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Are you not sure which process is better for you, CNC or 3D printing? This is a situation that manufacturers normally face when they have to make a decision on a manufacturing process.
Therefore, today we will study the important difference of these two techniques to answer this exact question.
What is CNC Machining?
CNC machining refers to the method of cutting materials and converting them into the end product through computer controlled motion and tools. This process uses machines, routers and lathes and is given exact digital instructions to follow.
One of the great advantages of CNC machines is the ability to reach tight tolerances, up to minimum of 0.0001 inches. The computer controls every movement of the machine and because of this, the digital designs are converted into a perfect final product.
What is 3D Printing?
3D printing is a process in which a particular kind of material is deposited layer by layer to form an object. This can be done in different ways like SLA, SLS, FDM, and also the production of incredibly intricate parts with micron-level accuracy is possible with this technique.
Thus, 3D printing has already been used by firms in the medical, automotive and aerospace sectors for prototypes and end goods, especially for making products that require very complicated parts.
CNC Machining vs. 3D Printing: Top 10 Main Differences
Both CNC machining and 3D printing have their own advantages and limitations. And it is very important to know the differences between these two processes so that you can choose the right process according to your needs. So in this section we will look at top 10 differences between them.
1. Material Options
As far as material options go, CNC machines can work with a broad range of materials. You can easily CNC machine plastic, metal, titanium alloys, wood, and composites. 3D printing machine, on the other hand, can work with very few materials. They can only be used on resins, plastics, some metals and certain types of ceramics.
2. Manufacturing Processes
Both of these techniques provide different methods for making parts. CNC machining typically removes material from a large round block and thus creates parts. And it does this with the help of cutting tools that are instructed via G-code.
Whereas 3D printing takes a completely different approach. It builds things by adding material layer by layer on top of one another. And it uses CAD‘s information to place each layer in its correct place.
3. Material Usage
CNC machining wastes a lot of material. It normally only uses about 40% of the initial material and leaves the rest as scrap. 3D printing is much more efficient. It only uses the material that is necessary to make the part. It leaves very little waste material and that too for failed parts or support structures.
4. Design Complexity
CNC cannot make many designs due to limitations on tool access. Because to make complex shapes, you have to set up a lot of machines and even then, it is very difficult to create internal cavities without splitting the design.
3D printing performs very well here. It can easily create internal cavities, difficult shapes and lattice structures. And to create all these things, you do not have to use any extra tools and because of this your cost is also saved.
5. Surface Finish and Precision
CNC machining provides very good finishing. Through it, we can get tolerances up to 0.0025 inches and roughness up to 8 micrometers. Also, we can get even better finishes through special finishing methods such as anodizing and bead blasting.
In comparison, 3D printed parts have very rough surfaces and layer lines can be clearly seen on them. Even SLA, which is a very high quality 3D printing technology, has to undergo a lot of finishing to match the quality of CNC finish.
6. Production Speed
Today’s new CNC machines can easily remove material at speeds of over 500 meters per minute. And because of this, we can make parts in few hours nowadays. On the contrary, since 3D printing is done in the form of layers, it takes 8 to 72 hours to make any part.
It is true that setting up CNC machines takes a lot of time initially but they perform very well for mass production. 3D printing is appropriate for the production of complex and small prototypes, thus it works as a good method for this purpose. However, as the part size increases, the process needs a longer time to complete.
7. Setup and Operational Complexity
If you use CNC machining, you need to prepare so many things even before the actual process is initiated. It is important for the operator to choose the right tools, program the G Codes and secure the workpiece firmly in place. Even after this, it is very important to take care of many factors during the process such as feed rate, tool path and cutting speed.
Whereas 3D printing is much simpler in comparison. The operator only has to prepare the CAD file and then load the material. In some very complicated prints, a few extra steps can be needed like picking the best build orientation or to add load structure etc.
8. Cost-Effectiveness
When we have to make parts in very large quantities, CNC machining proves to be the most economical. As the number of parts to produce increases, the initial cost incurred in the setup becomes nothing in comparison.
Whereas 3D printing is very cost effective for prototyping and small scale production. In this, we need very less material, the cost of setting it up is very low and it can easily make even complicated designs.
9. Design Flexibility
With the help of 3D printing, we can create many different and difficult designs. It can easily create parts with walls 0.5 mm thick or even less.
CNC machining cannot make complicated designs and it has some limitations in this regard. In CNC, we need special tools to make undercuts, and apart from this, it is necessary for the tools to have a corner radius of at least 1 to 3 millimeters to make internal vertical corners. To create any design feature, we have to plan with a lot of care about proper fixing and accessibility of the tool.
10. Scalability
Whenever we need production in bulk, a CNC machine is the best option for this. It has to be programmed just once and after that it can easily make thousands of identical parts even at a speed of 500 meters per minute or more. As the production volume increases, the cost of each part decreases very rapidly.
The cost of 3D printing does not depend on quantity and remains the same no matter how much we produce. This is because same amount of material and time is required to make each part. Its the reason why 3D printing is normally preferred for small production runs or prototypes and its use in mass production is almost negligible.
How to Pick the Right Process Between CNC Machining vs. 3D Printing
One thing to always keep in mind that there are several different aspects that need to be considered when choosing the best one from CNC machining and 3D printing.
Part Complexity
The complexity of the part you want to make has a huge impact on your choice of technology. If you have to make very complicated parts like medical implants which have a cooling channel inside, then 3D printing is the better option. You will not need any special type of tool to make such designs.
And on the contrary, CNC machining is a very good option for making simple parts like brackets etc. where we need very strict tolerances. Its speed and accuracy make it a good option for making these types of parts.
Production Volume
For high volume production of parts of more than 100 units, CNC machining is more proficient and less costly approach compared to other manufacturing methods. This is because the cost you incurred in setting up the machine initially is easily divided across these parts.
And if you need to make a prototype or have a small project like 50 units or less then 3D printing gives you better value for money and its per unit cost is lower.
Lead Time Requirements
Available time to manufacture the part also matters. It takes 1 to 3 days lead time to make a simple CNC machining part. Whereas if you have to make a very complicated part, then it normally takes 2 to 3 weeks. Therefore, you should go for CNC machining only if you want highly accurate parts but the deadline is not a problem. And if you have less time and you want a quick batch or prototype, then 3D printing is a better option.
Conclusion
Your decision to go for either of these two processes depends on the nature of project you are planning. CNC machining is preferred to produce parts in large amount. On the other side, 3D printing is useful for quick prototypes and small production. Today, almost all manufacturers use both of them to get the most benefits.
RICHCONN provides both CNC machining and 3D printing services according to the customer’s needs. For more info, you can contact us anytime.
FAQs
How do 3D printing and CNC machining compare in creating complicated geometries?
3D printing is very good for producing advanced and complex geometry. CNC machining, on the other hand, gives very strict tolerances but tool accessibility problems limit the manufacturing of complicated parts.
Can both processes work with metals and plastics?
CNC machining has the ability to shape almost all of engineering materials, from aluminum to specialized types of material like PEEEK and titanium.
3D printing can only use particular materials such as thermoplastics (ABS, PLA) and metal powders for processes like DMLS.
Can manufacturers use both 3D printing and CNC technologies during manufacturing?
Yes! Many companies use both methods in hybrid manufacturing. Usually, 3D printing is used first for making prototypes or complicated features. After that, CNC machining is applied to acquire the correct dimensions as well as to give fantastic quality surface finishing.
What are the general applications of CNC machining and 3D printing?
CNC machining is used in the manufacturing of mechanical and aerospace components and producing parts in mass quantity, whereas 3D printing is mainly used for making intricate internal features, prototypes and custom medical devices.
How do mechanical properties of parts compare between the two methods?
The parts that are manufactured using CNC machining keep the properties of the material they are made from. Furthermore, parts made this way have same strength throughout the part. On the contrary, if we take a look at 3D printing, different layers have different strengths. Such behaviour is called anisotropic behaviour. Nevertheless, we can still obtain characteristics equivalent to those of CNC machined parts by using DMLS and other new techniques.
