4 Difference between CNC Router and 3D Printer According to Their Working Principles

4 Difference between CNC Router and 3D Printer According to Their Working Principles

The working principle of CNC router machine
CNC is the abbreviation of Computer Numerical Control. It refers to computer-controlled machining equipment. This technology enables the use of computers to transfer machining data to the equipment to achieve high-precision operations such as milling, turning, grinding, and drilling. This type of machine has a wide variety of functions. Commonly there are CNC machining centers, CNC electric discharge machines, CNC engraving machines, and their control systems are capable of handling programs with control codes or other symbolic instructions, which works by decoding, so that the machine performs the specified actions, and make the workpiece into semi-finished or finished parts by cutting tools.

The engraving machine generally has 2-5 axes; the most common is the 3-axis CNC engraving machine, which is mainly composed of frame, motor, transmission mechanical part, spindle motor, and control system. The basic working principle is: control system translates, processes data, and then changes into electric signal to drive the motor. Motor drive transmission mechanical parts, so that the tool or workpiece on the spindle can move in the X, Y, Z direction, and the high-speed rotation cnc cutting tool cuts off the needless parts of the workpiece. The 3-axis engraving machine is generally used for drilling, milling and cutting of block materials. The cutting tool can be a conventional alloy turning tool or a laser. It can be said that the traditional CNC technology is a subtractive technology. The finished product is obtained by subtracting the needless parts.

The working principle of 3-D printer
If the traditional CNC technology is a ‘subtraction’ technique, then the 3D printer uses an ‘addition’ technique. 3D printing technology originated at the end of the 19th century, and various fast prototyping equipment developed later were extremely expensive. Until recently, CNC technology became an open resource, and the period of fast prototyping patent is near end, so cheap 3D printers will continue to emerge.
The 3D printer is a fast prototyping device, and the basic principle can be seen as a combination of traditional CNC machine and printer. Using CNC technology to convert the model file into the spatial displacement of the rack, the 3D printing nozzle can construct the object by layer-by-layer printing of the powdery metal or plastic bondable material. When printing by an inkjet printer, digital files are sent to the printer. After the printer interprets, a layer of ink is sprayed onto the surface of the paper to form a two-dimensional image. In 3D printing, the software completes a series of digital slices through computer-aided design (CAD) and transfers the information from the slices to a 3D printer. The 3D printer stacks successive thin layers to form a solid object. The biggest difference between a 3D printer and a conventional printer is that the 'ink' uses real and raw material.

There are three common working principles of 3D printer:
(1) "Inkjet" mode: The 3D printing nozzle ejects a very thin layer of liquid plastic material, which can be cured by ultraviolet or laser light, and then the tray is lowered by a very small distance for the next layer to be stacked. This is continuously stacked until the scheduled task is completed.
(2) "Melting and backlog molding" method, no additional curing process is required, the plastic is directly melted in the nozzle, the plastic is extruded, deposited and stacked, and cooled and formed in the air.
(3) "Powder sintering" method, the powder particles are sprayed on the tray to form a very thin powder layer, and then the liquid binder is sprayed for curing, or the powder layer is melted, sintered and cured by laser or electron flow. One layer is stacked step by step. When printing in these ways, if the printed object contains a complicated structure such as a hole and a cantilever, a gel or other substance needs to be added during the printing process to provide support or to occupy a space, and the space needs to be cleared after the printing is completed. There are a variety of media to be printed, including plastics, metals, ceramics, rubbers, foods, and even human cells.

The comparison between CNC router and 3-D printer:
From the comparison of the above working principles, we can see that each has its own advantages and disadvantages.
(1) The CNC router machine can be processed in fixed-structure material or semi-finished products. The processed materials are easy to obtain and cheap. They can be made of metal, wood, stone, plastic, etc., and can be made into quite large sizes, while 3D printers require special printing consumables, which are expensive to print and are not easy to make large sizes.
(2)CNC router machine is suitable for industrial production, mold manufacturing, handicraft production, advertising industry, etc. While 3D printers are limited by materials, the products made are relatively fragile. For example, ‘melting and backlog molding’ machines’ consumables are mainly plastic. The products cannot be as hard as metal. They are generally used for complex toy making, unique craft production, restoration of ancient fossils, etc.
(3)The engraving machine needs to prepare suitable profiles or semi-finished products at work, but 3D printing does not need it. It is very popular among designers that want to make a unique design.
(4)From the structural point of view, there are not many differences. They are all applied to the frame structure consisting of three axes of X, Y and Z. The main difference is that the spindle and the tool used by CNC router machine are used for milling the material, and the 3D printer uses the nozzle to carry out the accumulation of material.

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