What is CNC Machining?
In general, machining is the process of transforming a stock piece of material — e.g. a block of plastic or sheet metal — into a final product through controlled material removal processes. CNC relies on the digital instructions passed on from a computer-aided manufacturing (CAM) or computer-aided design (CAD) file. Interpreting these design instructions, the CNC machine is able to rapidly and precisely perform certain labor-intensive functions. Basic machines are able to move on the x,y, and z axes, whereas more advanced machines can also flip parts over, allowing for a more comprehensive transformation without the need for manual intervention.
What Types of Materials Are Used In A CNC Machine?
CNC machines are capable of working with a wide variety of materials. This is one of their key advantages. Common materials include aluminum, brass, copper, steel, wood, foam, fiberglass, polypropylene, and other plastics.
Advantages of CNC Machining Over Traditional Machining
Once you understand the basics, operating a CNC machine doesn’t require absolute mastery. After you have your design, the CNC machine will do most of the heavy lifting. Compare this to a conventional machining technique, which requires deep technical knowledge and a constant focus. In addition to this, there are many other key benefits. Below are a few of these.
- Precision – As we all know, when it comes to mechanical detail, it’s nearly impossible to compete with the level of precision that machines can deliver. For example, precise detailing by processes like drilling and 3D carving is repeatable and consistent.
- Repeatability – One of the top benefits of CNC machined parts is repeatability. Even when tackling mass production, the help of CNC machines gives you the same level of consistency over and over.
- Around-the-clock Capabilities – One key advantage of CNC machines is that they are machines. Or in other words, they can work 24/7 without breaks and minimal maintenance. This means less downtime and optimal productivity.
- Versatility – Most CNC machines are remarkably versatile. Many secondary operations like lathing, milling, drilling, etc. can be done all from the same machine. Having this versatility allows for seamless transitions between processes, which is something that is not really possible with conventional machining techniques.
- Improved ROI – When you take into consideration all of these advantages, it’s not hard to see how your operational costs can be drastically reduced when using CNC technologies.
Types of CNC Machines
We would like to introduce you to some of the different types of CNC machines commonly used in metalworking. Here are the 5 most common types of CNC Machines used:
- CNC Drilling Machines – When you have a material—aluminum, steel, plastic, etc.—that needs holes made, CNC drilling machines are a great option. Because they can be programmed to drill with almost exact precision over and over again, they are perfect for large-scale jobs.
- CNC Lathes – Lathes are essentially the inverse of drills. Whereas a drill works by spinning the bit and putting it in contact with material, lathes work by spinning the block of material against the bit. As the material turns, the cutting tool shapes it into its desired form. This flexibility, along with the precision of CNC technology, makes it the perfect tool for the manufacturing of spherical and cylindrical shapes, as well as symmetrical objects.
- CNC Milling Machines – Milling machines are one of the most common and conventional types of CNC machines in use today. Using rotary cutters, these devices are capable of shaving, cutting, and removing sections of material. As opposed to manual milling, CNC milling can be programmed to meet exact specifications—depth, angle, direction of cut, etc.
- CNC Grinders – CNC grinding machines use a rotary wheel to abrade the material until it has reached its desired shape. Because CNC grinders are easy to program, oftentimes, metal fabricators will use grinders over lathes for jobs that don’t require a high level of precision.
- CNC Plasma Cutters – With typical plasma cutters, the material is cut using a plasma torch. This process is most typically performed on metal materials, but it can be applied to other surfaces. To reach the heat and speed necessary to cut through metal, CNC plasma cutters use a combination of compressed air and electrical arcs to ensure precise, clean cuts.
CNC Milling Machines Vs. CNC Lathe Machines
Most metal fab shops and CNC machining professionals have both milling and lathe machines. Both CNC machines employ the same principle of subtractive machining — you begin with a block of raw material and then shape that block to your desired from though CNC machine techniques. Although these processes are similar, they do have distinct differences. Understanding these differences can help give you a more in-depth understanding of CNC capabilities, allowing you to maximize equipment capabilities and optimize project efficiency.
Operational Differences
The primary difference between lathes and milling machines is the essential relationship between the workpiece and the tool.
Lathe Machine
With a lathe, the workpiece spins about its axis. The tool stays stationary. This process is sometimes called “turning” and is a common method used to create cylindrical parts. Other common operations performed on a lathe include drilling, threading, boring, and grooving.
Milling Machine
Whereas a lathe rotates the workpiece, a milling machine does the opposite — the tool rotates while the workpiece stays still. By utilizing this type of setup, you are given more flexibility when approaching the workpiece, which allows for more intricate and complex designs.
Application Differences
As you have probably gathered after reading the above descriptions, the most suitable time to use a milling machine is when you need versatility. Not only does the design of the machine allow for more flexibility, but it also offers a wide array of available cutting tools. In short, for intricate parts, a milling machine is used.
Lathe machines, on the other hand, are much more limited in their potential applications. This being said, they are the superior choice for cylindrical parts. Lathes are especially useful when you need the precise and consistent production of cylindrical parts. A CNC lathe machine will be able to handle this.
CNC Machining Techniques
Turning
At its core, turning is probably the first machine operation in history. Along with milling, it probably accounts for the majority of CNC machining operations. The process is as simple as clamping a workpiece onto a rotating plate or mandrel. As the piece spins, a moving slide mounted with a cutting tool is held against it. This action is perfect for removing large quantities of the material rapidly. Within this technique, lathes, drill bits, and other parts can be added to produce desired results — whether it be a smooth surface, concentric shapes, slots, grooves, shoulders, or more.
Miling
The easiest way to understand milling is to look at it as the opposite of turning. Whereas turning involves moving the piece and then holding the cutting tool to it, milling holds the piece stationary and rotates the cutting tool on a spindle. Typically, the workpiece is usually held horizontally in a vise and mounted on a table. Mills are primarily used to remove stock from asymmetrical parts. However, they can be used for drilling holes and bores as well. Mills are the go-to choice for those wanting to make notches, chamfers, channels, profiles, and other precise cuts.
Grinding
Being able to make a metal surface flat is an important component of many custom CNC metal works. The surface grinder is the best and most reliable way to achieve this. A CNC grinder applies the same principles as nearly all grinding. A spinning disk is covered in an abrasive grit, and the piece is mounted on a table that is able to move back and forth while the abrasive wheel spins above. While this process allows for various degrees of coarseness, allowing for different finishes, this process does not work with pieces that have large protrusions coming from the surface.
Solid Sink EDM
Solid sink EDM is most often used to create pressure die casting, but rarely is this process applied to a finished piece. EDM is specifically used to make holes, squares, pockets, and other types of shapes. It can also be used to add texture to a surface or make recessed letters or logos. This process works by combining a conductive electrode, which is cut to the exact shape of the feature, with a dielectric fluid to force metal particles off the surface of the workpiece.
Wire EDM
Despite its modernish name, the wire EDM process has been used in the industry for more than 50 years. When describing this process, todaysmachinintgworld.com gives this apt description: “picture a band saw, but instead of a saw blade there is a thin wire, positioned vertically or at an angle, with which you can cut in any x-y direction. This is wire EDM (electric discharge machining), a process that can cut any electrically conductive material, hard or soft, even carbide or diamond.” This process is often used in scenarios where traditional cutting tools don’t cut it — e.g. circular or semicircular cuts.
Cylindrical Grinding
Cylindrical grinding is essentially a combination of surface grinding and lathe turning. Perhaps the greatest advantage of this process is the ability to make precise and accurate tolerances with workpieces that have very smooth textures and surfaces. In this process, the workpiece is held stationary while the cylindrical grinding wheel rotates against the surface.
Need CNC Machining Help?
Although this may seem like a lot, it does not cover all of the amazing capabilities of CNC machining — don’t worry, we’ll save the rest for another blog. If you are in the Saratoga Springs area and in need of custom CNC work, contact us! From laser cutting to robotic welding to CNC machining, we can handle nearly all of your metal fabrication needs.
