By: Cory Hunter
Whether in large-scale industrial manufacturing, or in the avid hobbyist’s home, the presence of CNC machine robotics has changed the face of production and design. Stated simply, CNC or Computer Numeric Control is a process that involves the use of computers to control machining tools. Certain tools like grinders, routers, lathes and mills, can be controlled in this manner to execute complex or repetitious patterns with ease.
In terms of large-scale manufacturing, CNC machining has brought a level of accuracy, control, and precision previously unattainable at a reasonable cost. In that same vein, because CNC machining reduces the need for technician assistance, and dramatically decreases the footprint of many large volume machines, this further reduces overall production costs.
Outside the realm of large-scale commercial or industrial use, CNC machining has also revolutionized the hobbyist workshop, allowing the production of extremely complex parts without the need for large production facilities. CNC machines can be easily constructed on a DIY (Do It Yourself) basis, allowing for a broad range of customization over working area of axis control. Additionally, the cost of producing a system of this nature is paltry in comparison to the price of custom production of parts, or otherwise investing in a large production infrastructure.
The key to CNC machining is tied to linear actuation, where each axis of the system can be articulated based on the users’ designs. In the simplest cases, stepper motors are utilized to move a gantry across a custom extruded linear rail. This can be achieved through a belt and pinion system, where the actuation is achieved through belt-driven across a working distance. Additionally, a lead screw system can be utilized, wherein the gantry is attached to a rotating screw which traverses across the working distance as the motor spins. Finally, micro and mini electric linear actuators can be used to control protracting arms which offer a similar range of motion as these other alternatives. In each of these cases, the movement and control of the system is dependent on the software of embedded computer systems.
Part of what makes Computer Numeric Control systems so effective is the robust and dynamic programming language which has been built around them. The most widely used numerical control (NC) programming language is known informally as G-code, which essentially lets programmers give a CNC machine instructions on what path to move and how fast to travel. Most commonly, the machine tool is a cutting mechanism which cuts away material to leave a finished product. The control computer program, flashed onto a microcontroller unit or being fed dynamically to a computer control system, controls all features like feed rate, coordination, location and speeds.
The original iteration of G-Code began as a numerical control programming language in an MIT servomechanisms laboratory in the 1950’s. At the time, it was unable to encode logical functions such as loops or conditional operators, and essentially provided a system to extrapolate system locations, coded in longhand by the programmers.
Since then, many implementations of been developed which allow more user control, and a more dynamic programming language. Extensions and variations have been added independently by individual developers, controller manufacturers, and machine tool manufacturers. The most recent implementations of G-code include user defined variables, and essentially a higher-level programming language closer to object-oriented alternatives.
How/Why to Use CNC
A CNC allows you to design the part or parts you need, including even the most complex features, quickly and cheaply. It can be an amazing tool for precisely carving, cutting, drilling or machining a large variety of materials such as metal, plastic, wood, foam, or other composites. Basically, a CNC machine operates like a large plotter, moving a machining tool around X and Y axes of a workspace. At the same time, the head moves up and down along the Z axis as well, providing 3D motion to cut almost any shape.
The first step to producing an object using a CNC machine is to create a 2D or 3D image. This image, created using Computer Assisted Drawing tools, can then be converted into G-code which is read by the CNC computer. Once all adequate tests have been run to ensure that the machining head and material are positioned correctly, the process will be initiated, usually taking only a few minutes. Sawing, grooving and drilling will all be achieved in a single programmed process to make the end product. Generally, this program will either initiate rapid movement of the machine tool, controlled feeding of the head in a line or arc, or a system of modulated movements designed to route and bore material to specific dimensions.
Ultimately, a CNC machine can be an essentially important addition to a commercial or non-commercial workshop setting, cutting the cost and time of part production. CNC machines can also be used with a multitude of machining mechanisms, designed to cut, grind, print or drill. Whether your linear actuator system is achieved utilizing belt drives, lead screws, or micro linear actuators, a well-designed CNC machine can achieve the utmost precision. Furthermore, proper programming and 3D CAD design can bring the power of these industrial systems into the hands of non-commercial users.
Disruptive technologies such as this one offer the opportunity to change the face of machining, and make it possible for small workshops to compete with even the most well-funded competitors. This has likely paved the way for a more decentralized innovation process, bringing with it the potential for the next big garage startup to change the way we interact with technology.