CNC Machining vs. Sheet Metal Fabrication

Two common types of manufacturing are CNC machining and sheet metal fabrication. While they share some characteristics, such as forming raw metal material into finished parts and integration with automation equipment, they have many differences.

Depending on the details of an application, materials used, and the design intent of a component, one or the other may be a clear choice in terms of manufacturability and efficiency. In other cases, there may be advantages and disadvantages to both options for the same component.

Learn more about the differences between CNC machining and sheet metal fabrication, and what goes into determining which choice is the best for your application.

What Is CNC Machining?

CNC, or computer numerical control, machining refers to a number of subtractive manufacturing processes that are performed by automated machinery controlled by a computer system. Some common examples include:

CNC machines are equipped with cutting tools and jigs and programmed with a specialized set of commands to perform the cuts and other motions required to form a part. CNC machines are usually enclosed in metal cabinets that protect the workpiece, workers, and equipment.

First, a digital rendering of the part is made with computer-aided design (CAD) software. Next, the CAD model is translated into a CAM, or computer-aided manufacturing, file that determines the necessary toolpath, angle, and speed parameters to create part features, profiles, contours, and holes. The CAM file data is then converted into CNC instructions, called G-codes, that the machine follows to make each part. The machine will run the same program and make the same motions over and over, for quick cycle times and great precision.

The machining itself is highly automated. Human operators may be needed to load or unload blanks or to push a start button; however, these tasks can also be automated with collaborative robots or other automation equipment.

What Is Sheet Metal Fabrication?

Sheet metal fabrication encompasses a variety of operations performed on flat sheets or strips of metal in varying thicknesses. Some common examples include:

Many fabrication methods can be automated to speed up cycle times and increase precision in creating part features. The use of jigs and other fixtures also helps ensure that sheets and partially formed components are positioned correctly to achieve the desired dimensions and tolerances.

Differences Between CNC Machining & Sheet Metal Fabrication

For many applications, the nature or design intent of a component and the material it’s made from will determine the best manufacturing method. For example, precision fasteners like nuts or screws are usually machined from a solid blank, hollow bowl-shaped parts are usually made from sheet metal with a CNC turning machine, and cabinet panels are usually formed from sheet metal with a press brake or other bending equipment.

In other cases, there may be multiple ways to design a part: one method that uses sheet metal bent into a shape, and another that involves material removal via machining. Both options may accomplish the same goal, such as a handle or shaft that could be machined from a cylinder or rolled from a sheet. In an application like this, the choice between CNC machining and sheet metal fabrication may come down to these factors:

• Part size, complexity, and dimensions. Some part features (e.g., tapped holes, threads) are easier to achieve reliably with material removal processes like CNC machining, while others (e.g., electrical enclosures, brackets) are more readily achieved by forming a flat sheet of metal by cutting, bending, stamping, etc.
• Tolerances. For some designs, it may be easier to hold especially tight tolerances through material removal than attempting to counter sheet metal characteristics like springback or tearing at stress points.
• Cost. The price of labor, time required to make and finish parts, as well as raw materials will factor into the total cost of production per item.
• Material. Depending on the manufacturing method, different types of materials may be used. For some materials, solid blanks or cylinders of the same material may be more or less costly, or have different availability than a sheet of it. A material’s properties may also influence the manufacturing method, such as a metal that is durable when machined into a component, but that would tear or warp if bent or stamped.
• Design intent. How a part will be used, how it fits into an assembly, and the stresses it will experience under normal operating conditions are important design considerations that influence the material chosen, and therefore, manufacturing methods.
• Manufacturability. Just because a part can be manufactured with a certain method doesn’t mean it will be the most durable, efficient, or achieve the required tolerances. The choice of materials and manufacturing methods may come down to how efficiently something can be achieved with the least amount of mistakes or part failure.

Things like lead time, part volume, availability of automation, finishing processes, and other considerations are also important.

CNC Machining Services From Cenflex, Inc.

Cenflex, Inc., is a leading CNC machining manufacturer that relies on advanced, multi-axis CNC equipment. We produce high-quality parts and assemblies with a variety of manufacturing operations and finishing services, and are ISO 9001:2015 certified. For over 30 years, our family-owned company has served these industries:

Contact us today to learn more about our capabilities, or request a quote to receive pricing details.