1. Accurate measurement of dimensions
A significant advantage of CNC machining is the high level of tolerance and repeatability. CNC machines are capable of producing parts ranging in size from very small to extremely large. Because of the shape of CNC tools, the inner corner of the part is always rounded, whereas the outer surface can have sharp edges and be machined to a very thin thickness due to their design.
3D printing systems with varying degrees of dimensional accuracy are available on the market. Industrial-grade 3D printing has the ability to produce parts with extremely tight tolerances. It is possible to print the key dimensions in 3D and then process them during the post-processing stage if a small gap is required. A 3D printing unit's minimum wall thickness is limited by the size of the end effector it uses as a support structure. Due to the fact that custom 3D printing are manufactured one layer at a time, layer lines may be visible, particularly on surfaces.
2. Substances and materials
Besides metals, CNC processing is compatible with a wide range of materials including thermoplastics, acrylics, cork and hardwoods, styling foam, and processing wax. Excellent mechanical and thermal properties, as well as fully isotropic behavior, are demonstrated. This is due to the size restriction of the blank size (the use of a non-standard blank size will raise the cost of the product).
Plastics are the most commonly used materials for 3D printing, with metals being used less frequently. Ceramics, wax, sand, and composites are all materials that can be used to make parts in some technologies. A diverse range of materials with a diverse range of physical properties are available.3D printing is a viable option for difficult-to-process materials (such as TPU and metal superalloys). Mechanical properties of CNC parts may be inferior to those of conventional parts (because they are not always completely isotropic).
3. The complexity of the model
When designing parts for CNC machining, many considerations must be taken into account, such as tool entry and clearance, holding or mounting points, and square corners that cannot be machined due to the tool's geometrical configuration.
The fact that some geometries cannot be machined by CNC (even when using a 5-axis CNC system) is that the tool cannot access all of the surfaces of the component. The majority of geometries necessitate the use of rotating parts in order to access different sides. Repositioning will increase processing 3D printed parts and labor time, and it may necessitate the creation of custom fixtures and fixtures, which will have an impact on the final cost.
The geometric constraints of 3D printing are much less stringent than those of CNC. Most technologies (such as FDM or SLM / DMLS) necessitate the use of support structures, which are then removed during the post-processing stage. Using polymer-based powder bed fusion processes such as SLS or MJF, free-form organic geometries such as plastics can be easily manufactured because they do not require any supporting structures. One of the most significant advantages of 3D printing is its ability to produce extremely complex geometries.
4. The manufacturing process flowchart
When you place an order for CNC machining or 3D printing, the following is the situation that occurs behind the scenes:
In CNC machining, expert operators or engineers must first consider tool selection, spindle speed, cutting path, and part relocation before moving on to the next step. These considerations will have a significant impact on the quality and processing time of the final parts. After machining, the parts can either be used immediately or further processed.
During the 3D printing process, the machine operator first prepares the digital file (selecting the direction and adding support) before sending it to the machine, where it can be printed with little to no human involvement. Cleaning and post-processing are required only after the parts have been printed; this step constitutes the most labor-intensive step in the 3D printing manufacturing workflow.
5. The post-processing stage
Surface treatment and post-treatment methods can be applied to CNC machined Metal 3D Printing and 3D printed parts to improve the function or aesthetics of the finished parts, depending on the application.
The comparison of the process characteristics of CNC machining and 3D printing presented above is intended to be informative. You should consider the following considerations when selecting the appropriate technology for your parts, which can be summarized as the following general guidelines:
CNC machining is best suited for medium to large parts with relatively simple geometries, such as cylinders.
For the most part, 3D printing is best suited for small batches (or disposable prototypes) of parts with complex geometries. The price of CNC processing is competitive even when the quantity is small in metals, but geometric constraints must still be met when working with metals. When it comes to large quantities, other molding technologies are more appropriate to use.