What type of CNC machining is right for my project?
CNC machining enables manufacturers to create high-precision parts of consistent quality from virtually any material, including metal, plastic, composites, foam, and even wood. Because CNC machining is highly automated, it offers manufacturers a cost-effective way to execute custom one-of-a-kind projects and mid-volume production runs.
In this article, we'll walk you through the different types of CNC machining and which types are best for specific parts and applications.
Additive processes such as 3D printing make parts from scratch, while CNC machining is a subtractive process, meaning it creates a finished product by gradually removing material from a solid block called a "blank" or "workpiece." CNC machines are guided by digital design files, which are translated into instructions on how the equipment should cut the workpiece.
Using computers to automate and control machining processes can greatly increase the productivity of manufacturers. Because multiple CNC machines can use the same design files to make the same series of cuts on multiple uniform workpieces, they can create parts faster than humans can.
As a highly reproducible production process, CNC machining has played an important role in manufacturing and has largely contributed to rapid prototyping. Before the advent of perforated tape and computer numerical control technology, parts had to be machined by hand. This will always lead to large errors, especially when machines are used for large-scale manual manufacturing. CNC machining transforms manufacturing by introducing greater efficiencies into the process, enabling rapid prototyping and mass production with uniform quality and speed.
Modern CNC machining is a general-purpose manufacturing process that produces high-precision parts that can be used to make a variety of products in a variety of industries. This includes everything from car chassis and aircraft engines to garden tools and surgical equipment.
Types of CNC machine tools
There are two types of CNC machines: three-axis and multi-axis.
Three-axis machining
Three-axis machining includes CNC milling and CNC turning processes, both of which involve moving the cutting device along three linear axes (the three axes are left to right, back and forth, and up and down) while the workpiece is being cut.
With a CNC milling machine, the workpiece remains stationary while the cutting tool or drill rotates at high speed to remove material, resulting in a high-precision part. These machines are easy to program and operate and can be used to manufacture most parts with simple geometric designs.
However, because cutting tools and drills can only move in three axes, certain designs or areas of the workpiece can be difficult to complete or reach. Rotating the workpiece is often a solution, but multiple rotations of each part during the milling process can quickly add to production costs.
On the other hand, the CNC turning process involves attaching the workpiece to a rotating spindle and using a lathe to shape the part. Lathes can produce parts faster and at a lower cost than CNC mills, especially when used for high-volume production runs, but their main limitation is that they can only be used to make rotationally symmetrical parts. This includes parts such as screws, bowls and chair legs.
Multi-axis machining
The multi-axis CNC machining family includes three processes: indexed 5-axis CNC milling, continuous 5-axis CNC milling, and mill-turn machining with live tools.
Compared to 3-axis machining, multi-axis machining allows greater freedom of movement during milling and turning. In 3-axis machining, either the workpiece or the cutting tool rotates (but not simultaneously), while 5-axis machining allows both to rotate and move along three linear axes. While this can make more complex parts, multi-axis machines are more expensive and require specialized machines and operators.
Indexed 5-axis CNC milling is sometimes referred to as 3+2 CNC milling because during machining, the tool moves in only three linear axes, while the workpiece has two rotational degrees of freedom. The main advantage of 5-axis milling is that workpieces no longer need to be manually repositioned between operations, allowing faster and more accurate creation of workpieces with complex geometries.
Continuous 5-axis CNC mills allow the tool and workpiece to rotate and move simultaneously during each operation. This allows manufacturers to create extremely complex geometries with smooth "organic" surfaces that cannot be replicated with comparable accuracy using other forms of technology. Generally speaking, this is the most expensive form of CNC machining per part.
Milling and turning CNC centers combine elements of CNC lathes with milling cutters. The workpiece is fixed to the spindle, which can either rotate like a lathe or hold the workpiece at a specific angle (similar to the functionality of a 5-axis CNC milling machine). The high productivity combined with the versatility of geometric manufacturing makes this process ideal for parts such as centrifugal compressors and camshafts with relatively loose rotational symmetry.
Versatile and Cost-Effective Manufacturing Solutions
While all CNC machining processes allow manufacturers to create consistently accurate parts using a variety of materials, the number of axes differing from machine to machine can help make certain types of parts. For example, machines that are simply designed can be manufactured quickly and economically using a 3-axis system, while a 5-axis machine can be well positioned to increase speed and accuracy to create geometrically complex parts.
MH-10
