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Guide: Understanding The CNC Milling Machine

In this guide, you will learn everything you need to start using the CNC Milling like large CNC machine (เครื่อง cnc ขนาด ใหญ่ which is the term in Thai) for instance, one of the four digital fabrication machines in a Fab Lab. With it, you will use different types of materials to work on your projects.

The CNC milling machine is level 3 equipment and requires permission from the Fab Lab team to be used. Read this guide and schedule your Fab Lab orientation.

What Is It

The CNC stands for Computer Numerical Control; in simple terms, it is a machine with a tool at its “tip” in which a computer controls its movements. Laser cutters and 3D printers are also considered CNC machines, and what differentiates these machines is precisely the “tip,” which can melt plastic, drop a laser or have a cutting cutter. The CNC milling machine uses a subtractive method to model the part, sculpting it on a sheet or block of material, and for that, it uses a router or spindle at its tip to carry out the cutting work.

Every CNC milling machine has at least 3 movement axes, a bed to attach the material, and a router or spindle.

The language used to control the CNC milling machine is called G-Code. On a 3-axis milling machine, like the one at Brasília Fab Lab, the code tells the machine to move the tip in the X, Y, and Z direction precisely. This control allows precise cutting operations in different materials (wood, plastics, metals, etc.) and formats.

The Sizes

Like other CNC machines, CNC milling machines can come in different sizes.

Smaller CNC milling machines usually use small tools to handle small details, e.g., circuit boards. The larger ones work with large materials without so many minute details, such as furniture.

The CNC milling machine at Brasília Fab Lab has a cutting area of ​​35x45x15cm. But attention, this is the total area of ​​the table; whenever you put a material to cut in a CNC milling machine, you will leave a margin of 1 or 2 cm in your material to fix the part on the work table.

The Tool: Milling Cutter

As the name implies, the tool used to cut is the cutter, visually very similar to a drill used in drills; the difference is that the cutter has blades that also cut laterally and not only in one direction.

Drill only drills, and the cutter drills and roughs sideways.

The smaller the details on your part, the smaller the cutter used to machine them. A thin cutter is fragile and can remove little material at a time, making the operation exponentially longer. Try to make most operations on your material with the largest possible cutters to optimize the use of the machine and reduce costs.

The Process

The CNC milling machine is undoubtedly the most complicated machine to use in Brasília Fab Lab, but very powerful once mastered. There are several steps in getting your final piece, and to exemplify the visualization, we made the diagram below.

It all starts with your design (2D or 3D), the shape we want to create on the machine. We import this drawing into a CAM (Computer-Aided Manufacturing) program where you will configure the cuts of the drawing. Soon after, we move on to the machine configuration, where we will place and hold the material and position the CNC to start the cut.

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