CNC machining parts vary from system to system, and even the same milling machine or router might have different components. However there are certain elements which are present in most, or all of them all of these CNC machines use computer programs and electronics for superior functionality.
A typical CNC machine cuts and moves in three directions, often called X, Y and Z axes or directions. The Z axis runs up and down, the Y axis moves left to right and the X axis runs from the back to the front. Used together, these allow the machine to create various shapes, and some CNC machines even have five or six axes.
The CNC computer system and controller function together, giving instructions to the motor, relaying to the system which direction to go to and so on. Majority of the designs are digitized and in .dxf or other format. You then use a CAM program together with the CAD or other software provided with the CNC machine.
The CAM software converts your 2D or 3D design into G-code or whatever computer language your CNC machine uses. The computer proceeds to convert the G-Code to signals the machine can read, such as currents and voltages which drive the system.
This sounds complicated, but everything happens quickly and today’s CNC machines are plug and play. These systems have an interface where you control the process and with routers, you start with the design and use other programs to create tool paths for the project.
This is the component of the router which performs the cutting. These spindles are categorized by their power, watts or horsepower. The spindle functions by rotating the cutter at different speeds. A standard spindle cuts wood and plastic anywhere from 8000 to 30000 RPMs (revolutions per minute). A router for metal cutting spins at a range of 2000 to 10000 RPMs.
Some CNC wood routers are capable of cutting metals, but usually it is of the non-ferrous type. Routers that cut metal and other materials that are carbon based move at high speeds. This necessitates the use of a cooling system or coolant to prevent overheating.
Some spindles are run by the CNC controller, and this controller is responsible for the RPMs and other functions related to cutting and shaping materials. Other components may be installed such as a touch probe, tool sensor and automated tool changer.
This component is designed to secure and support the workpiece or the material you’re cutting. Though cutting beds come in different forms, their function is the same.
The T-slot is one of the most popular designs, and a lot of machinists and hobbyists like it because their clamps and bolts keep the workpiece secure. Another popular cutting area design is the vacuum table. The vacuum table is often used on high end designs, and it’s especially effective if your company cuts the same materials daily.
However, vacuum table CNC machines only work with flat pieces like sheet and wood. In comparison, T-slots have greater range and work with a wider range of materials.
There are other design options, but the T-slot and vacuum are the most widely used cutting beds. If you do the same work repeatedly, the vacuum design is ideal, but if it’s versatility, speed and efficiency you’re after, the T-slot is preferable.
Every CNC machine axis uses a linear drive to move the spindles in that direction. A typical linear system comes with a lead screw assembly, a linear bearing system and a motor.
The motor serves as the bridge between the system’s electronics and the mechanics. The motor gets its power from the CNC controller, which results in higher rotational power.
There are two kinds of motors used in CNC routers, servo and stepper motors.
Closed loop models are often found on high end machines, and the controller you use will depend on the motor. Regardless which you use, the motor provides power via rotational motion, which is then turned into linear motion. This is the point when the lead screw assembly comes into play. Together with the linear bearing assembly, the lead screw sets the spindle or gantry on the axis.
CNC machines use different techniques to turn rotational motion into linear, with some superior to others. The most widely used are the rack and pinion assembly, ball screw and nut assembly, and a lead screw and nut assembly. Users have their own preferences when it comes to these assemblies, and even the same assembly may function differently per brand.
CNC machines have different features, but basically they can be divided into three, the program of instructions, the machine tool and the controller unit. We have already discussed the machine tool and the controller, so let’s take a deeper look at the program of instructions.
The instructions guides the machine to perform the action you want, i.e. shape the material a certain way, drill an opening in a specific diameter, turn the material a particular way and so on. These instructions are presented in symbolic or numerical format.
A lot of functions in the CNC machine are automatic, but you can provide instructions manually via the MDI (manual data input) mode. A lot of these machines also have a direct numerical control (DNC) system where the machine is handled by computers. This feature is often used in factories and manufacturing plants to speed up the process.
If you want to know how a CNC machine works, understanding the components is mandatory. Even if you don’t know all the functions of those parts and mechanisms, basic knowledge is going to go far in terms of optimizing performance and troubleshooting.
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