coatings, the quality of the cutting process has significantly increased. However, due to a major shift to composite and titanium materials in the aerospace industry, the tool longevity has drastically decreased while the processing times have increased. Special coatings such as aluminium titanium nitride (AlTiN) and titanium aluminium nitride (TiAlN) are being developed to increase tool life. High-feed tools with a high feed rate have been developed in order to remove large amounts of metal in rough operations so that it may reduce the processing time. In addition, lens tool and barrel tool geometries are developed for floor finish and wall finish operations, which has significantly improved the machining time by a factor of 4 to 5.

“High-feed tools with a high feed rate have been developed in order to remove large amounts of metal in rough operations so that it may reduce the processing time.”

High-quality alloys such as titanium and Inconel have superior properties and many applications in the industry. With the further development of machining tools, equipment and software technology, these materials are now shapeable by machining. The buy-to-flight ratio is very high for the aerospace industry. Structural parts carrying high flight loads are usually machined from billet material and assembled into the aircraft structure.The machining rates for these structural parts are very high; for example, a titanium structural support part has a raw material weight of 2460 kg, while after machining, the final weight becomes 140 kg, meaning 2320 kg of valuable material is wasted. Processes with approximately 95 percent stock material removal are very common in the aerospace industry.

With the development of new technology, there have been major developments in the field of additive manufacturing. Additive manufacturing allows parts to be produced close to its net geometry, making the ratio of processed material (waste) with respect to the stock material decrease from 95 percent to 5 percent. With this technology, most of the parts could be manufactured close to net geometry with surface quality that does not require machining. Once additive manufacturing technology is made suitable for mass production, the technological cost and speed advantages in the manufacturing stages will make this technology superior compared to casting and forging technology. It is believed that these developments will bring convenience and transform the machining processes.

It is foreseen that the most important future change in CNC technologies will be digital transformation. State-of-the-art CNC technologies bring along opportunities such as being able to communicate with each other, store and transfer qualified information, most importantly, control them from a single center, and incorporate resource planning, thanks to its electronic control units. With this technology, large real-time data can be obtained from machines about the manufacturing process. Speed and efficiency increase in production can be achieved through providing real-time data such as deterioration, wear and display of error conditions on the cutting edges and by processing and making sense of the big data consisting of the sum of these data. An example is the processing of many critical data such as autonomous quality control, predictive maintenance, and tool life prediction in production. Thanks to a cloud system or central data storage systems, data can be exported and instant reports can be accessed. When combined with technologies that play a key role in the manufacturing sector of the future, such as artificial intelligence and machine learning, it is estimated that the development of CNC technologies will go beyond what is thought. Today, where digital transformation and smart production are the focus of the business world, the change in CNC technologies is of great importance. With such innovative approaches, it is inevitable to reduce cost, increase quality, and improve business processes.