Introduction
In the world of digital fabrication, CNC (Computer Numerical Control) machines stand out as powerful tools capable of transforming raw materials into intricate and precise parts. These machines are commonly used in manufacturing, prototyping, and even hobbyist projects. However, the accessibility of CNC machines has often been limited by the need for specialized manufacturing equipment and technical expertise. This is where my journey began: with a vision to create a CNC machine that anyone could build, using readily available off-the-shelf parts and easily orderable laser-cut parts from SendCutSend.
Design Philosophy
The design philosophy behind this CNC project was guided by a few fundamental principles:
- Simplicity: The design needed to be straightforward enough for anyone to assemble, regardless of their experience level. This meant minimizing the number of unique parts and ensuring that all components were easy to source.
- Cost: While building a machine such as this is never cheap, I wanted to minimize cost as much as possible while maximizing functionality
- Capability & Precision: Despite the focus on simplicity and accessibility, I still wanted to create a machine capable of cutting soft metals such as aluminum with a reasonable accuracy
- Ease of use: From building previous CNCs I have learned that some of the most important features are ease of use/quality of life. For example, I learned how much time a touch probe saves compared to zeroing tools manually. Additionally, a full enclosure decreases noise and cleanup as well as enabling safety.
Mechanical Design
Frame and Structure:
The frame is primarily constructed from 0.25” thick mild steel plates, chosen for their excellent strength-to-cost ratio and easy availability through SendCutSend. The frame consists of five pieces: two identical front/rear parts and two identical side parts. This design choice was strategic, as ordering multiple identical parts from SendCutSend reduces costs. The plates are assembled using laser-cut box joints and U-bolts, a method selected to eliminate the need for tapping any parts, thereby reducing both labor and costs.
(Insert pictures of frame and box joints)
Linear Motion:
For linear motion I choose to use 30mm linear guides on the x and y axis and 20mm on the z axis. I choose round linear guides over rails because of their lower cost and greater rigidity. These rails are mounted at two points using U-bolt clamps and are integral to the whole machines structure. The flatness of standard linear rails depends on the surface they are mounted to, whereas the flatness of these linear guides (with the way they are mounted) is simply dependent on how they come from the factory. (Insert picture of linear guide)
For power transmission I choose ball-screws over other methods such as belts or leadscrews. Ball screws have very low backlash and smooth motion. Two important qualities for a CNC mill. Although they are the more expensive option when compared to a lead screw, they have drastically lower backlash. The price of ball screws has also fallen over the last few years because of Chinese manufacturing. I choose to use Nema 23 motors with integrated ball screws to save on complexity. These ball-screws are however harder to source and had to be custom ordered of Alibaba. (Insert picture of ballscrew)
Electronics and Software
In the past, my CNC electronics have been put together as cheaply as possible with zero safety features. This time I decided to do everything the right way. I employed a circuit breaker and contactor for the ac input of controller box. All conductors also have properly crimped wire ferals for added safety. (Insert picture of contactor)
Dc Power:
All items requiring dc power run of a Meanwell lRS-350 24v supply. A custom 3d printed bracket was also designed to make it easier to mount in the enclosure. (Insert picture of dc power)
Motion Control:
For control, I am utilizing the Open-Builds Blackbox. This is an all-in-one controller with 4 integrated stepper drivers capable of 2.5a each which is enough for the smaller Nema 23 motors.
(Insert picture of blackbox)
Assembly and Calibration:
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Conclusion
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