CNC Machining Services
CNC Machining is a subtractive manufacturing process that involves using high speed, precision machines to remove plastic or metal from a block (“blank”) to create the design of a part. The machines use a variety of cutting tools, and are controlled by computers. The “CNC” in CNC machining stands for Computer Numerical Control. Machines commonly controlled in this manner include vertical milling machines, horizontal milling machines, lathes, routers and grinders.
The computers and control consoles used to control the machines make the CNC machining process unique. CAM (Computer Aided Manufacturing) programming instructions tell the machine how to move. The software works in conjunction with the CAD (Computer Aided Design) model of the part provided by the customer. The machines are programmed with CNC machining language (called G-code) that controls machine features like feed rate, coordination, location and speeds. With CNC machining, the computer controls the exact velocity and positioning of the tools.
The first step in the CNC machining process is that the CAD model for the part is loaded into the CAM software. Tool paths are generated based on the geometry of the part, and the software tells the machine how fast and where to move in a 3-, 4- or 5-axis coordinate system.
CNC machining has many advantages. It is a more precise process than manual machining, and it provides exact repeatability. Because the computer controls the machine movement, the machine tools can all move precisely and simultaneously on their axes to create complex, three-dimensional shapes that would be almost impossible with manual machining. These qualities make CNC machining a good manufacturing process for jobs that require a high level of precision or repetition.
For plastic parts, due to the materials available and the production process itself, CNC machining can produce more robust parts compared to 3D printing. Therefore, they can be subjected to the same conditions as the eventual injection molded production parts.
Materials for CNC Plastic Machining
CNC machining is a good choice for making prototypes and low-volume plastic parts. Since CNC machining can be done with different materials than used in the 3D printing process, for example, it is frequently used for situations where the prototype needs to be tested under the same conditions as the injection molded production parts will be in, and thus made of the same material. There can also be better structural integrity of parts that are CNC machined compared to 3D printed, due to the nature of the manufacturing process.
We currently offer the following materials for CNC machining:
- ABS, Black
- PMMA (Acrylic)
- PTFE (Teflon)
Sometimes you may require additional processes done to your parts after they are CNC machined. We have the capability to perform many post-milling processes for you, such as painting and silk screening.
This can be especially useful for show pieces. There may be times when you need prototypes to have a special treatment because they are going to be used for a presentation to a customer, for internal use within your organization, or to display at a trade show.
The following is a list of the standard secondary processes we can do, which are available for selection in a dropdown menu in our interactive quotation system. In addition, we would be happy to discuss any custom process needs you may have.
- Silk screening
- Higher tolerance than +/- 0.01″ (0.254mm)
- Custom processes
CNC Machined Plastic Tolerances
By its nature, CNC machining produces very precise parts with tight tolerances. Since the machines are computer-controlled, the method provides for high repeatability and is a good method to produce complex parts.
We will typically hold all tolerances to within +/- 0.2mm – 0.3mm. If there are critical areas on your part where tight tolerances are extremely important, you can specify that we hold tolerances tighter than 0.01″ (0.254mm). This is an option in the Secondary Processes dropdown menu in our CNC machining quotation system.
CNC Machined Metal Tolerances
Our standard tolerance for CNC machined metal is +/- 0.002″, and you can also request tighter tolerances.