CNC (Computerized Numerical Control) provides the best option for anyone looking for high precision high quality and accurate parts. It has been around since the 1950s and has gone through many changes to come up with the exact precision that we have today. The process in CNC machining is simple, and it starts with a big piece of raw material. Then using a tool, it mills away the material along the computer indicated path to make the part. The preprogrammed tool path has the ability to make the precision cut and repeatable dimensions in different kinds of materials.
Since CNC machining services are often used in low volume manufacturing and ultimate application of parts, it is also used now as a finishing process for 3D printed products (additive manufacturing technology). Manufacturers will have the plastic or metal parts printed using 3D technology and then use CNC machine to finish them. Here are the reasons why.
Dimensional Accuracy
For industries that require high tolerance and functional requirements like automotive, consumer products and medical products manufacturing that needs to comply with repeatable and very tight specifications. Most additive technologies such as Direct Metal Sintering (DMLS) and Fused Deposition Modeling (FDM) can achieve tight specifications, but these are not enough in some critical features of the part. CNC machining can lower the tolerance and is more appropriate when producing any in-process tool or manufacturing fixture.
Speed
Another reason why many companies are combining 3D printing with CNC machining services is that of speed. Even if you include the print time, set up of CAD/CAM and the machining, the whole process is still quicker than opting for designing and creating the mold for injection molding. In addition, CNC machining combines with 3D printing can also provide engineers with flexibility in making design improvements. The process will only involve updating the CAD/CAM files and then do the same method of making a new part. In making changes in injection mold will take longer and more expensive which will cause major production lags.
In CNC machining of 3D printed parts the most familiar technique used is vertical or horizontal 3-axis milling for the reason that it can move in the X, Y, and Z planes. If the 3D printed material has more complicated geometries and features, the 5-axis milling is recommended because it can tilt and rotate on A and B axis so that it can reach the undercuts and minute features.
The parts that produced using direct metal laser sintering (DMLS) are designed for many applications therefore that always finished with multi-axis milling. This results in precise surface dimensions. In the expensive production of metal parts, the micro-machining process is applied to create a mirror-like quality. Micromachining here is combined with a chemical reaction to having a highly polished surface. This mirror-like surface is required most often in rubber gaskets for creating a tight seal.
Using CNC machining services as a secondary process for 3D printing provides more dimensional accuracy and a faster production process as compared to injection molding.