Modern manufacturing industries have introduced some advanced machining processes, including laser cutting, EDM wire cutting, plasma cutting, etc. CNC machines sometimes categorized as a type of machining operation, and the following are some advanced machining operations commonly applied in modernized CNC machining industries.
Thermal cutting
Thermal
cutting is a process that uses heat to cut or shape materials. It involves
applying intense heat to melt or vaporize the material, allowing for precise
cutting or shaping. Various industries, including metal fabrication, automotive
manufacturing, and construction, widely use thermal cutting methods for cutting
materials such as steel, aluminum, and other metals. The choice of the specific
thermal cutting method depends on factors like material type, thickness,
desired cutting speed, and accuracy requirements. The group of thermal cutting
methods includes:
- Laser cutting
- Plasma cutting
- Oxy-fuel cutting
Laser cutting
Laser
cutting is a CNC cutting process that utilizes a high-powered laser to cut
materials. This technology involves the creation of a high-density light beam by
stimulating lasing material with an electrical discharge within a confined
container. The laser beam vaporizes materials, resulting in a clean-cut edge.
Although commonly used in industrial manufacturing, laser cutting is a thermal
separation process where the laser beam heats the material intensely, causing
it to melt or vaporize. Laser cutters are capable of cutting various materials,
including metals, MDF, wood, acrylic, and more. There are three main types of
laser cutters:
- CO2 Laser Cutter
- Crystal Laser Cutter
- Fiber Laser Cutter
CO2 Laser Cutter: The CO2 laser cutter produces light by passing electricity through a gas-filled tube, typically containing a mixture of carbon dioxide, nitrogen, hydrogen, and helium. The tube has mirrors at both ends, with one mirror fully reflecting the light and the other permitting some light to pass through. These mirrors guide the laser beam toward the target material for cutting. CO₂ laser cutting is capable of cutting contours in metal sheets like steel, stainless steel, and aluminum. It offers exceptional accuracy and grants substantial flexibility in shaping, including the ability to cut complex shapes.
Crystal Laser Cutter: A crystal-powered laser utilizes beams generated from neodymium-doped garnet or vanadium. These lasers emit a powerful beam capable of cutting through thicker or harder materials compared to other types of laser cutters. The laser cutter itself consists of a laser resonator, which contains either a gas mixture or a crystal body or glass fibers, depending on the cutting method. The cutting process begins by applying energy to the mixture, which is then directed through various mirror lenses to focus the laser. Crystal laser cutters employ a combination of crystals, such as neodymium-doped yttrium orthovanadate and neodymium-doped yttrium aluminum garnet, to generate these powerful beams. They are well-suited for cutting strong and thick materials due to the high intensity of their beams.
Fiber Laser Cutter: Fiber laser technology generates a focused, high-powered laser beam through stimulated radiation. Laser diodes emit light that is transmitted through fiber-optic cables for amplification. When this intense laser beam interacts with a material surface, it absorbs the high-intensity light and converts it into heat, melting the surface. Fiber lasers utilize pump light from laser diodes, which emit light sent through the fiber-optic cable. Optical components within the cable generate and amplify specific wavelengths. Finally, the resulting laser beam is shaped and emitted.
Oxy-fuel cutting
Oxy-fuel cutting is a combustion process that uses oxygen or a fuel gas flame. The heating flame warms up the material to its ignition temperature. Then, an oxygen jet with at least 99.5 percent purity is blown onto the heated spot, oxidizing the metal. The burning metal immediately turns into liquid iron oxide. This method involves using a fuel gas, such as acetylene, and oxygen to create a high-temperature flame that melts the material. A stream of oxygen is directed onto the heated area, causing the material to react with the oxygen and form metal oxides, which are then blown away by the gas stream. Cutters commonly use four basic fuel gases in combination with oxygen for this process: acetylene, propane, propylene, and natural gas.
Plasma cutting, also known as plasma arc cutting, is a melting process where a jet of ionized gas at temperatures above 20,000°C is used to melt and expel material from the cut. During the process, an electric arc is struck between an electrode (cathode) and the workpiece (anode). The electrode is recessed in a water- or air-cooled gas nozzle, which constricts the arc and forms a narrow, high-temperature, high-velocity plasma jet. Plasma cutting utilizes a jet of ionized gas, called plasma, to cut through electrically conductive materials. An electrical arc is created between an electrode and the workpiece, ionizing the gas and forming a plasma. The plasma's high temperature melts the material, while the gas stream blows away the molten metal. Plasma gases usually used are argon, argon/hydrogen, or nitrogen.
Water jet cutting
Cutting
with a water jet is an engineering method that utilizes the energy from
high-speed, high-density, ultra-high-pressure water to cut objects. It involves
using a high-pressure stream of water, often mixed with abrasive particles like
garnet or aluminum oxide, to enhance its cutting ability. The process entails
firing highly pressurized water through a ruby or diamond nozzle into a mixing
chamber. This pressure creates a vacuum and draws garnet sand into the stream,
which is then directed at the object to be cut. The resulting water jet,
propelled at pressures ranging from 30,000 to 90,000 pounds per square inch
(psi), can slice through materials with precision and accuracy. Cutting with a
water jet can be classified into two types based on cutting capacity.
Water
Jet Cutting: This type of cutting utilizes a water jet only and is not suitable
for cutting hard materials, but effective for cutting soft materials such as
wood, plastic, and rubber.
Abrasive
Jet Cutting: The type of cutting incorporates jet propulsion and uses abrasive
materials mixed into the water jet to increase cutting power. By mixing
abrasive materials, it becomes possible to cut hard and laminated materials,
including titanium, stainless steel, and aluminum.
Electric Discharge Machining (EDM)
Electrical Discharge
Machining (EDM), also known as spark machining, spark eroding, or wire erosion,
is a non-traditional machining process used for shaping and cutting conductive
materials with high precision. The principle behind EDM is based on the erosion
of the material through repetitive sparks between the workpiece and the tool,
which are submerged in a bath of the dielectric medium. It is particularly
effective for working with materials that are difficult to machine using
conventional methods, such as hardened steels and titanium.
In EDM, an electrically conductive workpiece and a specially designed tool called an electrode, are immersed in a dielectric fluid. The workpiece and electrode are connected to a power supply. The process involves the controlled generation of electrical discharges or sparks between the electrode and the workpiece. When voltage is applied, a spark jumps across the small gap between the electrode and the workpiece, resulting in rapid localized heating. The intense heat melts and vaporizes small particles of the workpiece material, which are then flushed away by the dielectric fluid. By precisely controlling the voltage, current, and spark duration, EDM can selectively remove material from the workpiece, creating complex shapes and intricate details. Electric discharge machining can be categorized into three common types:
- SInker ED
- Wire EDM
- Hole-drilling EDM.
Sinker EDM: In sinker EDM,
the electrode and workpiece are brought close together, and sparks occur as the
electrode is submerged and moved in and out of the workpiece, creating cavities
or molds. For sinker discharge machining, precise copper and/or graphite
electrodes are first machined to the desired cavity shape and then used to
erode the shape into hard materials.
Wire EDM: Wire cut EDM uses
a wire as the "cutter" and erodes material by sparking between the
wire and the workpiece. The wire electrode discharges along the entire length
of the cut and feeds through, aiding in the removal of cuttings. It utilizes a
thin, electrically conductive wire that is continuously fed through the
workpiece, cutting it into desired shapes or contours.
Hole drilling EDM: Similar
to sinker EDM, hole drilling with electrical discharge machining uses electric
current carried to the workpiece through a pipe-shaped electrode to erode or
burn away conductive materials. The electrode never touches the material being
machined, minimizing the deflection of the pipe electrode compared to drilling
holes with a traditional cutting tool.
3D printing
3D
printing, also known as additive manufacturing, creates three-dimensional
objects layer by layer using a computer-generated design. It enables the
production of complex and customized objects without the need for traditional
manufacturing methods like cutting, molding, or subtracting material.
The
process starts with creating a 3D model using computer-aided design (CAD)
software or obtaining an existing model. The 3D model is then sliced into thin
cross-sectional layers using slicing software. Each layer represents a 2D
representation of the object and contains the necessary information for the
printer to create that specific layer.
After
slicing, the printer is prepared for the printing process, and the appropriate
material, such as plastic, metal, or resin, is selected based on the desired
properties of the final object.
Finally,
the sliced layers are sent to the 3D printer, which utilizes various techniques
to create the object. The most common methods used are:
- Fused Deposition Modeling (FDM)
- Stereolithography (SLA)
- Selective Laser Sintering (SLS)
Fused Deposition Modeling (FDM), also known as Fused Filament Fabrication (FFF), is the most commonly used method of 3D printing. FDM/FFF 3D printing works by melting a thermoplastic filament and extruding it through a heated nozzle. The nozzle then deposits the material layer by layer, creating a three-dimensional object. An FDM 3D printer operates by progressively adding layers of melted filament material onto a build platform until a finished part is achieved. FDM relies on digital design files that are uploaded to the machine and translated into physical dimensions. Materials suitable for FDM include ABS, PLA, PETG, and PEI, which are fed as threads through the heated nozzle.
Stereolithography
(SLA) is an additive manufacturing process that utilizes 3D printing
technology. In this process, a liquid photopolymer resin serves as the printing
material. The procedure starts with a resin-filled tank, while a build platform
is positioned just above the surface of the liquid resin. A computer-controlled
ultraviolet (UV) laser beam is employed to selectively solidify or polymerize
the resin, following the precise pattern dictated by the digital design of the
object. As the UV laser beam scans the liquid resin's surface, it solidifies
the material layer by layer. Once a layer is completed, the build platform is
slightly lowered, and a fresh layer of liquid resin is spread over the previous
one. The laser then scans the new layer, solidifying and bonding it to the
layer beneath. This iterative process continues until the entire object is
created.
Selective Laser Sintering
(SLS) is an additive manufacturing technology used to create 3D objects by
selectively fusing powdered materials together using a high-powered laser beam.
The SLS process begins with a thin layer of powdered material, usually plastic,
metal, or ceramic, spread across a construction platform. A laser beam is then
directed at specific points within the powder bed, heating and fusing the
particles together based on a digital 3D model of the required object. The
laser selectively sinters the powder, solidifying it and creating a solid
cross-section of the object. Once a layer is complete, a new layer of powder is
spread over the previous one, and the process is repeated. This layer-by-layer
approach continues until the entire object is formed within the powder bed.
CNC Routing
The
CNC router is a machine tool equipped with a rotating cutting tool known as a
router bit. This bit spins at high speeds and cuts into the material based on
programmed instructions, removing excess material and creating the desired
shape or pattern. CNC routing finds common use in woodworking, metalworking,
plastic fabrication, and composite manufacturing industries. The process
commences with the creation of a digital design or CAD (computer-aided design)
file that outlines the desired dimensions, shapes, and patterns. Subsequently,
this file is converted into machine-readable code, typically through the use of
CAM (computer-aided manufacturing) software. The CNC router then reads and
translates the code into precise movements of the cutting tool. CNC routers are
capable of various operations, including cutting, drilling, milling, engraving,
and 3D carving. They facilitate the replication of complex designs and
intricate details with ease. Additionally, CNC routing machines can handle a
wide range of materials, including wood, plastic, foam, metals, and composites.
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