CNC Router Building considerationsBy Youssef Edward
November 19, 2018
CNC router building is not an impossible task those days. All you need is to maintain a good knowledge for the subject and get sufficient knowledge in program desiging such as Autocad.
The major task for building you CNC is to build the mechanism over which the machine is constructed. The electrical part is not so important to learn since the driver boards are shipped in the market and is ready to use it. The software also is shipped and ready to use and no need arises to build new software. Mach3 is the most common software used to manage CNC.
Many considerations must be considered when going to design the mechanism. The most important one is to reduce momentums in all parts of the machine. For instance, if the z axis holder if made far from the workpiece, it will generate torque that will make the machine vibrate or at least it will not be rigid.
Making your machine steady is the most important issue for your machine. Weakness in some parts will cause the machine vibrate while the the machine running which will cause negative impacts on the finish. This is very important point to consider when building your CNC machine.
The more strength of joining between parts, the better done the building. Welding tends to become stronger then using bolts and nuts. As a rule, everything that can be weld inside the machine, do it by welding. Especially, the body of the machine, or the bed on which all the parts are fixed, must be very rigid. This is the most important part you must pay attention to.
The space between the rails on the y axis must be spaced not too far. As discussed above, more space make momentum that affects the performance of operation. Also the spindle must be too close to the workpiece for the same reason.
If you followed the above guidelines when building your CNC machine, you will get finer results. So what about the hardware electronics you will need. All you will need is the motor drivers and the interface card connecting the drivers to the computer. The motor drivers are the power cards giving power to the motors whether they are stepper or servo motors. They taking signals from the computer through the interface card.
The interface card is the card giving signals to the motors and accepts signal directly from computers thought any port such as the printer port or USB port. USB port is the most preferred option because it is easy to use.
Data is sent from computer in the form of pulses. Each pulse the stepper motor rotates only one step. Each step correspond to a defined distance to move linearly. The software must know that distance to be able to work correctly. For example on 5 mm ball screw, one step pulse will move the gantry 0.0125 mm for 400 steps/revolution.
As mentioned before, the software program design for your CNC router is bought ready and no need arises to buy it. Experienced software developers can build it using software design tools such as Visual Studio.net or Java Technology.
Electronic cards for CNC router is also bought from market and no need arises to build them. Electrical engineers can easily build them using L298 integrated circuit and L297 integrated circuit. Both of those IC are very poplar to build stepper motor driver.
The interface card is also easy to build but can be shipped from the market. When buying it, be sure it is compatible with Mach3. This card takes four signals: the clock, direction, enable, and reset. It is easy to be built by electrical engineers also. The main function is to distribute signals to motor cards.