3D Printing vs CNC Machining

CNC machines were the reigning champions of the manufacturing industry for the longest time. Their ability to make many components at once while keeping the uniform is unmatched. That is until 3D printing came on the scene. Now, manufacturers have another production alternative.

Although these two processes have nothing in common, they can still give you the same results even if they have two very different approaches to manufacturing. One removes material to reveal the final shape, while the other adds layer after layer to build what you want. Still, both can produce complex products in large quantities, making them direct competitors. 

So, in the battle of 3D printing vs CNC machining, which one comes out on top? Let’s look better at both processes because the answer might surprise you. 

What Are the Core Principles of 3D Printing

As an additive manufacturing method, 3D printing allows building components from the bottom up with very little waste. It doesn’t need special cutting tools or machines, just the printer. Just upload your model and watch as the printer gives it shape.

One difference between CNC and 3D printing is that you only have a selected choice of printing materials. You could only use thermoplastics for a while, but the selection is slowly growing. Today, resin and metal are also in play. So, for greater material selection, most manufacturers offer 3D printing and CNC machining as part of their machining services.

Common 3D Printing Technologies

Because now we have more material options, there are also several ways to print, including:

• Fused deposition modeling: Everyone is familiar with the FDM method. It melts down thermoplastic filaments and builds sturdy components.
• Stereolithography: During the SLA process, a laser cures a resin into a solid material with a surface finish that doesn’t need much post-processing.
• Selective laser sintering: The SLS method makes metal 3D printing possible. It uses a laser to fuse powdered metals or nylon.

What Are the Core Principles of CNC Machining

Unlike the previous process, which adds material, machining does the exact opposite—it removes it. You place a blank block or sheet in the machine, and it cuts pieces off until it produces the final shape. And the material isn’t an issue. CNC machines can cut and shape:

• Wood
• Hard and soft metals
• Composites
• Acrylic
• Carbon fiber
• Fiberglass-reinforced plastics, etc.

CNC Machine Types and Capabilities

There isn’t just one type of CNC machine. It’s remarkable how many different ways exist for removing material from a blank. There are as many machines as CNC processes, but they still work in more or less the same way. The CNC machines you can find on most manufacturing floors include:

• CNC mills are the most versatile of these machines. They can cut flat and 3 dimensional objects from any material. 
• CNC lathes mostly produce cylindrical objects like shafts and valves. Here, the material rotates while the cutting tool is still.
• CNC routers can shape and carve wood and plastic without issue. They can create very intricate designs on most surfaces.

CNC Machine vs. 3D Printer: Speed and Efficiency Comparison

Will 3D printing replace CNC machining any time soon? That depends on how much it can speed up production times. While you don’t need special tools or setup to 3D print, the production times are longer. 3D printers can run unsupervised and can print several objects simultaneously, but building something one layer at a time can be slow. That’s why they’re not very suitable for large-scale production.

On the other hand, CNC machining can produce a lot of parts quickly. The setup time is longer because you must program the machine to follow an exact tool path. Once you have your CNC code down, the machine can keep producing parts without stopping. It also cuts out the components one at a time but at high speeds.

Both methods can help you scale up your production if you buy several machines to work at the same time. However, CNC machines are still better suited for making large volumes of parts, while 3D printers are ideal for low-volume production and customization.

Precision and Tolerances

The reason everyone in manufacturing uses CNC machines is because of their precision. They can make the same component repeatedly, and each one will have the exact same dimensions. You can instruct it to produce parts with complex geometries and tolerances as tight as ±0.01 mm, and the CNC machine will do it with utmost precision.

Using a 3D printer, you can create even more complicated shapes, but the typical tolerance is around ±0.05 mm. However, your final precision depends on what kind of printer you’re using and even the material. If you want to improve the tolerances, you might need to do some post-processing and sand down the components. It will remove the layered texture and improve the surface finish.

CNC machined parts don’t usually require much polishing or surface work. They usually come out completely smooth, but you can add texture to them if you want.

Material and Design Flexibility

Do you need to make a sphere inside a cube, sitting inside a pyramid for some reason? You can 3D print it, no problem. It’s the way to go when you want to create incredibly intricate designs and even organic-looking shapes. The layer-by-layer approach makes it easier to create complicated internal and external features.

CNC machining can also create complex geometries but can only cut out flat shapes you need to assemble. The complexity of the design is limited by how far the cutting tools can reach and their range of motion. Newer multi-axis machines make it possible to machine parts with undercuts and more complex surfaces.

Even if CNC doesn’t have as much design flexibility, it makes up for it in material selection and part durability. 3D-printed parts can be more flimsy, especially if you’re using cheaper plastic filaments.

3D Printing vs. CNC Cost Comparison

Another significant difference is the cost of the equipment. 3D printers are smaller and have fewer extra tools or attachments. They are the more affordable option, especially for hobbyists or smaller shops. CNC machines can cost several thousand and come with extra costs, like programming and different tooling. But thanks to their production speed, you can earn back your investment quickly.

Applications in Different Industries

While many industries use both manufacturing methods, 3D printing is the way to go if you want a rapid prototype with many iterations. But what it’s really leaving its mark on is medicine. If a patient needs a custom prosthetic or a replacement joint, there is a way to make it without too much waiting. There are even “bioprinting” experiments to make tissues like bone, cartilage, and organs.

CNC machining is a staple for the aerospace and car industries. It creates reliable and accurate parts with high repeatability. Landing gear for planes and car suspension must be reliable and precise down to a micrometer, and CNC machines guarantee that for each part.

But why choose between the two when you can join their forces? You can 3D print complex patterns or molds and produce them using CNC machines.

3D Printing va. CNC Machining: Which One Is Right for Your Project

To make more complex products, it’s better to 3D print them. But if you need a large amount of them quickly, CNC machining will be more cost-effective. You also need to know what material you want to use because there isn’t much overlap between the two methods.

3D printing is the better choice when you need:

• Highly complex or customized designs
• Low-volume production or prototyping
• To work with unique materials

Go with CNC machining when you need:

• High precision and tight tolerances
• Strong, durable parts
• Large-scale production

The Choice Is Yours

Regarding their use and usefulness in manufacturing, there isn’t a clear winner in the “3D printing vs CNC machining” stand-off. Both have earned their place, and there is no doubt they will continue helping designers and manufacturers make their ideas real.

Which one you choose to use is really down to personal preference. So, think about what you’re making and use the technology that makes the most sense with your current project.