Better-Mold Industrial Co.,Ltd specializes in precision CNC machining but also offers 3D printing and a full range of other manufacturing processes including, injection molding and vacuum casting. As a provider of both CNC and 3D print services, we are often asked, “What is the difference between 3D printing and CNC?” and “Which is better for my part, CNC or 3D printing?”.

These two processes can sometimes produce similar results in certain applications. However, their methods are very different as each process was designed to meet specific needs. It is important that you know which one best meets your requirements and while our experts will be happy to assist in determining which process is best for your product, we put together an overview of 3D printing vs. CNC machining to help inform engineers of the advantages and disadvantages of each.

CNC Machining

CNC machining is a subtractive manufacturing technology. It starts with a block made of solid material, such as metal, wood, acrylic, Delrin and other plastics. Various sharp rotating tools and cutters are used to remove the material until the desired shape is achieved. CNC can produce prototypes/ small batches or large quantities.

How does CNC machining work?

To create 2D and 3D models, engineers first use CAD (computer-aided design software). Next, a computer-aided manufacture (CAM) program converts the CAD file to instructions. The post-processing program then converts the instruction into a command and transmits it to CNC for execution. It is highly repeatable, precise, and can handle a variety of materials and surfaces.

3D printing

3D printing is an additive manufacturing process that builds parts by layering material one at a time. Because the additive manufacturing process doesn't require any special tools or fixtures, initial setup costs can be reduced.

Plastic materials such as ABS: Acrylonitrile butadiene styrene (ABS) and PLA: Poly Lactic Acid (PLA) are widely associated with 3D printing but in recent years 3D printed metals and carbon fibers have become more and more common.

How does 3D printing work?

To create a 3D model, engineers first use CAD. The analysis model will often have errors such as holes or intersecting faces.

A program called a Slicer converts the 3D printer to a series of thin layers in order to prepare the model for printing. This creates G-code files. This file contains instructions for the printer to follow.

The G code file is then read by a 3D printer, which applies one layer at a time of material to create a three-dimensional object. The printing process can take hours or days depending on how complex the model is and what method was used. Sometimes components will need to be cleaned and polished before they can be used.

3D printing and CNC machining share some commonalities. For example, they all use 3D models to create 3D products according to the instructions. They can be used with OBJ and STL file types. These basic similarities aside, CNC machining can meet different needs and offer different benefits. They still have their differences.

Speed

Speed is another major difference between CNC manufacturing and additive manufacturing. CNC processing is quicker when mass producing products because it involves the entire assembly line of each machine that produces each piece. The 3D printer produces the entire product from start-to-finish, making it unsuitable for mass production. 3D printing from scratch is more time-consuming than subtractive processes of removing material from existing blocks. It is important to note that industrial 3D printers have come a long way and mass production is possible in some cases.

Precision

CNC machining is extremely repeatable and has tight tolerances. All sizes of parts can be CNC machined precisely. Different 3D printing systems provide different dimensional accuracy. Parts can be produced by industrial machinery with extremely tight tolerances. When tight gaps are required, key dimensions can be oversized using 3D printing and then processed in post processing. CNC rolling mills can process aluminum and other materials more accurately than FDM. FDM is also susceptible to heat deformation.

Complexity

Many restrictions should be taken into consideration when designing CNC-machined parts. Because the CNC machine tool can't access all surfaces of the part, it cannot be used with certain geometries even with 5-axis CNC systems. For most geometric shapes, rotating parts are required to reach different sides. Repositioning can increase labor time and processing times. It may also require custom fixtures and fixtures which could impact the final price.

3D printing is almost as flexible as CNC. FDM and SLM/DMLS require support structures. These are removed after processing.

A powder bed fusion process that uses polymer-based materials can easily produce organic shapes without the need for support. 3D printing offers many advantages, including the ability to create complex geometric shapes. Part merging is possible, where multiple parts can be combined to create a part design that reduces the number of molds.

Waste

The amount of waste that they produce is one of the key differences between additive and subtractive manufacturing. Because CNC processing can remove materials, it will eventually generate a lot of non-recyclable waste. It can be messy to clean up. 3D printing is more efficient than traditional methods because it only uses the materials necessary to make the part. Because the 3D printer only uses the right amount of material to create the part, there is no need for cleanup afterwards. Because 3D printers do not vibrate, they produce less noise.

Application

CNC milling is the best option for manufacturing workpieces that are strong, precise, and/or resistant to heat. 3D printing can be used for bioprinting and food printing as well as construction and other purposes.

Cost

A CNC machine can be used to produce small quantities of parts. However, mass production is more affordable than if the part was manufactured in smaller amounts. CNC machines are a great choice for mass production.

3D printing is cost-effective because the output cost per unit does not change with the batch size. While small quantities of items can be advantageous, the cost per unit is a benefit. However, mass production may cause product consistency issues.

The complexity and accuracy of the output will affect the cost per unit of the product when CNC machines are used. Complex CNC output will have a higher cost because of the more tool paths needed, the smaller number and time it takes to complete. No matter how complex the unit is, 3D printing jobs cost the same.

At Better-Mold Industrial Co.,Ltd we have decades of manufacturing experience and our plant leverages the very latest machines in CNC and 3D printing to produce high quality parts on time and on budget. Upload your files to start your job today or contact us for a completely free DFM quote.