3D printing rapid prototyping services are widely used in many industries. It has many advantages compared to traditional manufacturing processes. But it also has some limitations. For example, it is not cost-effective for mass production, limited by its production speed and accessibility. As for CNC machining, it is another widely-used manufacturing method for low-to-medium production. What are the differences between these two methods in rapid prototyping and small-batch manufacturing? This article is to find out.

3D printing is a form of additive manufacturing while CNC machining is subtractive. This is their biggest difference. 3D printing builds products by adding the materials layer by layer. It is favored by its greater freedom of shape, rapid production of a small batch of products, and the ability to cut costs and weight in products. In comparison, CNC machining creates products by cutting away materials using cutters and spinning tools. The advantages of this manufacturing method include greater dimensional precision and more machinable materials, such as metal, plastic, and wood.

3D Printing vs. Precision CNC Machining Services: Materials Available

Whether you choose 3D printing services or the more precision CNC machining services, there are a wide variety of materials for you to choose from. But 3D printing focuses more on plastic materials. The commonly used 3D printing materials include plastics like ABS, Nylon, PLA, ULTEM, photo-polymers like calcinable, wax, and biocompatible resins. Some specialized 3D printers can also work with sand and ceramics. Metal parts can also be 3D printed today. The common metals used include stainless steel, titanium, aluminum, and Inconel. However, the metal 3D printing service is often expensive. The good news is that with the constant development, metal 3D printing technology is also becoming better and more affordable. Nowadays, 3D printing rapid prototyping services are popular in plenty of industries, including jewelry, aerospace, automotive, medical, etc.

While 3D printing is more used to make plastic parts, CNC is mainly used for machining metal parts. But it also can be used to process plastics. The common materials used for CNC machining are as followed: plastics including ABS, Nylon (PA66), Acrylic (PMMA), Polypropylene (PP), PEEK, and POM, and metals such as stainless steel, alloy, aluminum, and magnesium. Aluminum is the most widely used metal materials in CNC machining. It is reusable and has good mechanical properties, heavily used to create high-quality prototypes in a variety of industries.

If you are looking for manufacturing high-quality and high-accuracy metal prototype, precision CNC machining services could be the ideal option.  (As to which material is the most suitable for your project, read this: Selecting the Right Material for Your CNC Prototype)

3D Printing vs. Precision CNC Machining Services: Dimensional Accuracy

CNC machining provides tight tolerance and great repeatability. Parts from very large to tiny small can be CNC machined with a high level of accuracy. It is due to that CNC machine is equipped with the cutting tool whose external surfaces have sharp edges. Parts can thus be cut very thin.

As for 3D printing, the dimensional accuracy of finished parts differs from 3D printing systems. The industrial printer can produce parts with high precision. But 3D printed parts cannot be as thin as CNC machined parts. The minimum wall thickness of 3D printed parts is limited by the size of the end effector, such as nozzle diameter in FDM printing or the laser spot size in SLS printing. In addition, as parts are manufactured layer by layer, the printed objects especially the objects with curved surfaces might have visible layer lines. Thus, if you have a high requirement for the surface finish and dimensional precision of your prototypes, 3d printing rapid prototyping services might not be the best choice.

3D Printing vs. Precision CNC Machining Services: Geometries Complexity

When you intend to manufacture your parts or model-ups using precision CNC machining services, there are some limitations that should be considered carefully, such as tool access, mount or hold points. In addition, due to the tool’s geometry, CNC equipment cannot machine square corners. In contrast, in 3D printing, there is almost no restriction in the printed object’s geometry. But in some 3D printing technologies, such as FDM, DMLS/SLM, support structures are required. Being able to create parts of highly complex geometries is one of the critical advantages of 3D printing. If you want to create geometrically complex prototypes, why not try 3D printing rapid prototyping services.

3D Printing vs. Precision CNC Machining Services: Rules of Thumb

When you choose between 3D printing services and CNC machining services, here are a few guidelines to help you make the right decision.

1. If you want to produce a medium to high quantities of parts or mock-ups and these parts are relatively simple in their geometries, then precision CNC machining services are best suited. Otherwise, you may opt for 3D printing.

2. When your required parts are metal, CNC machining can be more price-competitive even it is low quantities. But geometry limitations should be considered.

3. 3D printing is most suited when a fast turnaround, low cost of a small number of prototypes or parts are critical.

4. However, if large part qualities are required, neither 3D printing nor CNC machining can be a cost-effective option. In this case, you might opt for investment casting or injection molding instead.