What Is The CNC Machining Process?

Computerised numerical control (CNC) machining has become essential in many manufacturing industries. CNC machining is a process that uses computerised controls to operate machine tools. Traditionally machines would have been operated manually by machinists. However as the need to produce parts quicker together with higher accuracy and repeatability, computer controlled manufacturing has now become the defacto standard across the manufacturing industry. Understanding CNC machining is key to utilising this process to create the needed parts. When running a manufacturing plant or working in product development, it?s crucial to understand the capabilities and limitations of CNC machining clearly. This article will explain what CNC machining is, the basics, and how it can be used to create parts. What Is CNC Machining? CNC machining is a manufacturing process that uses computerised controls to operate machine tools. This process can be used to create a variety of parts with a high degree of accuracy, parts are produced rapidly and repeatability. CNC refers to the fact that computers control the process. In CNC milling, a part is created through the process of removing material from a solid block using specific cutting tools. This process can also be referred to as subtractive manufacturing. Types of CNC machines include but are not limited to ? lathes, mills, routers, and grinders. The CNC machining process can be used to create parts from various materials, including metals, plastics, and composites. The type of material and part geometry will determine the specific machining techniques that are used. How Does CNC Machining Work? CNC machining is a versatile process that can create parts of various shapes and sizes. The process can also be used to create parts with complex geometries. In the CNC system, programmes can be programmed on or off-line. Online programming can be done at the machine where the operator uses specific codes and functions to instruct the machine on how to operate and move. Offline programming is usually reserved for more complex parts where highly detailed toolpaths are written known as CAM. We?ll explain in further detail later about how CAM is used to generate G-code (the language the machine needs to operate). Even relatively low-end machines can hold a tolerance of 0.005mm. This level of accuracy is possible because the computer controls the cutting tools with a high degree of precision. More advanced machines will often hold even tighter tolerances, it?s not unusual for machines doing very high tolerance work to be housed in temperature-controlled environments as fluctuations in temperatures can cause minute changes through expansion and contraction of both the part and the machine. The CNC machining process can be used to create parts with various finishes. The type of finish applied to a part will depend on the application?s specific requirements. CNC Machining Programming As mentioned, CNC machining programming is the process of creating a program that will control the CNC machine. The program is created using computer-aided manufacturing (CAM) software. CAM software requires there to be a digital file to work off, this file will be a 3d model of the part being manufactured. CAM software is used to create toolpaths, specifically developed for the specific part. The parts geometry, material and available tooling will have an impact on what tools are selected within the programming process. Different tooling strategies are employed depending on what the person programming wishes to achieve. Depending on the complexity of the component, CAM can take a long time to do well. Feeds and speeds of machine operation are written into the toolpath which will have a large impact on run time, surface finish and tool life. The CAM software is also used to create the code that will be used to control the CNC machine. This code is known as G-code. The G-code is language that the machine controller can understand. G-code contains each and every maneuver instruction, it contains information about axis movements, travel speeds, spindle speeds, tool changes and when ancillary systems should turn on and off to name a few. Often lines of instruction can run into the millions, hence why only a computer can process such vast amounts of data at such incredible speeds. Machining systems can be broken down into other subcategories. Open/Closed-Loop Machining Systems An open-loop machining system is a type of CNC system that does not use feedback to control the cutting process. In an open-loop system, the computer controls the cutting tools based on the information inputted into the system. On the other hand, a closed-loop machining system is a CNC system that uses feedback to control the cutting process. In a closed-loop system, the computer controls the cutting tools based on the information input into the system and feedback from sensors on the machine. Fully Automated CNC Machining Systems A fully automated CNC machining system is a CNC system capable of running without the need for an operator. In a fully automated system, the computer controls all aspects of the machining process. This includes loading and unloading the workpiece and changing the cutting tools when necessary. Types Of CNC Machining There are various types of CNC machining centres. The type of machine that is used will depend on the specific application. Below are the most common types of CNC machining centres. CNC Mills ? Mills use rotational cutting tools to remove material material from stock which will be mounted to a flat bed, usually held in vise or fixture. 3 axis machines are the most common however 4 and 5 axis are often used in production settings. Lathes ? or CNC Turning is based on a rotating workpiece held in place while the cutting tool moves across it. It is aimed at achieving a circular shape. Moreover, the lathe consists of two axes: the X and Z-axis. More advanced machines have Y axis and sub-spindles. The machine moves at a high velocity to get a smooth finish on the workpiece. The lathes can be programmed using the G-code or a unique proprietary code. These languages produce complex designs that would not be possible with manual machining. Plasma Cutters ? This machine uses a plasma torch to cut through flat workpieces and are often used in sheet-metal fabrication .The plasma cutter can cut through various materials, including metals, plastics, and glass. The plasma cutter consists of two axes: the X and Y-axis. Electrical Discharge Machines (EDM) ? This type of machining is used to erode material from the workpiece using. The EDM machine consists of three axes: the X, Y, and Z-axis. Additionally, the machine is programmed using G-code or a unique proprietary code designed by the manufacturing team. These languages produce complex designs that would not be possible with manual machining. Water Jet Cutters ? This machine uses a high-pressure stream of water to cut through workpieces. The waterjet cutter can cut through hard materials, including metals, granites, and glass. It is often used as a cooler alternative for materials that can?t stand the heat generated by other types of machining processes. Conclusion CNC machining is an essential part of the manufacturing process. It has become the cornerstone of manufacturing. CNC machines are now highly developed tools that are able to produce parts with incredible accuracy. They are able to process parts at a speed and repeatability which could never be achieved by a human hand. The chances are, if you look around the room you?re sitting in right now, most of the objects that you see will have been made in a factory, they only exist today because of CNC Machines. CNC machines will have been used to make the moulds, dies and forms that were used to create the parts you see. CNC machines have changed the landscape of the modern world and we are lucky they exist. Contact us today if you?re looking for a partner to help you with your CNC machining needs. We?ll be happy to discuss your project with you and provide a quote. Our team of experts is ready to help you take your project from concept to reality.

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