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What Does CNC Machine Stand For? CNC stands for computer numerical control but that's the tip of the iceberg

What Does CNC Machine Stand For?

Whether it is woodworking, metal working or plastic molding, CNC machines are frequently used. These machines are also standard in the aerospace industry to manufacture parts, computer components and in the automotive industry as well. In short they’re everywhere precision is needed, but what does CNC machine stand for?

CNC Definition

CNC stands for computer numerical control. CNC software programs are used by operators to monitor, control and otherwise perform the machine’s actions. A lot of machines can be subjected to CNC, and even older equipment can be upgraded so it’s compatible with CNC. These include sheet metal stamping machines, waterjet cutters, laser cutters, grinders, welders, routers and lathes.

An onboard controller is designated as the computer for industrial machines. For hobbyist machines and retrofitted equipment, a PC will do. Regardless, a CNC controller works with drive components and motors to control and move machine axes and execute commands. In more advanced machines, a feedback mechanism is in place to adjust the cutting position and movement.

CNC Axis

CNC machines possess numerous axes for moving, either rotary or linear, and a lot of systems have both. Waterjets and cutout machines have the X and Y linear axes, while milling machines have X, Y and Z axes. More advanced milling machines come with rotary axes.

A milling machine classified as having five axes have 2 rotary axes and 3 linear axes. This gives the cutting tool 180 degree movement, similar to what laser cutters have. CNC machines with robotic arms are sometimes equipped with six axes.

  • The term 2 axis is used if the cutting occurs in one plane. In this instance, the cutting tool cannot move in the vertical (Z) plane. Usually the Y and X axes interpolate at the same time to produce circular arcs and angled lines.
  • A 2.5 axis is one where the cutting occurs in planes that are parallel to the main plane. However this does not mean they’re at the same depth or height. In these situations the cutter moves in the Z plane but not at the same time as the movements in the X and Y planes. The only exception to this is a cutter moves in Z and makes circles in X and Y.

It is also possible for two axes to interpolate at the same time, but not three of them. With these cutters it’s possible to create 3D objects either by slicing the YZ or XZ planes.

  • A 3 axis system is required for cutters that need the X, Y and Z axes to be controlled at the same time, and this is often the case with free form surfaces. A 4 axis meanwhile, comes with the standard 3 axes and one rotary axis. A 4 axis can be 4th axis position or interpolation.
  • A 5 axis system includes the three axes and a couple of rotary axes. Like the four axis machine, 5 axis systems come in different forms and configurations.

CNC Data Interpretation

CNC controls can only read lines and arcs, and other forms that have to be used must be turned into something they understand. 3D surfaces and NURBS are among those that need conversion, and with desktop CNCs you may have to convert circular arcs as well.

Splines can be separated into various arcs, line segments or a combination of the two. The more line segments converted, the finer the approximation and the less faceted, and the opposite is true with fewer segments.

Desktop CNC

Desktop CNC machines fall under the same definition, except they are smaller and designed for hobbyists and model creation. Desktop CNC systems are lighter and cheaper, and they’re not as accurate as their industrial counterparts, but these are good enough for machining wax, foam and plastic.

Desktop CNC machines operate in different ways. The simplest CNC works like a printer, while other machines have proprietary CAM software and their own command system. There are also CNC machines – desktop or otherwise – which work with G codes, while the more sophisticated ones have specialized controllers.

CAM

CAM Computer Aided Manufacturing or Machining) involves the use of software programs to create codes and tool paths to operate the CNC machine. CAM systems are derived from CAD (computer aided design), and the two are often used in CNC.

CAM systems do not technically operate a CNC machine, but they do make the codes that enable the machine to run. CAM operators have to be versed in its language to run the program. The operators must also create strategies for machining and know what tools to use and when. CAM systems can be very sophisticated especially when it’s used for manufacturing. However there are simpler systems which beginners can learn.

NC Codes

NC is a basic computer language for CNC machines. They are easy to understand and execute, and were developed so programmers can issue instructions minus a CAM system.

NC codes tell the machine what moves to execute and control various aspects such as the coolant and feed speed. There are many types of NC codes, and the most common is G or ISO code. This program was created back in the 1970s and is still used today.

What is the Post Processor?

G codes are widely used, but manufacturers often modify the codes to suit their particular needs, and most develop their own programming languages, so their G code won’t work with another.

For this to work, the CAM program’s paths have to be converted into a form the CNC machine can read. The software used for this is called the postprocessor. Once the postprocessor is properly set up, it produces the right code for the CNC machine. Some CAM systems have postprocessors or something that must be purchased separately.

Conclusion

The information above is an overview explaining what CNC machines are. Obviously they can do a lot more, but this guide shows you how it works and why it is prevalent in manufacturing. By understanding what CNC machines are, you’ll realize their value and importance in various industries.

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