CNC Machine VS 3D Printer Nowadays, 3D printing is ever growing technology with many pros over traditional manufacturing methods. However, as every rose has its thorns 3D printing has also its cons. It sometimes cannot be efficiently used for mass production, and has a restrained speed and accessibility. An alternative mass production mode for low-to-mid production is CNC machining (computer numerical control). Here, the benefits and drawbacks of each method will be discussed so that it will be more practical to decide where each technology is most appropriate.
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Subtractive vs Additive Manufacturing
The main difference between 3D printing and CNC machining is that 3D printing is a type of additive manufacturing while CNC machining is considered as subtractive. This proposes that CNC machining starts with a block of material (called a blank) followed by cutting away material to form the finished part. In order to do that cutters and spinning tools are utilized to make the piece into a desired shape. High dimensional accuracy and availability of compatible materials (wood, metals and plastics) are amongst the advantages of CNC machining.
3D printing are formed layer-by-layer using materials such as plastic filaments (FDM), resins (SLA/DLP), plastic or metal powders SLS/DMLS/SLM). Layers of these materials are made solid to create the finished part by using a point of supply of energy such as a laser or heated extruder. The freedom of shape, applications in many sectors, accuracy, speed, and low cost and weight in parts are among the benefits of 3D printing.
However, surprisingly there are various machines which achieve to integrate these two forms of manufacturing in one. Mostly known of these is the ZMorph 2.0 SX, is marketed as a CNC mill (also used as a 3D printer). This involves a CNC mill with 3 axes and a print head. Print head is used for its interchangeable heads. What is more, many firms have recently closed successful Kickstarter campaigns with these combined machines, such as Mooz’s 3-in-1 3D printer.
CNC Machine VS 3D Printer, The main advantageous similarity of 3D printing and CNC machining is that both are adaptable with a wide range of materials, inclusivity of both plastics and metals. However, 3D printing is more centered on plastics. Although, this is shifting quickly taking into consideration that better and cheaper ways of 3D printing metal are being improved continuously by producers such as 3D Systems, Arcam, Desktop Metal and Markforged.
ABS, Nylon (PA66), Polycarbonate (PC), Acrylic (PMMA), Polypropylene (PP), POM and PEEK are most frequently type of plastics used in CNC. Aluminum, on the other hand, is the most commonly used metal. In order to create first-rate prototypes in a diverse industries, aluminum is used by prototyping companies. Moreover, aluminum is recyclable, has good protective qualities, and can create impressive prototypes for machining. Other frequently used metals include stainless steel, magnesium alloy, zinc alloy titanium, and brass.
Commonly used thermoplastics used in 3D printing involve ABS, LA, Nylon, ULTEM, as well as photo-polymers such as wax, calcinable or biocompatible resins. What is more, some niche 3D printers also have the ability to print of parts in sand, ceramics, and even living materials. 3D printing mostly uses metals such as aluminum, stainless steel, titanium, and inconel. One should also mention that in order to 3D print metal, very expensive ($100,000+) industrial machines are needed. CNC cannot produce some materials such as superalloys or TPU (flexible material), so to produce that 3D printing or rapid tooling technology should be used.
What is Ease of Use?
3D printing is practical to use than CNC machining. The reason behind this is that once the file is prepared, all you need to do is to choose the part orientation, fill, and supports. Then once printing has started, no care is needed and the printer can be left until the part is completed. However, post-processing demands relays on the technology.
Yet, CNC machining is a process where more labor work is needed. Highly skilled manager is needed to prefer different and right tools, rotation speeds of tools, the cutting path, and any repositioning of the material. Post-processing techniques may also need more time if desired.
Accuracy, Size limitations & Geometric Complexity
Even though there are various 3D printing technologies, here we will compare CNC machining with SLS, industrial (not desktop) FDM, and DMLS metal 3D printing. When tolerance is taken into account, CNC machining is better than all 3D printing processes, even DMLS. Nevertheless, with minimal layer thicknesses the superiority is not so weighty, and is not as accurate as DMLS.
|Tolerance (mm)||Min. Layer Thickness (mm)||Max. build volume (mm)|
|CNC Milling||± 0.025 – 0.125 mm||cutting depth 0.01 mm||2000 x 800 x 1000 mm|
|SLS||± 0.3 mm||0.7 – 1.0 mm||300 x 300 x 300 mm|
|Industrial FDM||± 0.5 mm||0.8 – 1.0 mm||900 x 600 x 900 mm|
|DMLS||± 0.1 mm||0.4 mm||230 x 150 x 150 mm|
Powder bed fusion 3D printing processes, like SLS and DMLS have defined power in their build volume. FDM (technology with larger build volumes) cannot compete with CNC from the point of maximum size of parts.
3D printing is famous for its benefits in creating parts with high geometric complexity. It can form parts with geometries where not any other ordinary mass production method can create. However, for that, supports are needed for some technologies. Technologies like SLS and Multi Jet Fusion by HP is capable to do this outside of any support structures.
CNC Machine and 3D Printer Cost
Even though 3D printing is cheaper, the prices relay on the number of parts are required and how fast the customer needs them. For great number of parts (higher double digits to 100s) CNC is can do work in a more practical way. For lower volumes, 3D printing is more appropriate and cost efficient. Also, if you need prototypes or parts in a short period of time 3D printing should be chosen. However, there are extra aspects that make comparing the two technologies harder. These involve materials which vary in cost (from cheap materials like ABS to materials that can cost $500/kg like PEEK), and improving and changing machinery (such as CNC heads).
Environmentally Friendly Product
CNC Machine VS 3D Printer, Knowing that CNC includes cutting material away from an original block of material, there is always something left behind the work. These kinds of material are required to be cleaned and disposed of. Since CNC is an additive manufacturing form, there is no mess apart from supports. This makes 3D printing environmentally friendly among these two methods as there is less waste.
To sum up, there is no excellent technique taking into account that both methods have both pros and cons. The most practical one to use will be based on the material, geometric complexity, manufacturing volume, and budget. In order to discover which one is best for your specific job, it is recommended to get into contact with a local or international service, and take their advice. If you manufacture in-house, think about the machinery available to you and determine whether it is practical to do.
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