Everything You Need to Know About the CNC Machining

High precision CNC machining center working

 

Computer numerical control (CNC) machining was invented more than 50 years ago, and since then, its high capacity for precision and automation has helped create countless products. Across industries — from defense, automotive, and aerospace, to medical, precision, and manufacturing — this sophisticated technology has become part of the world’s industrial DNA.

What does CNC machining different from traditional machining?

In traditional machining, a skilled machinist operates a machine, removing or forming metal. This is done according to specifications provided by designers and engineers, usually through an engineering drawing or blueprint. They use turn wheels, dials, switches, chucks, vices, and a variety of cutting tools made of hardened steel, carbide, and industrial diamond then use measurement instruments to ensure all of the dimensions are correct.

CNC machining performs the same function as traditional machining — metal cutting, drilling, milling, boring, grinding, and other metal forming and removal functions — but it uses computer numerical control rather than manual control by a machinist. It is automated, driven by code, and developed by programmers. It is about as precise the first time of cutting as the 500th. Widely used in digital manufacturing (and sometimes in low-volume production runs), it can be revised and altered for modifications and different materials.

This type of machining is much more precise and has largely superseded traditional machining (though not entirely) in manufacturing, fabrication, and industrial production. It uses mathematical coordinates and the power of computing to achieve the same end, with the greatest accuracy. Specifically, computer numerical control uses Cartesian coordinates. These are spatial coordinates — in several dimensions — using coordinates and axes. The automation of cutting tool machines controls its cutting, boring, drilling, or other operation using the numerical control of a computer that reads the coordinates. These coordinates were designated by engineers in the product’s digital drawing and design.

How does the CNC machining process?

CNC machining uses subtractive processes, which means feedstock is machined to final form by subtracting and removing material. Holes are drilled, lots and pathways are bored, and metal stock is shaped into new materials with varying tapers, diameters, and shapes.

For subtractive manufacturing, shapes are achieved by the subtraction of material. This contrasts with other types such as additive manufacturing — where materials are added, layered, and deformed to a specified shape. It also contrasts with injection molding where the material is injected in a different state of matter, using a mold, and formed to a specified shape.

CNC machining is versatile — and can be used with various materials, including metals, plastics, wood, glass, foam, and other composite materials. This versatility has helped make CNC machining a popular choice across industries, enabling designers and engineers to fabricate products with efficiency and precision.

Production

What types of software are used in CNC machining?

The CNC machining process uses software applications that can be divided into 3 categories:

CAD software
CAM software
CAE software

Computer-aided design (CAD) software

Computer-aided design (CAD) software is a program used to draw and produce 2D or 3D renderings of solid parts and surfaces. It also provides documentation and technical specifications associated with the part.

CAD software is becoming increasingly sophisticated. It can be used to determine the characteristics of a part, evaluate the quality of an existing part design, simulate part design, or provide design data to manufacturers and shops.

Computer-aided manufacturing (CAM) software

Simply put, CAM software programs write a digital file that the machine will process.

The software must be set up to operate the CNC machine that will then manipulate the materials to produce the required part with the greatest precision.

Computer-aided engineering (CAE) software

This is software used by engineers during the pre-processing, analysis and post-processing phases of the product development and simulation process.

These are precise assistance tools used throughout the product creation stages, such as design, simulation, planning, manufacturing, diagnosis and repair, to help evaluate and modify the product design.

Today, a single program can even combine aspects of CAD, CAM and CAE software. This type of software can manage the entire manufacturing process, from design to production, including an accurate analysis of the machined part.

 

What are the advantages of CNC machining?

We have already mentioned some of the advantages of CNC machining, but there are others. Computer technology makes it possible to work on highly complex designs that are difficult to machine on conventional machine tools. This advance has led to the development of high precision components for a variety of industries, including aerospace, marine, rail, and aviation.

CNC machining provides a significant improvement in precision, reducing errors and improving productivity. And by drastically reducing human input, the risk of workplace accidents is low. The cost savings from a reduction in metal waste are also significant. Finally, some machines are equipped with an automatic chip removal system, which allows for the cleaning, reuse and recycling of materials.

How many Methods for the CNC Milling?

There are several different forms of milling that can be used for the fabrication of parts. Plain milling, or the act of cutting flat surfaces parallel to the rotating axis of the cutting tool, was the first type of milling developed. The introduction of CNC machining has led to several other types of milling, including:

Face Milling:  Cutting material to create a surface perpendicular to the rotating axis of the cutter.

Angular Milling: Removing material from a flat surface of the workpiece at an angle.Form Milling: Cutting material to make irregular surfaces, like curves.
Gang Milling: Removing material with two or more cutters to increase the production rate.

Aluminum parts

What the Equipment Used in the CNC Milling Process?

Several pieces of equipment must be used in tandem to have a successful CNC milling operation. The equipment that is commonly needed for CNC milling is listed below:

Worktable: The worktable is used to hold the workpiece in place during machining.
Saddle: The saddle is located under the work table. It helps provide additional support and guides the movement of the worktable parallel to the rotating axis of the tool.
Knee: The knee is located under the saddle and helps provide support to both the saddle and worktable. Its position can be adjusted vertically to accommodate different part thicknesses.
Spindle: The spindle is used to hold the cutting tool and directs the translational and rotational movement of the tool.
Arbor: The arbor is a shaft that is assembled through the spindle. Tools are fixed to the arbor.
Ram: The ram is an optional piece of equipment and is usually used in vertical milling or angular milling machines. It is used to help support the spindle.
Machine Tools: Cutting tools such as end mills and other tools are needed for CNC milling.
Interface: The interface is the point at which the operator can communicate with the computer controlling the CNC machine. This will usually consist of a keyboard and display screen, at a minimum.

What Are the Benefits of CNC Milling?

CNC milling has several benefits. For one, CNC machining offers an unprecedented degree of precision for machined parts. This allows tight-tolerance parts to be made both easily and efficiently. Because CNC operations are computer-controlled, little to no human intervention is required. This leads to not just unmatched high production rates, but also the consistent quality and reduced labor costs.

What Are the Limitations of CNC Milling?

Perhaps the biggest limitation of CNC milling is its cost. Even the most basic CNC machines capable of mass production are not cheap, and the machines only get more expensive as they become more advanced. Another limitation of CNC milling is part size and geometry. Part size is limited by the size of the CNC machine. Geometry is limited by the ability of the tool to physically make the desired cut. For example, undercuts, or features that are recessed beneath the outer surface of a part, cannot be cut except with special tools or expensive multi-axis machines. CNC milling is not immune from human error, either. Operators can execute incorrect programs or set up tools incorrectly which leads to bad parts and scrap.

 

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