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Introduction
Here is the most complete and thorough explanation of CNC machining on the internet.
You will learn:
What is CNC Machining?
How CNC Machining is Used –
Parts and Components Made by CNC Machining –
Industrial Uses for CNC Machining –
And much more …
Scroll down to chapter one to begin.
Chapter One: What is CNC Machining?
CNC machining is an electromechanical process that manipulates tools around three to five axes, with high precision and accuracy, cutting away excess material to produce parts and components. The initial designs to be machined by CNC machining are created in CAD, which is then translated into CNC codes to provide programmed instructions to the tools in a CNC machine.
CNC machining produces cutting edge quality on turned components using a wide variety of applications that require vertical and horizontal machining.
The multitasking ability of CNC machines allows for the completion of a component or part in a single operation, with ease and efficiency. The types of applications performed by CNC machines include bushings, collars, fasteners, fittings, inserts, machined components, machined washers, pins, nuts, spacers, spindles, standoffs, drive shafts, and splined shafts to name a few.
Chapter Two: The CNC Machining Process
CNC or Computer Numerical Control machining is a logical and rational process that is planned and designed for the efficient production of parts. The computer controlled machines perform a variety of tasks that have been programmed into the equipment, which begins with creating a two or three dimensional rendering on a computer.
Once the design file is loaded and coded, the machine performs each operation according to the design parameters.
The CNC Machining Process
The difference between CNC machining and other manufacturing processes is that it is a subtractive process that removes layers of material to achieve a particular shape.
Computer Programming
The key to the success of CNC manufacturing is the initial programming. The software must be coded with the proper instructions keeping the machine within its limitations. The processes for CNC equipment are derived from the person who creates its instructions. Care is taken in the development of the programmed instructions to avoid errors and loss of production time.
Computer Aided Design (CAD) and Computer Aided Manufacturing (CAM)
CAD-CAM is a descriptive term for the software used for designing and machining parts and components using a CNC machine. CAD is software used to design, draw, create, and shape parts through the use of geometric shapes and constructs. CAM, on the other hand, takes the information from CAD and translates it into machine language, which is referred to as G-Code.
Before the CAD designed model can be changed into machine language, the CAM software determines the cutting paths for the tools for the removal of the excess material from the workpiece. CAD and CAM work together to provide the CNC machine with the proper and accurate instructions to perform the necessary cutting operations.
CNC Machine Setup
Before the CAD-CAM program can be downloaded into the machine, it has to be set up with the proper cutting tools. There are two methods for completing tool changing. The first method is by pulling tools from the tool cart and placing them in the machine.
The second method is an ATC or automatic tool changer, which has tools stored on a drum or chain. When programmed with the required tools, the ATC removes the old tool and inserts the new one. The purpose of an ATC is to save time and increase efficiency.
An important part of CNC machine setup is the establishment of the gage point, which is how long the tip of the tool is from a point of reference. The proper setting of this part of the process ensures that the tool will cut to the appropriate depth.
One of the final steps in CNC machine setup is the testing of coolant or lubricant. Coolant is delivered by either air, mist, flood, or high pressure. An essential part of checking the coolant is determining the pressure at which it is delivered. The wrong pressure can lead to tool damage, while the wrong amount can damage the machine and equipment.
An unfortunate error made when setting up a CNC machine is failure to check the coolant, which can smell bad, have an insufficient amount, be of low concentration, or may not be appropriately filtered.
Work Holding
The work holding is a device that is used to secure, support, and mount the workpiece. Also referred to as a CNC fixture, it ensures conformity and interchangeability as well as smooth operation. Unlike a jig, the work holding device secures, supports, and stabilizes the workpiece.
Much like the tools used on a CNC machine, work holding fixtures come in several different types, which include turning, milling, drilling, boring, and grinding.
Loading the G-Codes
G-codes have been accepted as the universal language for CNC machining. Though there are standard G-codes for all CNC machines, manufacturers will change G-codes to make them specific to their machines. There is a G-code for every movement of the cutting tools in a CNC machine.
Though various forms of software will create G-codes from a CAD design, they can also be handwritten or conversational, which does not require the use of a CAD design. G-codes can be loaded into the CNC machine using a USB, directly from the CAM computer, or programmed directly into the machine.
Program Proofing
Program proofing is the final step before making the actual cuts. The purpose of proofing is to determine if the program is correct, and that the CNC machine setup is accurate to avoid problems with the g-code.
This process is used to examine if there are any errors in the g-code. Proofing can be accomplished by cutting air, where the machine runs through the cutting process without cutting the workpiece. Cutting air is time consuming and ties up the machine. Another method is g-code simulator, a computer program that simulates the CNC process.
Machining the Part
Once all the preparations have been completed, it is time to insert the workpiece and do the cutting. The first workpiece must be watched carefully as it goes through the CNC process. It is the prototype for all of the parts to follow and will provide data and information regarding the success of the programming.
Execution
After the setup and testing processes are completed, the CNC machine is put into production. CNC machining allows producers to manufacture parts faster, more efficiently, and safely with every part being an exact duplicate of the original design.
Leading Manufacturers and Suppliers
Chapter Three: Types of CNC Machining
A major advantage of CNC machining is the wide array of cuts CNC machines can make. There is a limitless number of shapes, designs, configurations, and images that can be created by the CNC process. Its use enhances the quality of the final part and eliminates errors and flaws from the final product.
Types of CNC Machining
Though CNC machines can be programmed to perform a single function, one of the benefits of CNC machining is their ability to perform multiple operations in a single implementation of the tool. This quality allows producers to insert a single workpiece and have several cuts performed during one machine cycle.
Two types of cuts are male and female. Male cuts are around the outside edges of the workpiece to ensure that the workpiece has the proper dimensions. Female cuts are on the inside of the workpiece. Whether the cuts are male or female, the corners of the cuts are rounded.
Cleanout cuts are similar to female cuts but do not go all the way through the workpiece, while center or online cutting follows the center of the vector shape.
Lathe CNC Machining
Lathe CNC machining turns the workpiece during the cutting operation. The lathe type CNC machine has fewer axes than milling machines, which makes them shorter and more compact.
CNC Milling
Milling is the most common of the CNC machining processes and involves several different types of operations, which include pocketing, facing, slotting, chamfering, and boring. The process of milling uses multiple point cutting tools by feeding the workpiece into the tool in the same direction as the tool is rotating.
Face Milling: Face milling involves cutting surfaces that are perpendicular to the cutter axis of a part. Shell mills or fly cutters are used for this purpose depending on the type of surface that is required.
Pocket Milling: Pocket milling machines away large amounts of material, which saves time and increases the amount of material that is removed.
Slot Milling: Face milling cutters perform slot milling, which is cutting grooves into the workpiece. There are various types of slots, which include closed or open, long or short, straight, deep or shallow, and wide or narrow.
Chamfering Milling: Chamfer milling eliminates sharp edges and leaves a smooth sloped surface.
Boring Milling: Much like the name implies, boring milling enlarges the size of holes using a single cutting point.
CNC Drilling
Drilling in a CNC machine is usually completed with the workpiece being perpendicular to the drill bit. Multiple types of drill bits are used to produce a variety of cylindrical holes. The use of drilling along non-perpendicular axes can be completed on specially designed machines.
CNC Grinding
CNC grinding uses a precision tool that has a rotating wheel to remove material from the workpiece. The grinding process is normally completed at the end of the programmed CNC cycle. The process involves the use of an abrasive wheel to remove burrs at high speed. The grains on the grinder wheel chips away at the work piece to achieve the desired shape.
CNC Turning
Turning CNC processes involve cutting the workpiece as it is being turned. This type of operation is completed on a lathe CNC machine, which feeds the cutting tool along the surface of the workpiece as it rotates removing excess material from the circumference of the rotating piece to reach a specific diameter.
CNC Laser Cutting
CNC laser cutting machines use a laser cutting tool, which can be a gas, crystal, or fiber laser cutter. The difference between the various types is dependent on the working principle of the cutting tool. Unlike other forms of CNC machining, laser cutters do not require the changing of the cutting tool, which makes the process more flexible.
Cutting using a laser cutter is extremely accurate and completed faster than traditional methods. Laser CNC machines are an ideal match for the CNC process since they are completely automated and designed to be programmed.
Plasma CNC Machining
Plasma CNC machines cut by using an electrically conductive material that is accelerated by a stream of heated plasma. The process creates a high powered torch that is capable of cutting through any type of material. The torch on a plasma machine, much like other CNC machines, has its motion programmed by g-codes.
Plasma cutting machines can be table or gantry with table versions having working areas of 1300mm by 2500mm up to ones that are 2000mm by 6000mm. Gantry types have larger working areas that vary between 2 by 6 meters to ones that are 4 by 20 meters.
CNC Router Machine
A CNC router works the same as a lathe or milling machine but is smaller. It is capable of completing all of the functions of a handle held router and is used to shape and form wood products. The reason for using a CNC router to cut wood instead of doing it by hand is the precision and accuracy of the cuts. Standard router bits can be used and materials are cut along the X, Y, and Z axes.
Five Axis CNC Machining
The normal operation of a CNC machine is along the three axes of X, Y, and Z. A five axes machine has two more axes available, which are A and B. The addition of the extra axes makes it easier to cut intricate and complex parts. The increasing use of five axes machines is due to their ability to reduce production time.
The use of a rotating cutting fixture enables the CNC machine to quickly reach the necessary part geometries. Since the table rotates and positions from the five axes, the amount of stress on the cutting tools is decreased, which adds to the life of the CNC machine.
The diagram below is a representation of a five axes CNC machine.
Water Jet CNC Machining
Water jet is a CNC machining process that uses water with an abrasive to remove excess material from the workpiece using water under high pressure. Though water under pressure is capable of cutting various materials on its own, abrasives such as aluminum oxide and garnet may be added to increase the water's cutting ability especially for hard materials.
The water pressure for a water jet cutter is between 20,000 PSI to 55,000 PSI and is delivered through a narrow nozzle.
Chapter Four: CNC Machining Software
CNC machining began with the development of numerical control for the automation of machine tools that used programmable logic for manufacturing processes. From its beginnings as NC in the late 40s and early 50s, it evolved to its present form as computer numerically controlled automation.
The key element in the advancement of CNC machining has been the development of the various software that is used to design parts and create g-code commands for programming CNC machines.
CNC Machining Software
CNC software creates programs to run a machine tool. Every aspect of a CNC machine has its own program. CAD and CAM are the basic programs used by all software producers, who adjust the software to meet the needs of customers and make it more efficient.
Design Software
Autodesk Fusion 360
Autodesk Fusion 360 is a design program platform that includes tools for designing and fabricating. The program has the ability to create complex geometric designs and can simulate their use to determine the amount of force or stress the design can withstand. The three dimensional representations provide an excellent example of what the final part or product will look like.
Solidworks
Solidworks, a design program developed by Dassault Systèmes, uses the parametric based approach to create models and assemblies. The parameters can be numeric or geometric depending on the needs of the design. Aspects of a design can be designated as unchangeable and will not alter if other parts of a design are changed.
AutoCAD
AutoCAD is a manufacturing software that allows users to create, design, modify, and document designs for manufacturing. The program contains hundreds of thousands of symbols for various types of components, which assist in reducing design time. The programming of AutoCAD makes it ideal for easy interface with CNC machines.
Solid Edge
Solid Edge is capable of producing drafting designs and three dimensional representations for product engineering and development. It combines speed with simplicity of design but is flexible and provides direct control of parametric modeling. Solid Edge includes tools for mechanical and electrical designs for manufacturing as well as being able to engineer complex and intricate renderings.
Rhinoceros
Rhinoceros uses geometrical profiles based on a mathematical model that focuses on exacting representations of curves and surfaces. The programming of Rhinoceros allows the user to customize the use of the program by inserting personal commands and menus. It is widely used by several industries.
CAM Software
Once a design is created in CAD, the parameters and features of the design have to be translated into g-code to be downloaded into the CNC machine. This requires CAM software to make the machining workflow easier and efficient.
Things that CAM software does:
Error checking: checks for geometrical errors
Tool path generation: programmed coordinates a tool must follow
Configuration: sets voltage, cutting speed, and depth of cuts
Efficiency: selects the proper orientation for the greatest efficiency
Inventor CAM
Inventor CAM is part of Autodesk that is used to simplify CNC design and programming. Some of its features include a reduction of roughing time, minimization of tool paths, and can program 4 and 5 axes cuts. It includes analysis tools to measure distances and can monitor speed, feed, and machining time.
Fusion 360
Fusion 360 provides a rapid integration between CAD and CAM by having tool paths stored during the design process. The software includes the processes of planning, implementing, and simulation.
Aspire
The main quality of Aspire software is its optimization of tool paths, which allows it to program cuts that have a hand carved appearance. Its various tools calculate the profile cutting path to create gaps that allow for parts to easily fit together.
HSMWorks
HSMWorks is designed to work with Fusion 360, Solidworks, and Inventor. It has a wide array of tools capable of working with any form of cutting tool or device such as water jet, plasma, and laser. It simulates 5 axis cuts and can be used with complex designs that have multi-axis contours. HSMWorks includes a roughing strategy.
SprutCAM
SprutCAM is an adaptable CAM software that can standalone or be connected to the many CAD programs. It supports all of the features of the other CAM softwares such as multi-axis designs and multitasking, which allows for simultaneous operations of multiple tools.
STEP
Step is a file exchange program that is easy to read and has clear text coding. It is extensively used with CAD programs for the transfer of data.
The few cam programs listed here are only a small sampling of available CAM software, which includes EdgeCAM, BodCAD-CAM, CAMWorks, Esprit, GibbsCAM, and HyperMill.
Chapter Five: Materials that CNC Machining is Used to Shape
There is a limitless number of materials that can be shaped by CNC machining. The only limitations are the type of manufacturing process, the shape to be created, and design specifications. The main concern is whether the material is able to withstand the stress and manipulation of a CNC machine.
The type of material determines the cutting tools, cutting speed, feed rate, and how deep the cut will be.
Materials that CNC Machining is Used to Shape
Aluminum
Aluminum has an exceptional strength to weight ratio as well as thermal and electrical conductivity and protection against corrosion. It can easily be machined at low cost and is ideal for creating prototypes.
The variety of aluminum alloys used for CNC machining include:
6061 – is the most commonly used.
6082 – is mostly used in Europe.
7075 – is used in the aerospace industry where there are concerns regarding weight. 7075 can be heat treated to increase its strength and hardness.
5083 – has exceptional strength and resistance to salt water and can be welded.
Stainless Steel
Stainless steel is a widely used metal in the CNC machining process due to its strength, ductility, and wear and corrosion resistance. It can be welded, machined, and polished and can be non-magnetic or magnetic.
Varieties of stainless steel that is used for CNC machining:
304 – is the most common stainless steel used.
316 – is another commonly used stainless steel. Unlike 304, it is resistant to the effects of saltwater.
2205 – has higher strength than other stainless steels and is used in harsh and severe conditions.
303 – has excellent toughness but low corrosion resistance.
630 or 17-4 – is capable of being hardened to 44Rc when heat treated and can withstand extremely high temperatures.
Alloy Steel
Alloy steel is produced using alloys aside from carbon to improve its hardness and toughness as well as its fatigue and wear resistance.
The types of alloy steels used for CNC machining are:
4140 – has excellent mechanical properties but is not suitable for welding.
4340 – unlike 4140, 4340 can be heat treated to increase its hardness and can be welded.
Brass
Brass is a metal alloy with machinability, electrical conductivity, and ideal for low friction applications. It is commonly used in architecture for decorative purposes since it has a pleasing appearance. Brass C36000 is the most common form of brass used in CNC machining due to its tensile strength and corrosion resistance. It is often used for high volume applications.
Polycarbonate
Polycarbonate is a tough thermoplastic that has machinability and extremely high impact resistance. It is transparent, which makes it ideal for fluidic instruments and the glazing of cars. An appealing feature of polycarbonate is its ability to be easily worked and shaped.
Inconel
Inconel alloys have been registered as a trademark brand by Special Metals Corporation for a set of alloyed metals that are nickel and chromium based. It is known for its ability to keep its structural integrity at high temperatures and resistance to oxidation. Inconel alloys are used in harsh and extreme environments. There are several Inconel alloys that include Inconel 625, Chronin 625, Altemp 625, Haynes 625, Nickelvac 625, and Nicrofer 6020.
Thermoplastics
There are a variety of thermoplastics that have sufficient strength and hardness to be shaped by using CNC machining. They are POM, known commercially as Delrin, Teflon or PTFE, and high density polyethylene (HDPE).
POM – has very high machinability and is used for CNC parts that require high precision, stiffness, low friction, and dimensional stability.
Teflon – has chemical and thermal resistance with a low friction coefficient. It is able to withstand temperatures of 200o C and is an excellent insulator flor electrical components .
HDPE – has excellent impact resistance, a high strength to weight ratio, and weathering resistance.
Chapter Six: Swiss Turning and CNC Machining
Swiss CNC machining is a fast and cost effective method for high volume machining of small parts in large quantities. The major feature of Swiss machining is the short cycle times and flexibility in high production applications.
At one time, Swiss machining was viewed as a specialty tool for the making of watches but has developed into a vital tool for the machining of small parts. A unique quality of Swiss machining is the movement of the headstock, which allows for simultaneous rotational and longitudinal movement using radial tool holders. This process allows for rapid forward and backward movement.
What is Swiss CNC Machining?
Swiss CNC Machining developed during the first industrial revolution in the Bienne area of Switzerland. At the time, watchmakers were being pressured to develop smaller and smaller components for watches. Swiss machining developed from the need because the process had the ability to accurately produce smaller diameters.
The main difference between Swiss CNC machining and a traditional lathe is how the headstock moves. In the traditional method, the headstock is fixed in place. With the Swiss Machining Process, the headstock moves the workpiece as it is held by a guiding bushing.
The workpiece is clamped to the headstock and moves through a guide bushing. The workpiece moves in a Z direction as it is tooled. The process allows for the workpiece to be shaped and cut as it moves.
Swiss CNC machining eliminates overhang, which helps in avoiding deflection of the tool from its programmed alignment.
Advantages of Swiss Machining
Accuracy in Machining Small Parts
With traditional machines, the tool is introduced to the workpiece and works around it. In a Swiss machine, the workpiece moves to the tool, which allows for more intricate and complex configurations to be produced at higher speeds and with better tolerances.
Simultaneous Turning and Milling
Simultaneous operations can be performed because the workpiece moves and not the tool. Multiple cuts can be completed in a single cycle.
Cycle Time
A major concern in modern manufacturing is time since customers require their parts produced quickly to meet customer demands. Since Swiss machining completes several cuts in one cycle, there is a substantial reduction in cycle time. This is the result of the workpiece moving and not the tool.
Bar Stock
The major attraction of Swiss machining is its ability to work on smaller bar stock, which is less expensive and reduces the overall cost of the part.
Length to Diameter Ratios
The higher the length to diameter ratio, the less amount of setup time is required. Unlike traditional methods, Swiss machines allow for a higher length to diameter ratio because of how the bar stock is fed into the machine.
Quantities
A major advantage of Swiss machining is the quantities that can be rapidly produced. Essentially, a producer can load bar stock and let the machine run. In the process, it will mill, drill, ream, and saw in one cycle resulting in completed parts ready to ship.
Cost Savings
Since a Swiss machine can complete multiple operations in a single cycle, there is little need for manual labor to change parts or adjust the work piece. This cuts down on labor cost, which reduces the cost of the part.
Precision
The initial reason that Swiss machining was invented was for its ability to produce precision diameter parts accurately and efficiently. This is still true of modern Swiss CNC machining. The dimensional tolerances of Swiss machined parts is ± 0.0001 inches, which is essential for modern market.
Chapter Seven: Industries that Use CNC Machining
The intricacy, accuracy, and precision of CNC machining has made it a valuable part of a wide variety of industry applications and solutions. There is a constant need for the production of precisely engineered parts in the development of modern products. The many innovative advancements in the CNC process has made it essential for the production of many of today’s products from the medical and aerospace fields to the automotive and technological fields.
The greatest need for precision is in industries that produce components that are relied on for their ability to perform in life and death situations, such as the medical field, defense, petrochemical, and aerospace. A failure of a vital part in these fields can place lives at risk. It is for this reason that CNC machining is used to produce and engineer parts and assemblies that will perform in critical situations.
Industries that Use CNC Machining
Medical Industry
Parts produced for the medical industry are customized to fit patient needs. Since many of the components used in the medical field are disposable to protect patients from infections, parts have to be produced with precision and in large quantities. CNC machining has proven to be ideal to meet the demand.
Aerospace
Components produced for the aerospace industry have to endure high speeds, rapid air currents, and high pressure. Every part, piece, and component of an aircraft has to be precisely engineered and designed to meet the demanding conditions. The requirements of the aerospace industry need tolerances of 0.0004 inches. CNC machines meet the demand for high tolerances by machining very durable materials.
Materials for the aerospace industry include titanium, aluminum, nickel, and plastics. The type of materials used depends on how the part will be used and the properties required of the material.
Parts produced for the aerospace industry using CNC machining include:
Manifolds
Bushings
Airfoils
Landing gear parts
Electrical connectors
Antennae
Oil and Gas
The unique nature of parts for the oil and gas industry is how large they must be but still have the precision and dimensional stability of smaller parts. Parts must fit together precisely to avoid any form of failure. Pins, rods, valves, pistons, and drill bits are produced using CNC machining.
The main concern for parts for the oil and gas industry is that they are durable enough to last without the need of frequent replacement. The oil and gas industry requires immediate and speedy turnarounds, which is the reason they rely so heavily on CNC machining for its time saving as well as its accuracy.
Military and Defense
When parts are produced for the military and defense industries, a new level of requirements and stipulations opens since the industry is closely supervised and regulated by government standards. Much like the oil and gas industry, parts and components for the military have to be durable, sturdy, strong, and long lasting. Constant repairs or replacements can lead to delays and risk of lives.
The difficulty of machining parts for the military is the added requirement of secrecy, which is another reason why CNC machining is important. When a part is ordered by the military, there is the necessity of quick and immediate turnaround, which is a major benefit of CNC machining.
Electronics
For the electronics industry, the types of parts required are the opposite of those used by the oil and gas industry and is the reason that CNC machining is a vital part of electronic parts development and production. Most of the parts and components used by the electronics industry are similar to those that motivated the development of Swiss CNC machining. Though accuracy is critical, the main concern is size since much of what is used in electronics is very small but has to be very precise and properly dimensional.
The tight tolerances, small dimensions, and need for precision leave very little room for error when producing parts for electronics. Many of the components have to be micromachined to meet the design requirements.
Marine
As the name implies, the marine industry has the unique requirement of its components being water resistant. Parts may be exposed directly to water or be subjected to high humidity environments. To meet the needs of the marine industry, parts must be produced under special conditions out of materials that meet the exacting requirements.
Another important factor for the marine industry is total portability and the ability to endure the severe conditions found onboard sea going vessels. As with materials for several other industries, parts for the marine industry must be durable since a ship at sea may not be able to easily replace a failed component of part.
Parts produced using CNC machining for seagoing vessels include:
Insulating cases
Propellers
Engine components
Electronic parts
Prototype molds
Boat parts
Firearms
The main concern for the firearms industry is accuracy and precision. The fact that CNC machining allows for in process quality control and monitoring to meet the tight and demanding tolerances is one of the many reasons that firearm components are produced using CNC machining. A special feature for the firearm industry is the ability of CNC machines to record and log the serial numbers of the items being produced, which are engraved on the piece. This allows for easy tracking and cataloging.
Optics
The challenge of the optics industry is the machining of complex geometries. The benefit of CNC machining is its flexibility as well as its ability to produce cuts on 5 axes for light weight materials. Optic components have high aspect ratios with specialty bevels, the need for precision cut holes and inserts, and accurately placed mounting surfaces.
In many cases, for the optics industry, ultrasonic CNC machines are used for their accuracy and precision.
Telecommunications
The accuracy, dependability, and high tolerances of CNC machining are critical to the telecommunications industry since failure can have severe ramifications. The first and most vital factor for telecommunications parts is durability and indestructibility since a breakdown or error can create insurmountable and critical difficulties.
CNC machining is ideal for telecommunication requirements because of the high tolerances and exceptional reliability. Much like the optics industry, the geometries for the telecommunications industry can be complex and complicated presenting engineering and design challenges. Typical materials are aluminum, stainless steel, and brass.
Automotive
Of the many industries that use CNC machining, the automotive industry has the greatest need and makes the most use of the efficiency and excellent turnaround times for CNC machined parts. The auto industry is constantly seeking better and more efficient methods for producing components and parts. It has been the leader in developing technological advanced methods, which is the reason that it was one of the first industries to make extensive use of CNC machining.
The main features of CNC machining that have become the hallmark of the auto industry are speed of production, automation, accurate repeatability, precision, and ease of customization. Interior panels, starter motors, cylinder heads, gearboxes, and drive axles are quickly and efficiently produced to meet production needs and specifications.
Chapter 8: CNC Terminology
As with any computer programming, CNC machining has its own computer language regarding programming, actions, and movements. Although there are different forms of codes for programming CNC machining, G-codes are the primary codes that tell the tools of a CNC machine what movements and processes to perform. The CNC machine translates computer-aided design (CAD) instructions into G-codes.
There are endless CNC terms with proprietary terms used by manufacturers. However, as with G-codes, certain CNC terms apply to all CNC users and are understood across all industries.
5-Axis CNC Machining
The term 5-axis refers to the number of axes available on a CNC machine. The initial axes of a CNC machine are the X-axis, Y-axis, and Z-axis, which are axes located along the bed of a CNC machine. Two of the initial three axes have additional motion modes that allow them to perform complex and intricate motions, such as rotations.
Address
The command block of a CNC machine is controlled by letter address commands. The definition of the letter address commands changes in accordance with the G-code that appears in the command block. Letter address commands include all of the letters of the alphabet, with each letter designating a function, such as T standing for tool selection and L standing for fixed cycle loop count.
Automatic Tool Changer (ATC)
The main benefit of CNC machines is their ability to perform complex and intricate cutting operations without human interference. The ATC changes tools on a CNC machine to fit the task being performed and is controlled by G-code commands.
Axis
The axis refers to the plane of motion of a CNC cutting tool. The predominant axes are the X, Y-axis, and Z axes, with the B and C axes added for additional motions.
Bed
The bed supports a CNC machine and is where the workpiece is placed for machining. As with spindles, beds can be fixed or mobile, with the fixed bed remaining in place as the spindle moves while the mobile bed moves as the spindle remains stationary. Beds for CNC machines vary per the machine's manufacturer and the needs of the part to be produced.
CAD (Computer Aided Design)
CAD is a design software that assists engineers in creating renderings of their designs. The designs produced in CAD can be downloaded into a CNC machine and changed to G-codes for production.
G-Codes and M-Codes
G and M codes are the main contents of CNC programming, with G-codes being preparatory codes that prepare the machine for a specific motion. M-codes are miscellaneous words that control auxiliary options. Each block of code can have only one M-code.
Although CNC machines come with pre-programmed M and G codes, they are flexible enough that manufacturers can add proprietary codes for special functions and operations.
Gantry
The gantry straddles the cutting bed, moves along the x-axis, and carries the spindle. The two versions of gantries are fixed and moving, where a fixed gantry does not move while a moving gantry moves along the cutting table.
Home Position
The home position is the reference point for the X, Y, and Z-axes and is set by a G-code.
Jig
A jig is a tool used to hold and control the location of a workpiece and keep it in the proper position for cutting tools. For example, a jig will guide a cutting tool through a specific operation during milling.
Kerf
The kerf is the width of the cut into the workpiece.
N Codes
N codes identify a line of code and are followed by a number that identifies a block of code and its line number. When entered into a CNC machine, N codes will progress in increments of five or ten to leave space and provide programming flexibility.
Nesting
Nesting is laying out the cutting pattern to limit the amount of waste. The nesting process takes the original cutting pattern and reorients it to reduce waste.
Part Program
The part program contains all of the instructions regarding a part and is the set of commands that initiates the cutting, shaping, and other CNC functions.
Post Processor
A post-processor, or post, translates the computer language or image of CAD into a language that a CNC machine can understand. In nearly all cases, the CNC language is G-codes.
Resolution
The resolution of a CNC machine is how accurately the machine determines its position and how precisely the axes follow the letter address command codes.
Revolutions Per Minute (RPM)
In CNC machining, RPM refers to the rate per minute that the spindle will spin.
Special Characters
Keys from a computer keyboard are also used as code designations. For example, the percent sign (%) indicates a program's beginning or end. The backward slash (/) is a code for block delete. Semicolons, parentheses, and dashes are codes or commands placed in blocks of command codes.
Spindle
The spindle is at the heart of a CNC machine. It is a rotating assembly with a taper for tool holders. A spindle is powered by a motor, which varies depending on the manufacturer of the CNC machine.
Step Down and Stepover
The step down is the distance the Z-axis tool cuts into the workpiece, while the stepover is the distance a tool moves away from a cutting path to a new cutting path.
Vector
Vector files are 2D graphics that include shapes, lines, coordinates, sizes, and colors. They are mathematical equations used to establish points on a Cartesian plane, which makes them easy to rescale. Each vector type has its advantages and quality depending on its software.
Conclusion
CNC machining is an electromechanical process that manipulates tools around three to five axes, with high precision and accuracy, cutting away excess material to produce parts and components.
The multitasking ability of CNC machines allows for the completion of a component or part in a single operation, with ease and efficiency.
CNC or Computer Numerical Control machining is a logical and rational process that is planned and designed for the efficient production of parts.
A major advantage of CNC machining is the wide array of cuts CNC machines can make
CNC software creates programs to run a machine tool. Every aspect of a CNC machine has its own program.
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