Computer Numerical Control (CNC) CNC Training Course Computer numerically controlled (CNC) 03035530865 Course in Rawalpindi What is CNC Machining? CNC machining is a term commonly used in manufacturing and industrial applications, but exactly what does the acronym CNC stand for and what is a CNC machine? The term CNC stands for 'computer numerical control', and the CNC machining definition is that it is a subtractive manufacturing process which typically employs computerized controls and machine tools to remove layers of material from a stock piece—known as the blank or workpiece—and produces a
custom-designed part. This process is suitable for a wide range
of materials, including metals, plastics, wood, glass, foam,
and composites, and finds application in a variety of
industries, such as large CNC machining and CNC machining
aerospace parts. When speaking in terms of the machine itself,
the CNC machine definition is that it represents the actual
programmable machine that is capable of autonomously performing
the operations of CNC machining. Note the contrast between the
process (CNC machining definition) versus the machine (CNC
machine definition).
Subtractive manufacturing processes, such as CNC machining, are
often presented in contrast to additive manufacturing
processes, such as 3D printing, or formative manufacturing
processes, such as liquid injection molding. While subtractive
processes remove layers of material from the workpiece to
produce custom shapes and designs, additive processes assemble
layers of material to produce the desired form and formative
processes deform and displace stock material into the desired
shape. The automated nature of CNC machining enables the
production of high precision and high accuracy, simple parts
and the cost-effectiveness when fulfilling one-off and medium-
volume production runs. However, while CNC machining
demonstrates certain advantages over other manufacturing
processes, the degree of complexity and intricacy attainable
for part design and the cost-effectiveness of producing complex
parts is limited.
While each type of manufacturing process has its advantages and
disadvantages, this article focuses on the CNC machining
process, outlining the basics of the process, and the various
components and tooling of the CNC machine (sometimes
incorrectly known as a C and C machine). Additionally, this
article explores various mechanical CNC machining operations
and presents alternatives to the CNC machining process.
Overview of CNC Machining Process
Evolving from the numerical control (NC) machining process
which utilized punched tape cards, CNC machining is a
manufacturing process which utilizes computerized controls to
operate and manipulate machine and cutting tools to shape stock
material—e.g., metal, plastic, wood, foam, composite, etc.—into
custom parts and designs. While the CNC machining process
offers various capabilities and operations, the fundamental
principles of the process remain largely the same throughout
all of them. The basic CNC machining process includes the
following stages:
Designing the CAD model
Converting the CAD file to a CNC program
Preparing the CNC machine
Executing the machining operation
CAD Model Design
The CNC machining process begins with the creation of a 2D
vector or 3D solid part CAD design either in-house or by a
CAD/CAM design service company. Computer-aided design (CAD)
software allows designers and manufacturers to produce a model
or rendering of their parts and products along with the
necessary technical specifications, such as dimensions and
geometries, for producing the part or product.
Designs for CNC machined parts are restricted by the
capabilities (or inabilities) of the CNC machine and tooling.
For example, most CNC machine tooling is cylindrical therefore
the part geometries possible via the CNC machining process are
limited as the tooling creates curved corner sections.
Additionally, the properties of the material being machined,
tooling design, and workholding capabilities of the machine
further restrict the design possibilities, such as the minimum
part thicknesses, maximum part size, and inclusion and
complexity of internal cavities and features.
Once the CAD design is completed, the designer exports it to a
CNC-compatible file format, such as STEP or IGES.
CAD File Conversion
The formatted CAD design file runs through a program, typically
computer-aided manufacturing (CAM) software, to extract the
part geometry and generates the digital programming code which
will control the CNC machine and manipulate the tooling to
produce the custom-designed part.
CNC machines used several programming languages, including G-
code and M-code. The most well-known of the CNC programming
languages, general or geometric code, referred to as G-code,
controls when, where, and how the machine tools move—e.g., when
to turn on or off, how fast to travel to a particular location,
what paths to take, etc.—across the workpiece. Miscellaneous
function code, referred to as M-code, controls the auxiliary
functions of the machine, such as automating the removal and
replacement of the machine cover at the start and end of
production, respectively.
Once the CNC program is generated, the operator loads it to the
CNC machine.
Machine Setup
Before the operator runs the CNC program, they must prepare the
CNC machine for operation. These preparations include affixing
the workpiece directly into the machine, onto machinery
spindles, or into machine vises or similar workholding devices,
and attaching the required tooling, such as drill bits and end
mills, to the proper machine components.
Once the machine is fully set up, the operator can run the CNC
program.
Machining Operation Execution
The CNC program acts as instructions for the CNC machine; it
submits machine commands dictating the tooling’s actions and
movements to the machine’s integrated computer, which operates
and manipulates the machine tooling. Initiating the program
prompts the CNC machine to begin the CNC machining process, and
the program guides the machine throughout the process as it
executes the necessary machine operations to produce a custom-
designed part or product.
CNC machining processes can be performed in-house—if the
company invests in obtaining and maintaining their own CNC
equipment—or out-sourced to dedicated CNC machining service
providers.
Types of CNC Machining Operations
CNC machining is a manufacturing process suitable for a wide
variety of industries, including automotive, aerospace,
construction, and agriculture, and able to produce a range of
products, such as automobile frames, surgical equipment,
airplane engines, and hand and garden tools. The process
encompasses several different computer-controlled machining
operations—including mechanical, chemical, electrical, and
thermal processes—which remove the necessary material from the
workpiece to produce a custom-designed part or product. While
chemical, electrical, and thermal machining processes are
covered in a later section, this section explores some of the
most common mechanical CNC machining operations including:
Drilling
Milling
Turning
CNC Drilling
CNC Milling
Milling is a machining process which employs rotating multi-
point cutting tools to remove material from the workpiece. In
CNC milling, the CNC machine typically feeds the workpiece to
the cutting tool in the same direction as the cutting tool’s
rotation, whereas in manual milling the machine feeds the
workpiece in the opposite direction to the cutting tool’s
rotation. Operational capabilities of the milling process
include face milling—cutting shallow, flat surfaces and flat-
bottomed cavities into the workpiece—and peripheral milling—
cutting deep cavities, such as slots and threads, into the
workpiece.
CNC Machining Equipment and Components
As indicated above, there is a wide range of machining
operations available. Depending on the machining operation
being performed, the CNC machining process employs a variety of
software applications, machines, and machine tools to produce
the desired shape or design.
Types of CNC Machining Support Software
The CNC machining process employs software applications to
ensure the optimization, precision, and accuracy of the
custom-designed part or product. Software applications used
include:
CAD
CAM
CAE
Course Contents
Basic Math & Trigonometry
Tolerances
Safety & First Aid
Fundamentals of CAD
Conventional Machine Shop Operations
CNC Machine Shop Operations
Manual Programming
CNC Software Programming (CAM)
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