CNC Machining: Everything You Need to Know
Computer Numerical Control (CNC) machining has become increasingly common in manufacturing. CNC technology offers a versatile, automated means to produce large-volume runs of high-quality parts. The high levels of accuracy and repeatability offered by CNC machining processes make it an ideal tool for most manufacturers.
What is CNC Machining?
In general, CNC machining refers to one of many reductive processes that take material away from a workpiece to fulfill a design. CNC processes use computerized controls to handle the entire machining process from start to finish, ultimately producing consistently precise parts. CNC machining equipment can follow the same sets of instructions over and over again to facilitate small or large production runs of identical pieces.
CNC machines come in multiple varieties and levels of complexity. Some machines can hold multiple tools at the time or work along X, Y, and Z axes to remove excess material from any side or at any angle.
CNC machining is used to create parts and components for almost every industry and application. This includes the aerospace industry and other highly complex industries that need machining work on large parts. Manufacturers can use this process on substrates such as:
- Composite materials
CNC machining is particularly advantageous due to its automated functionality. Automation allows the machines to operate self-sufficiently, requiring less human labor to produce accurate parts. A growing industry shortage of skilled machinists and laborers has been a primary contributor to the advancement of CNC technology in recent years.
The Three Manufacturing Processes
Generally speaking, there are three types of manufacturing processes:
- Reductive. Reductive or subtractive processes like machining take material away from a workpiece to create a design.
- Additive. Additive manufacturing processes combine or assemble different elements together to create a finished product. 3D printing is the most common form of additive manufacturing.
- Formative. Formative manufacturing bends or otherwise changes the form of the substrate to match the design requirements. Formative manufacturing includes processes like injection molding, in which the substrate is melted and then pressed in a mold to hold a certain shape. It also includes many metal forming processes, such as bending or rolling.
CNC Machining Process Overview
The predecessor to CNC machining—numerical control (NC) machining—used punched tape cards and rudimentary commands. CNC machining follows more complex commands and uses a greater variety of controls. These systems both instruct the cutting and forming tools that remove, but CNC machining equipment can follow complex, customized sets of instructions that come from complex CAD or CAM designs.
Different CNC machining equipment can handle different tools, capabilities, and operations. The CNC machining process typically includes these general steps:
1. Designing the CAD Model
Before the CNC machining process starts, manufacturers need to create the product design. Computer-aided design (CAD) software can be used to create detailed two-dimensional (2D) or three-dimensional (3D) models. These design files include details such as the geometries, dimensions, and other technical specifications of the parts. CAD software accounts for the limitations of machining processes and the properties of the selected materials.
For example, if a design contains holes formed by cylindrical tools, CAD software can inform design engineers when designs are too complex for a given substrate or identify potential problems due to limitations in the selected process. These automated checks help CAD/CAM design services and engineers avoid many potential errors during the rendering process so the prototyping stage is more efficient.
2. Converting CAD Files to Usable CNC Instructions
Once the design is complete, the design specifications need to be translated into directions that CNC machines can follow. The CAD files are run through computer-aided manufacturing (CAM) software. These programs create the programming code that CNC machines use to direct the tools during the manufacturing process. This software also pulls out information about the part geometry that operators can use to ensure the initial workpiece has the right dimensions and orientation.
These CNC-compatible sets of instructions are generally in one of two file types: STEP or IGES. They include programming languages such as G-code and M-code, which each handle specific areas of the machine tool’s functionality. G-code operations focus on the actual operation of the tools, such as their speed, the direction of movement, and how far they move. M-code operations focus on miscellaneous operations, such as powering on and off and other auxiliary functions.
3. Preparing the CNC Machine
Human operators play a much smaller role in automated manufacturing than in manual manufacturing, but they still handle important operations that the machinery can’t manage. This includes:
- Loading the CNC program file into the machine
- Adding the workpiece to the machinery spindles or vices so the machine can manipulate the workpiece
- Attaching the specified machining tools
- Inspecting the work area, machine, and workpiece
4. Executing Operations
Once the equipment is prepared and the program starts, the CNC machining equipment executes the steps and conducts machining operations on the workpiece. The program can complete the necessary reductive processes from start to finish without further operator input. Once the instructions have been completed, the part can continue through finishing and packaging processes.
Types of CNC Machining Operations
CNC machining is a very broad category of possible operations and processes. Among CNC machining operations, drilling, milling, and turning are the most common.
Drilling processes use bits with a diameter the same size as the diameter of the desired hole. The machining equipment inserts the spinning drill bit perpendicularly into the workpiece until it drills a hole of a predetermined length. More complex equipment can produce angular holes, and drilling tools can provide capabilities such as:
The milling process removes cuts of material from the workpiece by moving the material against a spinning cutting edge. The tools have multiple cutting points, and each tool spins to provide a sharp cutting surface with a different length and shape. When the workpiece is pressed against milling tools, thin strips or cuts of material are removed from the existing edge. This can create shallow cuts, wide cuts, or flat-bottom cavities to shape the part. Peripheral milling processes may cut deeper to create slots or threads into the piece’s general shape.
Turning processes turn the workpiece instead of the cutting tool. They include cutting processes such as boring, grooving, and facing. They cut excess material off of a workpiece by using single-point cutting tools precisely applied to the rotating workpiece. Turning creates cylindrical parts that have a specified diameter. Turning can create linear features both inside and on the exterior edge of the parts. These features include:
Advantages of CNC Machining
Many manufacturers prefer machining processes because they create parts or components from a single workpiece. CNC machining has several additional advantages. These include:
- Increased productivity. Facilities with CNC machining can produce parts 24/7. The machines may run continuously with little-to-no human intervention. The machines also require less space than workstations or manual machining setups, so a facility with a set square footage can have more machines running simultaneously.
- A high degree of accuracy. CNC machining uses highly detailed programming operations. The machines follow these instructions without allowing any unwanted variation or human error. The parts will be high-quality, precise, and identical. CNC machining can also produce parts with intricate, complex designs.
- Faster project completion. Every CNC machining process starts with a CAD design, so the prototyping process will be much faster. The software catches or prevents many possible design flaws or potential risks with different materials. When the prototyping and testing processes are shortened, products can go from design into production faster. CNC machining instructions can also be modified or replaced quickly, so there is little delay between changes in production runs.
- Cost-effectiveness. CAD file designs and reduced risks of manufacturing errors reduce the per-unit cost of production. CNC machining also requires less human labor, which further reduces the price of manufacturing the products.
CNC Machining from Pro-Type Manufacturing
For customers seeking a complete manufacturing solution, Pro-Type Industries, Incorporated offers a level of value and process flexibility that is unmatched in the industry. We operate a state-of-the-art facility that is equipped with some of the most advanced CNC machining systems available.
These are high-torque, high-RPM systems that deliver precision and productivity all in one package. One example is our 550 mm Toyoda CNC 4-axis horizontal mill. This state of the art system features spindle speeds up to 15,000 RPM delivered through a 30 HP motor. With a 30” work cube and 2400” per minute positioning, it can power through materials such as aluminum, steel, and plastics at high speeds with maximum accuracy. It also allows us to work with hard-to-machine materials such as Inconel, Invar, Monel, and various superalloys.
However, this is only one of our many precision machining systems. We also operate four CNC vertical mills that can accommodate workpieces up to 64” by 32” by 25”, two horizontal mills equipped with multiple pallets, and a high-output CNC lathe with auto bar feed, sub-spindle, and live tooling. In the hands of our team of seasoned machinists, these high-precision machining can deliver tolerances within ±0.0005”. All of these capabilities and resources are augmented by in-house fabrication of all tooling and fixturing, giving us even greater control over productivity.
Through our nearly 50 years as a manufacturer, we have learned that few project requirements consist of machining only. To add even more value to our service offerings, we also provide value-added services such as:
- Complete assembly
- Comprehensive dimensional reports
- Material traceability
All of our work is backed up by a robust ISO 9001 quality management system and culture that extends to every part of our organization.
From a single prototype to high volume blanket orders that span many months or longer, the key to our success is our ability to provide the same level of value and quality regardless of run size or design complexity. To learn more about all of our manufacturing capabilities, or to request a quote, contact us directly.