What is CNC Machining: Working Principles & Characteristics & Processes & Applications

What is CNC Machining: Working Principles & Characteristics & Processes & Applications

What is CNC Machining: Working Principles & Characteristics & Processes & Applications

Oct 13, 2023

What is CNC Machining?
CNC machining, short for computer numerical control machining, is a manufacturing process that removes material from a blank or workpiece using computer control and machine tools. It
can significantly improve machining accuracy, encompassing both machining quality and processing time control and ensure the continuity of machining quality, thereby maintaining the quality of machined parts.
These two main points result in the production of custom parts tailored to specific requirements.


Characteristics of CNC Machining:
1. High automation and exceptional production efficiency. With the exception of workpiece clamping, all machining processes can be accomplished by CNC machine tools. When combined with automated loading and unloading methods, it becomes an integral part of unmanned control factories.

CNC machining reduces labor, improves working conditions, and eliminates processes such as marking, multiple clamping and positioning, and inspections, effectively enhancing production efficiency.

2. Adaptability to different CNC machining objects. When switching to a new machining object, only the tool needs to be replaced, the clamping method for the workpiece needs to be addressed and the programming needs to be reworked, without other complex adjustments, thereby shortening the production preparation cycle.

3. High precision and stable quality. CNC machining achieves dimensional accuracy ranging from 0.005 to 0.01mm, regardless of the complexity of the parts. Since most operations are automated, it improves the dimensional consistency of batch parts. Precision CNC machining also incorporates position detection devices on precision-controlled machine tools, further enhancing accuracy.

Due to it’s overwhelming superiority, various machining processes have emerged to meet market demands. When choosing a machining process, various factors should be considered, including the surface shape of the workpiece, dimensional accuracy, positional accuracy, surface roughness, etc.

Choosing the most suitable machining process can ensure the quality and efficiency of the workpiece with minimal investment, and maximize the generated benefits.

Different CNC Machining Processes and Their Applications:
By selecting the appropriate machining methods based on the material and workpiece requirements, we can find the most suitable way to machine components. Understanding common machining methods and their applicable scope can help us achieve optimal results.

Turning Process:
Turning is a machining process performed on a lathe to shape the workpiece. It involves using cutting tools to remove material and create rotational surfaces. Turning can also be used to produce threaded surfaces, end faces, and eccentric shafts.

Turning precision typically ranges from IT11 to IT6, with surface roughness ranging from 12.5 to 0.8μm. In finishing operations, precision can reach IT6 to IT5, with roughness as low as 0.4 to 0.1μm. Turning offers high productivity, stable cutting processes, and relatively simple tooling.

Applications: Center drilling, drilling, reaming, tapping, external turning, boring, facing, slotting, contour turning, taper turning, knurling, thread cutting.

Milling Process:
Milling is a method of machining that uses rotating multi-edge cutting tools (milling cutters) on a milling machine to process workpieces. The main cutting motion is the rotation of the tool. According to the direction of the main motion speed during milling, which can be the same or opposite to the feed direction of the workpiece, milling can be divided into climb milling and conventional milling.

(1) Climbing Milling
The horizontal component of the milling force is in the same direction as the feed direction of the workpiece. There is usually a gap between the worktable feed screw and the fixed nut, so the cutting force can easily cause the workpiece and the worktable to move forward together, resulting in a sudden increase in feed rate, leading to chatter.

(2) Conventional Milling
Conventional milling can avoid the chatter phenomenon that occurs during climb milling. When conventional milling, the cutting depth gradually increases from zero, so the cutting edge goes through a stage of sliding and squeezing on the hardened surface of the workpiece, which accelerates tool wear.

Applications: milling flat surfaces, milling steps, milling grooves, milling contoured surfaces, milling spiral grooves, milling gears, cutting.

Planing Process:
Planing generally refers to the machining method on a planer that uses the planing tool to make reciprocating linear motion relative to the workpiece to remove excess material.

The precision of planing can generally reach IT8-IT7, with a surface roughness of Ra6.3-1.6μm. The precision planing flatness can reach 0.02/1000, with a surface roughness of 0.8-0.4μm. It has advantages in the machining of large castings.

Applications: planing flat surfaces, planing vertical surfaces, planing step surfaces, planing right-angle grooves, planing inclined surfaces, planing dovetail grooves, planing T-slots, planing V-grooves, planing curved surfaces, planing keyways in holes, planing racks, planing compound surfaces.

Grinding Process:
Grinding is a method of cutting the surface of a workpiece using a high-hardness artificial grinding wheel (grinding wheel) as a tool on a grinding machine. The main motion is the rotation of the grinding wheel.

The precision of grinding can reach IT6-IT4, with a surface roughness of Ra up to 1.25-0.01μm, or even 0.1-0.008μm. Another characteristic of grinding is that it can process hardened metal materials, making it suitable for precision machining and often used as the final machining process. Depending on the function, grinding can also be divided into external cylindrical grinding, internal hole grinding, and surface grinding.

Applications: external cylindrical grinding, internal cylindrical grinding, surface grinding, form grinding, thread grinding, gear grinding.

Drilling Process:
The process of machining various internal holes on a drilling machine is called drilling. It is the most commonly used method for hole machining.

Drilling machining has lower precision, generally IT12~IT11, and the surface roughness is usually Ra5.0~6.3um. After drilling, semi-precision machining and precision machining are often performed using hole enlarging and reaming. Reaming machining has a precision of IT9—IT6 and a surface roughness of Ra1.6—0.4μm.

Application: drilling, hole enlarging, reaming, tapping, countersinking, flat scraping

Boring Process:
Boring machining is a method of enlarging the diameter and improving the quality of existing holes using a boring machine, with the rotation of the boring tool as the main motion.

Boring machining has higher precision, generally IT9—IT7, and a surface roughness of Ra6.3—0.8mm, but the production efficiency of boring machining is low.

Application: machining high-precision holes, precision machining of multiple holes

CNC machining can be used on various materials, including metals, plastics, wood, glass, foam, and composites. It is widely utilized across industries, with aerospace being a notable sector that employs CNC machining for both large-scale operations and precise fabrication of parts.

Main Industries of Application:
Components manufactured by CNC machining have high precision, so they are mainly used in the following industries:

Aerospace requires components with high precision and repeatability, including turbine blades in engines, tooling for manufacturing other components, and even combustion chambers used in rocket engines.

Automotive and Machinery Manufacturing
The automotive industry requires the manufacture of high-precision molds for casting parts (such as engine mounts) or machining high-tolerance components (such as pistons). Gantry machines can cast clay modules for use in the design phase of automobiles.

Defense Industry:
The defense industry uses high-precision components with strict tolerance requirements, including missile components and gun barrels. All machining parts in the defense industry can benefit from the precision and speed of CNC machines.

Medical implant devices are usually designed to fit the shape of human organs and must be made of advanced alloys. Since no manual machines can generate such shapes, CNC machines are essential.

The energy industry covers all engineering fields, from steam turbines to cutting-edge technologies such as nuclear fusion. Steam turbines require high-precision turbine blades to maintain balance, and the shape of plasma suppression cavities in nuclear fusion is very complex and requires advanced materials manufacturing with the support of CNC machines.

The above is all about cnc machining, I hope to help you. If you would like to know more about cnc, please contact us sales@janeemachining.com.

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