You probably have some idea of how lathes and other metalworking machines work. As technology and computers have improved over the years, a new high-precision computer-controlled manufacturing technique called CNC machining has spawned. CNC machines, or computer numerically controlled machines, are electromechanical devices that can manipulate tools around various axis, usually three or five, with high precision per instruction from a computer program. CNC machining is one of two ways that engineers, machinists, or makers can generate a physical part from a computer design file. The other is 3D printing, also known as additive manufacturing. Like other traditional machining processes, CNC machining is a subtractive process where the material is removed from stock.
History of CNC Machines
The first CNC machines were developed in the 1940s and 50s and relied primarily on a data storage technique known as punched tape. The code to control the machines would be manually punched into a data card and fed into a system that would interpret the data. These early machines were rudimentary, and their functionality was limited. Modern CNC machining technologies rapidly grew as technological capability only accelerated in the late 20th century, which brings us to how modern CNC machines work. As mentioned before, machining is a way to transform a stock piece of material such as aluminum, steel, or titanium into a finished product or part. Before modern computer-aided manufacturing and computer-aided design programs such as Autodesk were around, CNC machines relied on digital instructions specifically referred to as “g code.”
Machinists would manually write the G code to control these machines. When you compare the capabilities of automated CNC machining to manual alternatives like lathes and other machining techniques, you can start to see the benefits. CNC machines run faster, with higher precision and accuracy, while transforming a digital design into a physical part. CNC machines are precise and are measured in thousandths of an inch, referred to as standards. CNC machining can provide tolerances on parts of around +/-0.005 inches. Fine CNC machining can produce tolerances of about +/-0.001 inches in specialized processes like polishing, which can offer up repeatable tolerances as tight as +/-0.00005 inches. For reference, human hair is 0.0069 inches thick.
Types of CNC machines
CNC Milling Machine
CNC mills use rotary cutters to remove material by advancing a cutter into a workpiece. The most basic CNC mills have an X, Y, and Z system, and they run programs that follow letter- and number-based prompts that instruct pieces to move specific distances. A mill’s functions include face milling, tapping, drilling, turning, and shoulder milling.
Lathes (CNC Turning Machine)
Lathes produce precise, high-velocity circular cuts. Lathes are commonly used for complex designs that would be impossible to achieve with a manual machine. The majority of CNC lathes have two axes, X and Z. Some models have more than two axes, allowing them to perform more complex tasks. The material is held on a rotating spindle on a lathe. The non-rotating cutting tool or drill forms the geometry or shape of the part by tracing its perimeters.
Plasma Cutting Machines
A plasma torch is used to cut the material. Plasma cutters are primarily used for metal materials, and they can also be used on other materials. The machine generates heat and speed using compressed air gas and electrical arcs.
Electric Discharge Machines(EDM)
Electrical sparks are used to cut and shape two workpieces using electrodes. As the gap between these electrodes closes, a current flows through, removing a portion of the workpiece. This technique is also known as die sinking, spark machining, spark eroding, burning, or wire erosion. Wire EDM and Sinker EDM are two subtypes.
Water Jet Cutting Machines
Hard materials, such as metal or stone, are cut with high-pressure water jets. Water jets are frequently used when the material cannot withstand high temperatures.
There are some other tools and machines with CNC variants:
CNC routers, 3D printing machine, induction hardening machines, surface grinders, milling machines.
How CNC Machine Works
Now that we have the basics of CNC machining, we can start to dig into the intricacies held within many designs or specific machining processes that require the use of multiple tools to make cuts. A machinist will often build digital tool libraries that interface with the physical CNC machine. These machines, often costing hundreds of thousands of dollars, can automatically switch tooling when directed by their digital instructions, allowing them to become manufacturing workhorses. Basic CNC machining will move one or two axis, referred to as the X-axis and the Y-axis. You’ll often hear the terms “2.5 axis,” “3 axis,” and “5 axis.” A machine can make cuts in three axis, which refers to the degrees of freedom. A machine can make cuts in a 3-axis machine that will move in the X, Y, and z axis.
In contrast, a 5-axis machine can move in these three axis along with two additional rotational axis, as you might be able to imagine the possibilities of production. Five-axis machines are practically endless. Five-axis machines used to be relegated to high-precision work, but as they have become more affordable, they have quickly become standard in many shops. The first is drills. They work by spinning a drill bit and moving a bit into contact with a stationary stock. Next, we have lathes that function like drilling lathes, spinning the block of material against a stationary drill bit or cutter to remove material in a circular or fluid path. The shape capabilities of lathes are more limited than other techniques, but modern technology does allow these machines to create things such as square holes or non-circular shapes. Lastly, the most common CNC machine type is a milling machine. Milling machines use rotary cutting tools to remove material from a stock piece. The function is similar to drills, with their tooling capabilities encompassing much more variety. Almost any material can be used in CNC machines. Different materials have different properties, so machinists and engineers will overcome their unique challenges by altering machining variables like tool selection, rpm feed rate, and coolant flow, among a wide variety of other factors. CNC machined parts are all around you. They hold together and perform vital functions aboard.
CNC machining is arguably the most critical manufacturing process of the 21st century. Its functionality drives technological advancement across the globe. It’s a trend keeping up with the growth of technology, and machinists across the planet are changing the world with their CNC machining skills.
In general, CNC machining can be simplified into a 3-step process.
- CAD file is designed
- A CNC technician translates the CAD file into the CNC program
- The CNC program is initiated and the part is machined
Benefits of CNC Machining
CNC machining is suited for applications that require production-grade materials and rapid prototyping of precise plastic and metal parts with excellent surface finishes. CNC machining’s repeatability also enables low-volume manufacture of items. Benefits of CNC machining:
- High-Precision Parts
- Large, Scalable Volumes
- Variety of Shapes, Sizes & Surface Finishes
- Fast Turnaround
- Lower Costs with Greater Efficiencies
Considerations of CNC Machining
Workholding
A part’s geometry will dictate how it will be positioned on the CNC machine and the amount of setup required. If a part is manually repositioned, it can result in a small positional error and impact the cost of the project and part accuracy.
Machine Tool Stiffness
The tool used to cut the part may vibrate while operating. Tool stiffness may result in loose tolerances.
Workpiece Stiffness
Temperatures and cutting forces developed during machining may cause the workpiece to vibrate or even cause deformities. The part must have a minimum wall thickness and a maximum aspect ratio of tall features to prevent workpiece stiffness.
Tool Geometry
CNC machining cutting tools have a cylindrical shape and a flat or rounded end. Tool geometry can restrict the CNC machined parts geometries. The inside vertical corners of the part produced will have a radius, even if a small cutting tool is used.
Workpiece Shape(Geometry Complexibility)
If the cutting tool is unable to reach a surface, it cannot be CNC machined. This limitation on parts requiring hidden internal geometries limits a workpiece’s maximum machining depth.
CNC Machining Materials
CNC machining provides a wide range of materials for CNC prototypes and production components, ranging from solid metals such as stainless steel and titanium to soft metals such as aluminum, copper, and brass, and plastics such as ABS, PC, and PA and more.
CNC Metal Material
Alloy steel contains trace amounts of one or more alloying elements (other than carbon), such as manganese, silicon, nickel, titanium, copper, chromium, and aluminum. Alloying provides it with unique qualities not present in standard carbon steel. Due to its low cost, wide availability, ease of processing, and superior mechanical rates, alloy steel is ideal for industrial applications. In general, alloy steels are more malleable to heat and mechanical treatment than carbon steels.
LEADRP offers a complete Alloy Steel CNC machining service and can produce custom Alloy Steel parts in various shapes and grades, including 4130, 4140, 4340, and more.
Mild steel is a type of carbon steel with a low amount of carbon. It is also known as “low carbon steel.” Low carbon means it has very little carbon and other alloying elements to block dislocations in its crystal structure, resulting in less tensile strength than high carbon and alloy steels. Mild steel has good weldability and machinability, making it a popular choice for consumer products.
LEADRP offers a complete Mild Steel CNC machining service and can produce custom Mild Steel parts in a variety of shapes and grades, including Hot and Cold Rolled, Commercial Quality, Galvanized, 1018, 1020, 1026, 1020/1026, CR 1045, HR 1045, 12L14, CR 1215 and more.
Tool steel is a type of carbon alloy steel. It is frequently used to create, modify, or repair hand tools and machine dies. Tool steel is notable for its hardness, abrasion, and deformation resistance. Because steel can retain a cutting edge at extremely high temperatures, it is frequently used to shape other materials via cutting, pressing, coining, or extruding. Because of their abrasion resistance, they are commonly used in the production of injection molds. Tool steel is widely used in dies (stamping or extrusion), cutting, mold production, and impact applications such as hammers (personal or industrial).
LEADRP offers a complete Tool Steel CNC machining service and can produce custom Tool Steel parts in various shapes and grades, including A2, D2 and O1, and more.
Stainless steel is a steel alloy that is more corrosion resistant than carbon/alloy steel. Stainless steel is an iron alloy that contains at least 10.5 percent chromium. The presence of chromium results in forming a thin chromium oxide film on the surface of the steel, known as a passivation layer. This layer prevents corrosion on the steel surface; the higher the Chromium concentration in the steel, the more excellent the corrosion resistance. Stainless steel is an ideal material for food handling/processing, medical instruments, hardware, appliances, and structural/architectural products.
LEADRP offers a complete Stainless Steel CNC machining service and can produce custom Stainless Steel parts in various shapes and grades, including 17-4, 303, 304, 316, 416, 440C, and more.
Copper alloys are one of the most versatile metals, and they have beneficial properties like corrosion resistance, high thermal conductivity, and very high electrical conductivity. Copper alloys are excellent for different industries such as electrical, construction, transport, and consumer goods. The final product made from copper includes architectural parts, coinage, condenser/heat exchangers, plumbing, radiator cores, musical instruments, locks, fasteners, hinges, ammunition components, and electrical connectors.
LEADRP offers a complete Copper CNC machining service and can produce custom Copper parts in a variety of shapes and grades, including Copper C110 and C101.
Brass is a mixture of copper and zinc. Small amounts of zinc elements are frequently added to improve specific properties. Depending on the part of zinc added to the alloy, the color of brass can range from red to yellow. Alloying can increase strength, hardness, electrical and thermal conductivity, corrosion resistance, and color. Brass is also germicidal, which means it can kill microorganisms when they contact it.
Brass is used in various applications and products, including decorative items, architectural parts, condenser/heat exchangers, plumbing, radiator cores, musical instruments, locks, fasteners, hinges, ammunition components, and electrical connectors.
LEADRP offers a complete Brass CNC machining service and can produce custom Brass parts in various shapes and grades, including Brass C260 and C360.
Aluminum is a silver-colored, low-density metal used in a wide range of commercial applications. Under most conditions, unalloyed aluminum is ductile, has moderate strength, and is highly corrosion-resistant. Appropriate alloying elements (Cu, Mg, Mn, Si, etc.) and subsequent heat/work treatments can significantly strengthen aluminum. Because of its low density and corrosion resistance is widely used in aerospace, transportation, architectural, food, and chemical handling (cookware, pressure vessels, etc.) industries.
LEADRP offers a complete Aluminum CNC machining service and can produce custom Aluminum parts in a variety of shapes and grades, including 1100, 2011, 2024, 3003, 4017, 5052, 6061, 6063, and 7075.
Titanium alloys are alloys composed of titanium and other chemical elements. Titanium alloys are light in weight, have incredibly high tensile strength and toughness, are extremely corrosion resistant, and withstand extreme temperatures.
Titanium alloys are widely used in military applications, aircraft, spacecraft, bicycles, medical devices, jewelry, high-stress components such as connecting rods on high-end sports cars, and some premium sports equipment and consumer electronics.
LEADRP offers a complete Titanium CNC machining service and can produce custom Titanium parts in various shapes and grades, including Titanium Grade 1, Titanium Grade 2, and Titanium Grade 5.
There are many more other metal and alloy materials for different applications. No matter it’s on our material list or not, we could source them for your project.
CNC Plastics Material
ABS is a plastic material with three main ingredients: acrylonitrile, butadiene, and styrene. Each of these monomers imparts specific properties, making ABS terpolymer with robust features. ABS has good strength, toughness, and resistance to impact and temperature. It is easily molded and gives a high-quality glossy surface finish. This plastic polymer does not have a specific melting point.
LEADRP offers a complete ABS machining service and can produce custom ABS parts in various shapes and grades.
Nylon plastic (PA) is a synthetic thermoplastic polymer commonly used in injection molding applications. It’s a versatile, durable, flexible material often used as a more affordable alternative to silk, rubber, and latex.
LEADRP offers a complete Nylon machining service and can produce custom Nylon parts in a variety of shapes and grades.
Polycarbonate(PC) is a thermoplastic polymer containing carbonate groups in their chemical structures. Polycarbonate has good stiffness and thermal resistance due to its molecular structure and reasonably high viscosity. Polycarbonates can be molded and thermoformed with great ease, making them a popular choice for a wide range of products.
LEADRP offers a complete polycarbonate machining service and can produce custom polycarbonate parts in a variety of shapes and grades.
Polyethylene (PE) is generally divided into multiple groups based on density. These include low-density polyethylene (or LDPE), medium density polyethylene (MDPE), high-density polyethylene (HDPE), and ultra-high molecular weight polyethylene (UHMWPE or UHMW). The higher the density, the higher the tensile and flexural strength, chemical and abrasion resistance, and surface hardness.
LEADRP offers a complete Polyethylene machining service and can produce custom Polyethylene parts in a variety of shapes and grades.
PET(Polyethylene Terephthalate) or polyester is a semi-crystalline resin with a good balance of strength, stiffness, toughness, a natural high gloss finish, excellent chemical resistance, and good dielectric properties. PET is approved as safe for contact with foods and beverages worldwide; PET is sustainable, completely recyclable, and they are the most recycled plastic. PET is commonly used in Plastic components in electrical products, Electrical encapsulation or insulation, Electrical insulation polymers, Connectors for electrical, Packaging or containers for consumables and food, and Appliances.
LEADRP offers a complete PET injection molding service and can produce custom PET parts in various shapes and grades.
Acrylic(PMMA) is a glass-like plastic, their excellent weatherability, good resistance to fading caused by UV and fluorescent lighting, and high resistance to scratching, durability, and natural transparency mak it a good material choice for food storage containers, refrigerator drawers,automotive and consumer products. Acrylics are also well-suited to overmolding and other specialized injection molding processes.
LEADRP offers a complete Acrylic injection molding service and can produce custom Acrylic parts in various shapes and grades.
Polyoxymethylene (POM), also known as Delrin® or Acetal, is a thermoplastic engineered material used to make parts that require increased stiffness, low friction versatility, and more excellent dimensional stability. POM has high tensile strength, wear resistance, creep and warp resistance, and overall toughness and durability. POM is widely used in manufacturing gears, bearings, conveyor parts, automotive parts, sporting equipment, electrical components, sliding and guiding parts, and so on.
LEADRP offer a complete POM/Delrin®/Acetal injection molding service and can produce custom POM parts in various shapes and grades. LEADRP will work with you to produce injection molded Delrin® parts that meet the exact specifications of your project.
Polypropylene (PP) is a polyolefin or saturated polymer, like polyethylene (PE) and polybutene (PB). PP is one of the most versatile polymers with good chemical resistance, fatigue resistance, better temperature resistance, and lower density than HDPE.
PP is widely made for buckets, bowls, crates, toys, medical components, washing machine drums, battery cases, and bottle caps. PP can be elastomer modified for bumpers and talc-filled for added stiffness at high temperatures.
LEADRP has been producing injection-molded polypropylene parts for over 10 years. Our team has extensive experience and expertise in delivering molded PP parts in even the most complex shapes. We can help you decide which of these plastic materials is best suited to your specific application.
Polytetrafluoroethylene (PTFE), also known as Teflon®, is a synthetic tetrafluoroethylene with numerous applications. PTFE has high thermal stability, good chemical resistance, and high-temperature resistance.
PTFE products also have excellent sliding properties, electrical resistance, and a nonstick surface. PTFE can be reinforced with glass fiber, carbon, or bronze additives to improve mechanical properties. Due to its structure, PTFE is frequently formed into semi-finished products using compression molding and then machined with cutting/machining tools.
PEEK is a family of high-performance thermoplastics. The name PEEK is derived from the words polyether ether ketone.
PEEK is a engineering plastic used for a wide range of applications where it needs to be strong and tough. It has good chemical resistance and can withstand high temperatures up to 260°C.
PEEK has excellent mechanical properties, making it suitable for applications such as medical implants, automotive components, and even aeronautical parts. PEEK is also used in electronic components such as connectors and insulators.
For Example: High Performance Plastics, Engineering Plastics, Industrial Plastics, Biocompatible Materials, Food Safe Plastics, and Other Modified Thermoplastics.
Resources of CNC Machining
If you’re interested in learning more about CNC machine in the crucial trade that it is. One of the best places to do that is through the Titans of CNC academy. This online resource will teach you from the ground up how to design parts in machine them for Free, whether you have acnc machine or not, you can also get Free trials of Autodesk and cam software to play around with. Or if you’re a student, you can get the programs completely Free.
FAQ
Q: What language is used by CNC machines?
A: CNC machines are primarily programmed using G-code though M-code is also acceptable.
Q: Are CNC and VMC the same?
A: No. A computer controls CNC machines. A VMC is a kind of CNC machine used to cut metal.
Q: What is the difference between PLC and CNC?
A: Programmable Logic Controller (PLC) is sequential while CNC is conditional.
Q: Who invented CNC machining?
A: John T. Parsons
Q: What is the significance of CNC machining?
A: As the process is automated, it increases efficiency, lowers costs and increases accuracy.
Q: What materials can be used in CNC machining?
A: Depending on the application, common materials include stainless steel, copper, brass, aluminum, titanium, foam, polypropylene, ABS, POM, PC, Nylon and more.
Q: What are the five different CNC machines?
A: CNC lathe machine, router machine, milling machine, laser cutting machine and plasma cutting machine.
Q: What is the difference between DNC and CNC?
A: A direct numerical control (DNC) system uses a mainframe computer to operate multiple machines. DNC refers to the networking of more than one CNC machine.
Q: What is an NC machine?
A: Numerical Control (NC) machines receive instructions from a punch card, whereas a CNC machine receives instructions from a computer.
Q: What industries use CNC machining?
A: Aerospace, medical device, photonics, defense, electronics, transportation and more.
Q: What type of finish is produced by CNC machining?
A: Some CNC machines, such as the CNC mill, may leave visible tool marks. Because of this, additional finishing may be required to finish the part.
Q: What are the standard finishes for CNC parts?
A: Bead blast, anodized, chem film, passivation, powder coat, electropolishing, electroless nickel plating, silver plating and gold plating.
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