What is CNC Milling?

This once specialist hobby has reached new audiences during the lockdown.

CNC (Computer Numerical Control) machining has always been a common manufacturing method in applications such as engines, mobile phones, and in high-precision products such as watchmaking.

However, this once specialist niche is now appealing to newbies and veterans at the hobby and home level.

In this piece, we’ll be exploring what a CNC milling machine is, more specifically CNC Routers, the tech behind them, what they do, and what you can do at home for those interested in getting involved.

CNC Basics

CNC machining is used extensively in manufacturing and works by taking a piece of material, such as wood or metal, and removes pieces from this material to produce a final design, otherwise known as subtractive manufacturing.

Although in manufacturing, these machines are used to create identical products quickly and efficiently, they’re now also a popular choice for home hobbyists into crafting or even those that are looking to start a small-scale business producing unique items at home. The domestication of this type of technology is generally very new and has only been around for the past few years.

The CNC milling process uses a wide range of cutting tools called endmills, which are controlled by a computer programme that reads and translates a design, which has been inputted by the user to follow a specific path to form the finished product.

Popular things to do at home, include wood art, clocks, ornaments, signs,
instruments, furniture, and much more!

How Does a CNC Router Machine Work?

The CNC machining process happens when the machine runs instructions from a design that the user has created in a CAD program – these can be either be 2 or 3D.

Once the completed designs are converted into a language that the machine can understand, known as G-Code. This G-code file is sent to the machine and the production process begins.

The software will know when to prompt the user to change a tool and/or move and flip the material. This can be in many different materials such as wood, plastics, and soft metals, such as aluminum and brass.

CNC Setup

Prior to the machining manufacturing process, the CNC needs to have the collect endmill (cutting tool) fitted and the workpiece secured (chosen material) using clamps, tape, or a vice. The operator will then load the file, set the work start coordinates, and make final safety checks.

These first few steps are crucial in ensuring that the machine can perform the job without the material falling out of place.

Once all these initial steps are completed, the operator can start the program with the machine’s interface, and the manufacture of the design will begin.

CNC Manufacturing

Once the CNC gets moving, it is capable of cutting incredibly strong material very accurately and at speed. As the manufacturing process continues, the tool performing the cutting or engraving will move in sync with all 3 axes where necessary to ensure each part of the design is replicated exactly.

The angles and direction of this process will depend on the specific design, of course, but the principle remains the same no matter the design or material.

CNC Milling Machine Components

A CNC Router is made up of several different components:

Worktable - As the name suggests, this is where the material is secured as it is worked on. This is situated on top of the workbench or on a purpose-built table

Spindle - The spindle is driven by a powerful motor. This is essentially the component that controls the movement of the required cutting tool. In hobby CNC Router machines, off-the-shelf wood trimming routers are used for convenience and simplicity. As we progress into more industrial Router machines, we move to a 3-phase spindle which ranges in power from 800w to 10+Kw.

Drive Types

There are 3 main types of drive for the CNC axis:

1. Screws
2. Rack and pinion
3. Belts

Ball screws are the most precise and expensive, as they are most often used in precise and industrial machining.

Lead screws are cheaper but suffer from backlash and whip on hobby machines. Rack and pinions are used in large surface area machines (think IKEA furniture production).

Belts are the most popular choice for Hobby CNC routers as they are cost-effective, easy to repair, precise and fast!

Machine Tool

The machine tool, as you can imagine, is the part that removes material from the chosen workpiece and will need to be changed depending on the design requirements, for example, this could be a straight cutter, surface tool, ball nose, or another type specific to the job

The specs of each machine tool will vary in diameter, length, teeth, and material. The very reason that CNC making is so versatile, and thus so popular, is the wide variety of cutting tools and the vast design possibilities.

The best part about these machines now accessible for home use is that the software and design packages are free of charge to use and very user-friendly.

It enables anyone to craft something. Even better, you can run them from your home PC or laptop.