CNC Milling Technology

What Is a CNC Milling Machine?

CNC Milling is a subtractive process and though a technological wonder, it’s kind of like sculpting. There are a couple of quotes associated with artists that seem appropriate regarding CNC Milling. The first is “Sculpture is the art of the intelligence” (Pablo Picasso) and the second “Everything is sculpture. Any material, any idea without hindrance born into space, I consider sculpture” (Isamu Noguchi). CNC manufacturing of precision parts is a technology driven industry and incorporates highly intelligent machines and skilled machinists to operate them. The resulting CNC machined components are sophisticated that each is a modern marvel and perhaps functioning works of art. These machines can transform raw material into intricate shapes with unparalleled accuracy and repeatability. At its core, a CNC Mill consists of a rotating cutting tool mounted on a spindle. This spindle can move in three axes (X, Y, and Z) to position the tool relative to the workpiece. When these movements are coordinated with precise timing, spindle speed, and depth, CNC precision parts are produced. The control is done though CAD programing or Computer Aided Design files. Specific software programs input customer generated files or create custom cad files per a customer’s requirements. CNC Milling can process raw materials like tungsten, stainless steel, copper, titanium, aluminum, brass and others including plastics and ceramics. Customers seeking CNC technology or CNC Milling, do so for prototype support and product development, but also for the capabilities these machines have in providing the platform for high volume manufacturing.

The Basics of CNC Mills

Regarding CNC Milling, the CNC stands for “Computer Numeric Control”. A CNC Mill removes material forming features such as holes, slots, threads and creates rounded corners, chamfered edges and recessed features. The mechanisms involved are a host of steps and tools that require mechanical engineering knowledge for operation, but also knowledge of materials and how they react to the conditions incurred during the milling process. Precision CNC machining parts can look straight forward and relatively easy for first time observers and this is due greatly to the experts in the industry, who have accumulated vast amounts of experience and firsthand knowledge. They do make it look easy, but it is a collection of processes that involve following an encoded software program, often referred to as G-code. This code dictates the movements of the cutting tool.  Some tools resemble drill bits with cutting edges on the sides, others like face mills that have flat cutting edges for planar surfaces, and ball-nose end mills for creating curved shapes. These tools are mounted on a spindle and can move along three axes (X, Y, and Z). The machine’s computer interprets the G-code and translates it into physical actions, resulting in CNC machined components. To further explain, let’s look in depth at how CNC Milling works.

How CNC Milling Works-A Step by Step Guide

Following established guidelines and processes are the basis on how CNC precision machining parts are done. There are no shortcuts but there are certifications like ISO 9001 or AS9100 that manufacturers use to keep the integrity high on the quality of all manufactured CNC machined components. Though these listed steps differ from one manufacturer to another, the process within each is followed for not only quality and superior product performance but also for the internal safety of the employees.   

1. Design and Planning

• CAD Modeling: Create a detailed 3D model of the desired part using computer-aided design (CAD) software.
• Material Selection: Choose the appropriate material for the workpiece based on factors like strength, machinability, and cost. Common materials include metals (aluminum, steel, brass, titanium, copper), plastics, and wood.

2. Toolpath Generation

• CAM Software: Use computer-aided manufacturing (CAM) software to convert the CAD model into G-code.
• Toolpath Optimization: The CAM software determines the optimal path for the cutting tool to follow, considering factors like tool size, cutting speed, and depth of cut.

3. Machine Setup

• Workpiece Clamping: Secure the workpiece to the machine’s table using clamps, vices, or other holding devices.
• Tool Installation: Mount the appropriate cutting tool (e.g., end mill, ball nose mill) in the spindle.
• Zero Point Calibration: Set the reference point (zero point) for the machine’s coordinate system.

4. Machining Process

• G-Code Execution: The CNC machine’s controller reads the G-code and controls the spindle’s rotation and the tool’s movements.
• Material Removal: The cutting tool removes material from the workpiece, following the specified toolpath.
• Coolant Application: Coolant is often used to lubricate the cutting process and prevent overheating.

5. Post-Processing

• Deburring: Remove sharp edges and burrs from the finished part using hand tools or automated deburring equipment such as tumble deburring, acid cleaning, micro-etching.
• Finishing processes such as electroplating, anodizing, powder coating, and other methods can improve the part’s appearance, add corrosion resistance, and increase a component’s resistance to wear thus increasing the life span of the part.
• Inspection: Verify the part’s dimensions, tolerances, and overall quality using measuring instruments.

Notes on Design and Materials:

• DFM in the CNC industry stands for Design for Machinability. When new projects come forward a review of the geometry, material, tolerance and other details will determine how well the proposed component will manufacture within the capabilities of the CNC Milling system. Concerns or cautionary notes will be discussed with the customer prior to manufacturing.
• The choice of material significantly impacts the machining process. Harder materials like steel, tungsten, and titanium will require more powerful tools and slower cutting speeds.
• Workpiece hardness can also affect tool life and surface finish.
• The material’s machinability rating provides an indication of its suitability for CNC milling.

The CNC Milling process is a very coordinated effort between all parties involved including the raw material providers, the customer and the CNC machining parts manufacturers. To oversee the process is done to the highest quality standards, many CNC shops are certified through ISO 9001, which is a quality management system. Other certifications like AS9100 are done when CNC manufacturers work directly with the aerospace industry and ISO13485 focuses on medical device manufacturers. These certifications enable CNC machining parts manufacturers to provide the ultra-high quality needed for so many of the products and services. Though each CNC manufacturing process will vary, the key in these processing steps is quality control, repeatability, accuracy and production volume support.

Types Of CNC Mills

CNC Milling machines are made in different sizes, functions and capabilities and include Horizontal Milling, Vertical Milling, Knee Milling and Bed Milling machines and others. These machines producing CNC machined components have some overlap of functionality occurring between them, but CNC machining parts manufacturers choose the best format to suit their business model and areas of expertise. No one type is better than the other, rather they are utilized for the projects requirements and sometimes using more than one system type is needed to complete a component. Other factors such as production capacity, work piece size and budget all are factors for consideration on CNC manufactures when considering using or purchasing this type of capital equipment. The following table highlights the different CNC Milling types:

Precision CNC machining parts can be very satisfying as the resulting product or system can be a great benefit to the end user. Imagine the amenities and services we have both at home and through professional services, we are in part recipients of the high quality and reliable services and products provided by CNC technology. For manufacturers, choosing the appropriate CNC Milling method allows for costs to be controlled through production capacity, efficiency and capabilities from these unique machines. Being part of the CNC precision parts industry directly supports the global economy that always seeks greater technological breakthroughs and continues to seek out this industry for support.

Benefits Of CNC Mill Machining Processes

CNC machining parts manufacturer’s benefit from using this technology as it gives great precision, repeatability and material versatility along with other factors. With demands for high quality and being able to support production supply streams, manufacturing requires reliable methods that can support small R&D and prototype development and have the capacity to take these qualifying runs into mass production. There are many good reasons why CNC Milling, and the CNC industry has grown in revenue over the past 50 years and the benefits this technology provides is a key element to that success. With ever increasing innovative designs and demands for faster turn times, manufacturers rely on this technology to produce high quality CNC machined components. Some of the benefits of using CNC Mills are:

Customers also benefit by using CNC Milling technology.  Upon placing their project in the hands of these professionals, cost reductions, quality improvement and flexibility are some of the advantages gained such as:

The precision CNC machining parts industry has revolutionized manufacturing by offering a highly efficient, precise, and versatile method for producing a wide range of components.  CNC milling has become an indispensable tool in modern manufacturing, providing benefits that contribute to improved product quality, reduced costs, and enhanced competitiveness extending to both manufacturers and customers.