Learn the Key Concepts of CNC Machining & What to Look for in a Machine Shop

Organizations across industries can enhance their manufacturing processes by leveraging computer-numerical control (CNC) machining. The objective of CNC machining is to create a prototype by cutting a block of material into a specific shape. In this post we explore what you should know about CNC machining and the range of CNC machines that are used to manufacture custom parts and components.

The objective of CNC machining is to create a prototype by cutting a block of material into a specific shape. CNC machining boasts both financial and production advantages over manufacturing alternatives like conventional machining and 3D printing. It is more cost-effective, more accurate, and a faster process overall. 

But the appeal of the process doesn’t end there. Rather than relying on live operators to control the manufacturing functions, CNC machining features pre-programmed software and consoles that oversee the movement of the factory tools at play. The process can be deployed to monitor a broad range of machinery—including but not limited to grinders, mills, and routers—through a specific set of prompts.

Developed in the 1940s, the first CNC machines used punched-paper technology instead of the digital software we see today. That said, the process has consistently produced large-scale results with great precision, no matter the application. The computerization component of CNC machining guarantees comprehensive, consistent outcomes.

How Does CNC Machining Work?

CNC machining is common in projects that require a high level of precision and repetition. The process can accommodate 3D shapes that—in many cases—are too complex to create via conventional machining. The instructions are written in G-code, which is generated using a form of CAD or CAM software before being fed to computers.

The code is written and revised by programmers, and as such, it can be updated as needed to produce the correct prototype shape and quantity. Upon activating a CNC machining system, the desired cuts and shapes are programmed into the software and relayed to the machinery that will carry out the tasks. The pre-programmed CNC machines feature the exacting, high-speed movements required to customize the prototype.

When the program is loaded, an operator will conduct a test of the code to make sure it’s error-free. This trial run is called “cutting air,” and is meant to protect the CNC machine by reducing the risk of damage. Even the smallest mistakes involving speed or positioning can scrape the CNC machine.

To this end, while the design details are automated in CNC machining—this helps to ensure consistency throughout the production process—a design may require cutters and drills to meet the exact specifications of the prototype. (We’ll go over this in more detail shortly.) A router or spindle will then turn the cutting implement and cut the material.To this end, while the design details are automated in CNC machining—this helps to ensure consistency throughout the production process—a design may require cutters and drills to meet the exact specifications of the prototype. (We’ll go over this in more detail shortly.) A router or spindle will then turn the cutting implement and cut the material.

As the program runs, the process can be repeated with the highest precision. Here are two things of note in terms of how CNC machining works:

1. The CNC machining process involves open- and closed-loop systems.

   There are two systems used in CNC machining to manage position control. Open-loop systems run a signal in one direction from the controller to the motor of the machine. Conversely, closed-loop systems are capable of receiving feedback signals, and can therefore correct errors regarding velocity and position.

   This means that with minimal force and speed, the process can run through an open-loop control. With more force and greater speed, closed-loop control is needed to oversee the pace, consistency, and precision of the CNC machine. An open-loop system is best used in small-scale projects, while a closed-loop system is ideal for industrial applications.

2. There are a number of different types of CNC machines

   Using a CNC machine, complicated cuts can be achieved in mere minutes. CNC machining is a popular way to customize prototypes made from a variety of materials, allowing the manufacturer to generate complex shapes that would be challenging or even impossible to create manually.

   Basic machines tend to move in one or two axes, while more advanced machines may have up to five axes. Multi-axis machines can turn and flip the material automatically, eliminating the need for manual intervention. They are usually more accurate as well.

   The different CNC machine types are as follows:

   • Mills - Mills are the most common type of CNC machine. Frequently used in industrial manufacturing, they rely on G-code programs and shape the end prototype by moving across the X, Y, and Z axes.

   • Lathes - Lathes are similar to mills, only the tools operate in a circular motion. Like mills, lathes can produce complex designs that would be impossible to create with a manual machine.

   • Plasma Cutters - Plasma cutters use a plasma torch to cut hard surfaces like metals. The process involves a combination of compressed-gas air and electrical arcs.

   • Water Jet Cutters - Like plasma cutters, water jet cutters shape hard materials like granite and metals—this time through the high-pressure application of water. Water jet cutters offer a cooler alternative for materials that can’t withstand a high-heat process and are often used in the mining and aerospace industries. 

   • Electrical Discharge Machines - Also known as die-sinking or spark machines, electrical discharge machines use electrical sparks to discharge a current and remove pieces of the material to achieve the desired shape.