Both CNC machining and 3D printing are great for making custom designs, but what is right for your project?
What do CNC and 3D printing have in common? They both let you create custom designs and can make objects that can’t be produced by traditional methods, such as injection molding. They are both very useful for prototyping, but they also have their differences.
CNC Machining
CNC stands for Computer Numerical Control. With the push of a button, you can start CNC milling or cutting your parts. And since each CNC machine is different, there’s more than one way to control it. Some CNC machines will let you use CAD files (computer-aided drawings), while others will let you import your files from a USB drive.
3D Printing
3D printing is another additive manufacturing method, but instead of milling material away, as CNC does, 3D printing creates an object by applying layer-upon-layer of material. 3D printing can create complicated geometries, so it’s great for creating test parts.
Both CNC and 3D printing machines are often used to make prototypes of finished products.
What Is The Difference Between CNC Machining And 3D Printing?
CNC machines a tool in a spindle that rotates about an axis. When the material is pressed against the spinning tool, it removes small bits of it at a time, which creates the part. The resulting product is accurate to within 0.001 inches or less.
3D Printing is a form of additive manufacturing where successive layers of material are laid down and joined to create the desired shape. 3D printing can print in multiple materials by changing printer heads, and offers some services that CNC machines cannot, such as printing in full color or producing highly complex geometries.
The Pros And Cons Of Each Process
Pros Of CNC Machining
• Accuracy: The tolerances are typically +/- 0.002 inches, which makes them good for creating parts that have tight tolerance.
• Post-Processing: Like cutting with a saw, CNC machining leaves an edge that only needs to be smoothed out for cosmetic purposes. 3D printing leaves you with edges that need to be sanded or filed afterward.
• Material Choice: The CNC cutting process isn’t limited to certain materials like fused deposition modeling (FDM), which can leave you with a bad part if your printer fails mid-print. CNC comes in handy if your design is made from polycarbonate, nylon, ABS, PVC, or another type of plastic because it can cut through them all. CNC can also work with wood and metal.
• Surface Finish Options: A CNC machine gives you a better surface finish than 3D printing does because, after being cut by the sharp bite of the mill, edges come out smoothly and with a high-quality finish.
Cons Of CNC Machining
• Time: CNC parts take hours - even days - to be made depending on the size and number of parts that are being cut.
• Effort: It requires a lot of engineering and programming, as well as some knowledge of 3D modeling. You might need more than one machine to carve out certain designs.
Pros Of 3D Printing
• Speed: 3D printers are faster than CNC machines because they work by laying down material in layers instead of removing it. It takes a few hours to finish printing, compared to days or weeks for machining.
• Low Cost: The process of 3D printing is less expensive overall because it only requires material, not human labor. And for small-run quantities, FDM 3D printers are cheap enough that you can buy one outright instead of renting time on one at an hourly rate.
Cons Of 3D Printing
• Size limitations: FDM 3D printers print items up to several inches larger than their build volume and with a slightly rough surface finish, but they are still useful for most projects. If your part has overhangs or unsupported spans over four inches, the 3D print may not support itself. Here, you would have to use FDM printing to quickly prototype your part and then CNC machining to create the final version.
• Complexity: 3D printers don’t work well with anything other than plastic; they can sometimes handle metal, but it takes special equipment and significant time investment for setup and post-processing (metal powders and binding agents). Aluminum is better suited for machining.
• Thickness: parts created by 3D printers are usually 1/8" thick or less; CNC machining can make items as thin as.0003" without breaking. So if you need a very thin wall, 3D printing would be the faster option, but CNC machining would be your best bet for an extremely thin wall.
Conclusion
If you need only one part and want it quickly, 3D printing is the way to go because it is fast and easy once you get all your settings right. But when your project is more complex, CNC machining proves its worth with crisper detail and material diversity.
