CNC Machining is a high-tech precision manufacturing process for latching metal parts and plastic components, using the pre-programmed computer software dictates the movement of complex machineries, from grinders and lathes to mills and routers. The current types of CNC machining (CNC machine programming) are available in a wide variety of processes and can be classified according to a variety of different principles. As a professional CNC machined part manufacturer with more than 10 years of experience, DAJIN can provide a variety of CNC machining services (CNC Turning, CNC Turn-Milling) and involve multiple industries. Let's take a look at four common categories of CNC machining, as well as the CNC machining processes and techniques involved in each category.

1. CNC Machining Types in Terms of Manufacturing Process

(1) General CNC Machining - Manufacturing process in which pre-programmed computer software dictates the movement of factory tools and machinery. 

This kind of CNC machine processing is the same as the traditional general-purpose lathe processing. There are CNC machining methods such as turning, milling, boring, drilling, grinding machines, etc. The machining possibilities of this type of CNC machined are similar to those of general-purpose machine tools. The difference is that it can be used to CNC machine parts and components with complex shapes.

(2) CNC Turning - Manufacturing process in which bars of material are held in a chuck and rotated while a tool is fed to the piece to remove material to create the desired shape.

This type of CNC machining is developed on the basis of general CNC machine processing. CNC Turning refers to the CNC machining (also known as multi-step CNC machining center or CNC boring mill center, customarily referred to as the CNC machining center) with tool magazine (capable of holding more than 10-100 tools) and automatic tool changer installed on a general CNC machine, which makes the CNC machining further develop towards automation and efficiency.

(3) CNC Multiaxis Machining - Manufacturing process that involves tools that move in 4 or more directions and are used to manufacture parts out of metal or other materials by milling away excess material, by water jet cutting or by laser cutting.

Some complex-shaped parts cannot be machined with a three-coordinate CNC lathe, such as the CNC machining of aircraft curved parts and propellers. It requires more than three axis of the combined motion to machine the desired shape. Then there is a multi-axis CNC machining, which is characterized by a large number of axes controlled by the numerical control device and a complicated lathe structure. The number of axis axes usually depends on the machining process requirements of the machined parts.

(4) Retrofitted Types of CNC Machining - Retrofitting refers to machines that were originally constructed using older, pre-CNC technology, but later were updated to handle CNC programming as a way to improve their efficiency and functionality. Many of the newer milling machines today are manufactured specifically with CNC technology in mind and feature unique options like built-in tool changers and safety sensors.

CNC Milling: Mills use rotary cutters to cut a variety of manufacturing materials and rely on CNC commands to dictate the depth, direction and angle of the cut. The precision of a cut is far greater now using CNC technology than when these machines were operated by hand.

CNC Lathe: These machines rapidly rotate the manufacturing material on a spindle. The material is then pressed against a carving or abrading tool while it spins to cut or shape it. Lathes are used primarily for symmetrical objects such as cylinders, cones and spheres.

CNC Grinding: A spinning wheel is used to either grate and abrade materials or mold them into a desired shape. These machines are the easiest to program because they typically don't require the same level of precision as a lathe or mill.

2. CNC Machining Types in Terms of CNC Motion Types

(1) Point-To-Point CNC Machining (Rapid Motion) - The numerical control device can only control the CNC machine to accurately move the component from one position to another, that is, only control the axis value of the end point of the stroke, and do not perform any cutting process during the movement. The speed and route of movement between the two related points depends on productivity. In order to have the highest possible productivity on the basis of accurate positioning, the movement between the two related points is first to move quickly to a new axis, and then to a speed of 1-3 level, so that it slowly approaches the positioning point, guaranteeing its positioning accuracy. It is used to minimize non-productive time during the machining cycle. Common uses for rapid motion include positioning the tool to and from cutting positions, moving to clear clamps and other obstructions, and in general, any non-cutting motion during the program.

(2) Linear CNC machining (Straight Line Motion) - When machining parts, it is necessary to control not only the position between the two related points but also the moving speed and route between the two related points. The route is generally composed of straight segments parallel to each axis. The difference between it and the point-controlled CNC machine is that when the tools of CNC Machine move, it can cut a part in the direction of one coordinate axis (usually cutting along a 45° oblique line, but not along a straight line of any slope). And its auxiliary functions are more than the Rapid Motion, for example, to increase the spindle speed control, cycle feed machining, tool selection and other functions. Straight line motion can be used any time a straight cutting movement is required, including when drilling, turning a straight diameter, face or taper, and when milling straight surfaces.

(3) Contour CNC Machining (Circular Motion) - This type of CNC lathe machining motion can continuously control two or more axes at the same time. The machining not only controls the starting point and the end point, but also controls the speed and position of each point in the whole machining process, so that the CNC machining can process complex shaped turned parts that meet the requirements of the drawings. Its auxiliary functions are also relatively complete. 

3. CNC Machining Types in Terms of CNC Servo Control Systems

(1) CNC Open loop Control System - In open loop control, there is no detection feedback device for CNC machining. The flow of the signal from the numerical control device is one-way, so there is no system stability problem. It is also because of the one-way flow of the signal that it does not test the actual position of the moving parts of the CNC machine, so the machining accuracy of the CNC lathe is not high, and its accuracy mainly depends on the performance of the servo system. The working process is as follows: The input data is distributed by the numerical control device to distribute the command pulse, and the controlled worktable is moved by the servo mechanism (the servo element is often a stepping motor).

(2) CNC Closed loop Control System - Since the accuracy of open loop control can not meet the requirements of precision CNC lathes and large CNC machines, it is necessary to detect its actual working position. To this end, a detection feedback device is added to the open-loop control CNC machining to detect the movement of the CNC lathe during processing. The position of the component is matched to the position required by the numerical control device in order to achieve high machining precision.

(3) CNC System-Hybrid Servo Control System - The characteristics of the open-loop control CNC lathe processing and the closed-loop control CNC lathe processing are selectively concentrated, and a hybrid control scheme can be formed. Large CNC lathe machining requires high feed rates and return speeds, and requires considerable precision. If only full-closed control is used, the CNC lathe drive chain and the workbench are all placed in the control link. The factors are very complicated, although the installation and commissioning are often difficult. In order to avoid these contradictions, a hybrid control method can be adopted.

4. CNC Machining Types in Terms of Numerical Control Devices

(1) NC Machining (Numerical Control Machining) - The functions of input, interpolation, and control of such a numerical control system are realized by devices such as integrated circuits or discrete components. In general, CNC lathes have different control circuits, so the versatility of the system is poor. Because it is composed entirely of hardware, the function and flexibility are also poor. Such machining systems were widely used before the 1970s.

(2) CNC & MNC Machining (Computer Numerical Control or Microcomputer Numerical Control) - Such systems use medium, large-scale and very large-scale integrated circuits to form a CNC device, or a microcomputer and a dedicated integrated chip. The main numerical control functions are almost entirely realized by software. For different CNC lathes, only different software needs to be compiled. It can be implemented, and the hardware is almost universal. Therefore, it is flexible and adaptable, and it is also convenient for mass production. The modular software and hardware improve the quality and reliability of the system. Therefore, modern CNC lathes use CNC devices.

The above are four common classifications of CNC machining types that must be understood when performing CNC lathe machining. Only by understanding the types of CNC machines, we can select a suitable CNC lathe for machining according to the shape requirements of the CNC machined/turned parts.