Key Considerations When Choosing Between CNC and 3D Printing For Your New Parts

March 29, 2022

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Earlier, if your project included complex parts where standard methods could not accomplish, CNC machining was always the first choice. It allowed manufacturing fairly complex parts with multiple degrees of freedom. Sophisticated numerically controlled CNC machines can cut and spin in many directions with very high precision.

However, the latest 3D printing methods provide a solid alternative to CNC machining using solid materials. Choosing between CNC machining and 3D printing became manufacturing time and cost. Each technology has its benefits, but there are a few areas where it is a better choice. Let’s go through several key points where technology is a better choice.

 

Surface Finish

Surface finish and minimal detail depend on the tool size of CNC, and 3D printing detail similarly depends on nozzle diameter in extrusion-based printing. Other 3D printing technologies such as Selective Laser Melting (SLM) can produce very detailed prints but are more expensive and produce a rough finish. Milling and turning operations of CNC machining can produce shining surfaces and, in many cases, is the preferable way to accomplish where smoothness is preferable.

PCBWay offers a wide range of CNC machines and 3D printing services to provide high tolerances and finishes. CNC tolerances can reach up to ±0.125 mm, while 3D printing accuracy can reach ±0.05mm. Tolerances highly depend on operation used, part size, and material.

After the part is manufactured, the surface can be additionally processed to achieve the desired finish. Here at PCBWay, CNC parts can be finished in multiple ways, including:

• Plating with different materials
• Painting
• Sanding
• Laser engraving
• Etching
• Oxidating
• Anodizing
• And more

3D parts might be finished in the following ways:

• Cleaning
• Sanding
• Chemical soaking
• Waterjetting

The Shape

The shape is probably the most significant key factor in selecting 3D printing. CNC machine tools are excellent for working with outer surfaces and drilling holes, while 3D printers can make almost any inner structures and weird shapes. 3D printing can produce strong but lightweight components crucial in the aerospace and automotive industries by manipulating the structure inside the part. 3D printing also allows building 3D-shaped carcasses for growing artificial human organs such as livers, kidneys, and hearts. However, 3D printing is limited in prototype size; in many cases, this problem is solved by printing separate parts and joining them into a single piece.

 

At PCBWay, there are manufacturing size constraints. For instance, for CNC machining minimal part size is 2mm while the maximum is 1000mm. The CNC limitations also include that it cannot produce interconnected parts (they have to be manufactured separately); also, CNC has limited capabilities in removing material from inside parts. If a tool cannot fit, it will not remove material from the inside. A different story is with 3D printing – technology is excellent in building almost any custom inner structure, skeleton. However, the maximum part can be 600mm x 600mm x420mm.

Strength

3D printing is additive manufacturing where structures are built layer-by-layer. Structure integrity depends on how well these layers adhere. There is always a chance of delamination under stress or other environmental conditions. Also, a limited number of materials can be used in 3D printing. Not all materials are easily temperature controlled to allow 3D printing. To increase the strength of 3D printed parts, there may be additional treatments, such as fiber reinforcement, needed. On the other hand, CNC milling uses solid raw materials such as metals or polymers. At PCBWay, you can select from over 50 types of materials for CNC machining. The hardest can be alloy, stainless, tool steels, while soft materials are aluminum and a range of plastics and resins. If you cannot see the material you need in the quote form, you can require custom. Tolls remove unnecessary areas leaving a solid monolith that can withstand much higher loads. There is no doubt that if a part needs to withstand high loads and is critical, CNC machining is the number one choice.

The Cost of Manufacturing

CNC and 3D printing machines are different technologies. One is subtractive and another additive. Subtractive technologies are more evolved, allowing to reach high manufacturing speeds, offering a wide range of materials. However, even if CNC machining, milling, or turning is highly automated these days, there is still a skilled operator needed to set up, service, and maintain smooth operation. CNC machines are equipped with automatic tool changers, coolants, and many other moving parts. CNC requires a much higher initial investment. Thus, prototyping low-volume parts may be more costly, as it needs complex setup, tooling. It is better to set up a CNC machine for higher volume production, where once set up, you can run it many times with minimal maintenance.

3D printing is created to run completely unattended, but the offer is a much slower manufacturing process. Set up is easy; all you have to do is load the G-code of your design, and it will print. Each time you can print different parts without delay on setting up. For low volume or single prototyping, 3D printing is preferable and much cheaper than CNC.

The other key factor of cost-effectiveness is how much material is used. For instance, the material is removed from raw material in CNC milling until the final shape is obtained. Some materials, such as metals and some plastics, can be recycled. In 3D printing, there is as much material used as needed. Of course, 3D printing may require some padding material and support structure if the part is very complex.

How Can You Order CNC or 3D Printing Services?

PCBWay makes most of the industrial-grade prototyping services accessible for everyone. They have great experience in PCB manufacturing and prototyping, and they constantly upgrade their machines to be in front of quality and speed. They have a very convenient website to upload your design and order preferred service with only a few mouse clicks. For instance, if you need a 3D printing service, all you need to do is go to the quote form, select necessary parameters, and upload cad files.

 

Conclusion

3D printing seems very attractive, but the technology is developing by researching more robust materials to increase printing speed, improve surface finish. There are many outstanding achievements, but they are relatively more demonstrating new capabilities than being acceptable due to economic constraints. 3D printing is more accepted by hobbyists and non-critical parts developers.

CNC machining is mainly used in industrial applications as it provides reliable, well-finished, and precise parts and can produce higher volumes in shorter times. The initial setup and tooling make CNC machining more expensive than 3D printing. However, high automatization makes it accessible to everyone.

We highly encourage you to check out all rapid prototyping capabilities at PCBWay. Besides CNC machining and 3D printing also offer sheet metal fabrication and injection molding.