CNC machining and 3D printing are both widely used technologies for creating Rapid prototypes, and they each have unique advantages and application scenarios. When choosing CNC machining or 3D printing, several factors need to be considered including part complexity, material selection, processing time, cost, and more. In this article, KUSLA provides some detailed suggestions to help you choose the most suitable method for your specific prototype project.
WHAT IS CNC MACHINING?
CNC machining (Computer numerical control machining) is a method of cutting material blocks by computer-controlled machine tools. It is characterized by high precision, high-quality parts manufacturing. CNC machining can be applied to a variety of materials, including metal, plastic, etc., suitable for the production of complex parts and precision parts.
Advantages of CNC machining
- High precision: CNC machining can achieve very high accuracy and dimensional consistency, suitable for the manufacture of parts requiring strict size and geometry.
- Wide range of materials: CNC machining can work on a variety of materials including metal, plastic, ceramics, and so on.
- Strong applicability: CNC machining is suitable for the production of small batches or small and medium-sized parts with strong flexibility.
Disadvantages of CNC machining
- Time and cost: CNC machining usually requires a long processing time and it is expensive especially when producing large quantities.
- Material waste: Due to the need to cut out parts from block materials, material waste will be generated.
WHAT IS 3D PRINTING?
3D printing is an additive manufacturing process that adds materials layer by layer to form the desired product. This process requires no special tooling or fixtures and can create complex structures. With laser energy or a heated extruder, material layers are solidified to form the prototype.
Advantages of 3D printing
- Rapid prototyping: 3D printing can quickly produce samples and prototypes, speeding up the process of product development.
- Customized production: 3D printed products can be customized according to demand, suitable for small batch production and personalized customization.
- Complex structures: 3D printing can manufacture complex internal structures, thin walls, and geometric shapes that are difficult to achieve with traditional processes.
Disadvantages of 3D printing
- Accuracy and surface quality: The accuracy and surface quality of 3D printing are poor compared with CNC machining, and are not suitable for parts with high precision requirements.
- Material limitations: 3D printing materials are limited and may not meet specific material needs.
- Production batch: 3D printing is suitable for small batch production, but may not be efficient in large-scale production.
How to choose between CNC vs 3D printing
CNC machining and 3D printing have their own advantages, and the choice of machining method depends on the specific application scenario and needs. In practical applications, the most suitable machining method can be selected according to below factors:
Material
CNC machining material is available from plastics to metal. The materials you can use with CNC machining include plastic materials like ABS, Nylon (PA66), Polycarbonate (PC), Acrylic (PMMA), Polypropylene (PP), POM, and PEEK and metal materials include aluminum alloys, steel, stainless steel, titanium, and brass.
3D printing materials mainly include liquid resin (SLA), nylon powder (SLS), metal powder (SLM), plastic Filament (DFM), etc.
So, if your prototype needs better material properties close to production materials, CNC machining will be better for your prototype project.
Geometric
CNC machining is subtractive manufacturing, through various high-speed cutting tools, cutting out the required parts according to the programmed cutting path. This means CNC machining can only process rounded corners with a certain radius, but cannot directly process inner right angles due to the radius of the cutting tools.
3D printing is an additive manufacturing. it can effectively process and produce parts with complex structures, such as hollow parts, while CNC machining makes it difficult to process hollow parts. Therefore, 3D printing is a better choice when the parts have complex Geometry and a sharp corner requirement.
Precision
CNC machining offers tight tolerance and excellent repeatability. Different 3D printing methods offer different dimensional accuracy. below is a table to show some of the properties of CNC machining and each type of 3D printing method. you will find that if you need a high-accuracy prototype, CNC machining will be your choice.
| Technology | Tolerance | Minimum wall thickness | Maximum part size |
| CNC machining | ± 0.01 – 0.125 mm | 0.75 mm | Milling: 2000 x 800 x 1000 mm Lathe: Ø500 mm |
| SLA 3D Printing | ± 0.2 mm | 0.7 – 1.0 mm | 300 x 300 x 300 mm |
| SLS 3D Printing | ± 0.3 mm | 0.7 – 1.0 mm | 300 x 300 x 300 mm |
| FDM 3D Printing | Desktop: ± 0.500 mm Industrial: ± 0.200 mm | 0.8 – 1.0 mm | Desktop: 200 x 200 x 200 mm Industrial: 900 x 600 x 900 mm |
| SLM/DMLS 3D Printing | ± 0.100 mm | 0.40 mm | 230 x 150 x 150 mm |
Surface Quality
3D printed plastic part (left) and CNC machined plastic part (right)
In terms of surface quality, CNC is better than 3D printing. CNC machining can produce workpieces with a high surface quality with cutting tools. In opposite, the layer-by-layer printing process of 3D printers leaves a rough surface texture on the workpiece.
Cost
the cost of CNC machined prototypes is generally higher than 3D printed prototypes. this is Because CNC machines are more expensive than 3D printers and CNC machining uses more time to build a prototype.
Speed
CNC machined prototypes usually need around 3 days while 3D printed prototypes need less than one day. So, 3D printing can make rapid prototypes faster than CNC machining.
Conclusion
If you need high-precision prototypes, CNC machining is the best choice. if you need a prototype fast and low cost, 3D printing is better for you. KUSLA is a leading prototype manufacturer in China, we can provide CNC prototyping service and 3D printing prototyping service to help you get your prototypes done quickly.
You may also interested in other plastic parts manufacturing process comparisons
- Urethane casting vs injection molding
- CNC Machining vs Injection Molding
- CNC Machining vs Urethane Casting
FAQ
Is CNC better than 3D printing?
there is no absolute answer. it depends on the specific situation such as the characteristics of the parts, material requirements, production volume, and costs.
What’s better than 3D printing and CNC machining?
For small volumes, Urethane casting is a better choice for making the plastic parts. For large-volume plastic parts making, injection molding will be a good choice.
