Introduction

CNC means Computerized Numerical Control. It is a computerized manufacturing process in which pre-programmed software and code govern the movement of production equipment. CNC machining is used to manage a wide range of complicated machinery, such as grinders, lathes, and mills, all of which are used to cut, shape, and build various components and prototypes.

· History of CNC machining

The first CNC machine was built by James Parsons in 1949. Parsons worked on an Air Force Research Project and was a computer pioneer. The research focused on ways to improve helicopter blades and aircraft skin.

Parsons was able to estimate helicopter airfoil coordinates using an IBM 602A multiplier. He then fed the data into a punched card using a Swiss jig borer. As a result of this study, several helicopter blades and airplane skins have been produced. According to accepted CNC history, this is the first CNC machine. Parson was awarded the Joseph Maria Jacquard Memorial Awards for his achievements.

· The Beginnings of CNC Work

In the 1940s and 1950s, early CNC machines employed punched tape, which was then widely used in telecommunications and data storage. Analog computing technologies supplanted this technology. Digital technology arose in the 1960s and 1970s, automating and improving the manufacturing process.

Parsons received recognition for his early work. The Numerical Control Society presented him with the first Joseph Marie Jacquard Memorial Award in 1968. In 1975, the Society of Manufacturing Engineers designated Parsons “The Father of the Second Industrial Revolution,” and presented him with an honorary plaque.

· CNC Machining evolution

CNC machines have evolved from simple punch-tape-controlled machines to nearly completely automated machines with the capability of working up to five axes. Anyone who works with CNC machining knows how far the technology has come in such a short period. Examining any historical period allows us to appreciate the present while continuing to innovate for the future. Companies are constantly working to make CNC machining faster, more efficient, and more accurate.

NC machines were originally controlled by punch cards with a series of codes. G-codes were the name for these codes. The codes were created to direct the machine on how to position itself. The fact that these machines were hardwired made it difficult to adjust the pre-set parameters a major issue. G-codes were still employed as a control method after CNC machines took over. They were now developed, controlled, and conducted using computer technology. Today, G-codes in CNC machines have been merged with logical commands to establish a new programming language. This language is known as parametric programmes, and computers that use it allow workers to make changes in real time.

What is precision CNC machining?

Precision CNC machining is a method for producing dimensionally precise components. This is commonly used in the aerospace, automobile, and modern electronics sectors, among others, to manufacture complicated components. The optimal material selection is critical for achieving precision in CNC machining, together with modern technologies and competent workmanship. Dimensional stability, machinability, and workability, as well as corrosion resistance and impact resistance, are key requirements for precision CNC machining materials.

Importance of CNC machining in manufacturing

CNC machining has become indispensable in the production industry as a result of the extensive usage of computers. Old industrial equipment like lathes, routers, drills, and millers are now operated by unique computer programmes to achieve precision levels of control, making CNC machining stand out.

CNC machining has been popular in many industries in recent years because it has streamlined the manufacturing process.

Some benefits CNC machining are:

· Better efficiency

Better efficiency is one of the reasons CNC machining is innovative. CNC machines can function without stopping till maintenance is required. When there is still a lot of work involved in the production process, a few shifts are unavoidable because humans cannot function like machines.

· Higher precision level

CNC machines follow preprogrammed instructions that provide the same commands and paths to follow. When every finished component is anticipated to be desirable and good, waste can be cut greatly, and lower costs lead to more appealing selling prices.

· Better production safeguards

If workers wander off during the manufacturing process, it might be risky. Let’s say the raw materials are sheared, welded, punched, or laser cut. Each motion of CNC machines can be perfectly accurate and adaptable with preprogrammed orders, reducing occupational injuries to a greater extent.

Precision CNC machining equipment types;

When it comes to machining, a number of procedures must occur in set sequence to produce the greatest outcomes possible. Here we explore a handful of these operations — turning, drilling, and milling. Machining is a very versatile industrial method. The three procedures stated above can be used to machine a variety of materials.

· CNC Milling

Milling is a machining method that removes material from a workpiece by rotating multi-point cutting tools. In CNC milling, the workpiece is fed to the cutting tool in the same direction as the cutting tool’s rotation, whereas in manual milling, the workpiece is fed in the opposite direction of the cutting tool’s rotation. Face milling—cutting shallow, flat surfaces and flat-bottomed cavities into the workpiece—and peripheral milling—cutting deep cavities, such as slots and threads—are two operational capabilities of the milling process.

·  CNC turning

Turning is a machining operation that removes material from a spinning workpiece using single-point cutting tools. To produce cylindrical parts with external and internal features such as slots, tapers, and threads, the machine, Typically, a CNC lathe machine—feeds the cutting tool in a linear motion around the spinning workpiece’s surface, eliminating material around the circumference until the required diameter is reached. Boring, facing, grooving, and thread cutting are all capabilities of the turning process. When choosing between a CNC mill and a lathe, milling, with its revolving cutting tools, is preferable for more complex items. Lathes, on the other hand, function best for creating circular parts since they have spinning workpieces and stationary cutting tools.

· CNC drilling

Drilling is a machining operation that produces cylindrical holes in a workpiece using multi-point drill bits. In CNC drilling, the spinning drill bit is fed perpendicular to the plane of the workpiece’s surface, resulting in vertically aligned holes with sizes equal to the diameter of the drill bit used in the drilling operation. Angle drilling operations, on the other hand, can be carried out with the use of specific machine configurations and workholding equipment. Counterboring, countersinking, reaming, and tapping are all operational skills of the drilling process.

Commonly used metal materials in precision CNC machining

• Stainless steel
• Brass
• Titanium & titanium alloys
• Steel
• Aluminum & aluminum alloys
• Copper
• Carbon steel

· Stainless steel

The most widely utilized material for precision CNC machining is stainless steel (SS). The phrase stainless steel refers to a variety of grades, including SS303, SS304, and SS316. The number of doping elements added is the difference between all of the materials in the SS range. Sulfur is added to SS303 for improved machinability and rust resistance. Nickel and chromium are added to SS304 to increase toughness and decrease magnetic characteristics. SS316, on the other hand, is a marine-grade stainless steel that contains molybdenum. Weldability, machinability, and corrosion resistance are all advantages of SS316. All of the stainless steel grades described above are suitable for precise CNC machining.

· Brass

Brass is a copper and zinc alloy. It’s a highly soft metal that can be machined without lubrication in many cases. It’s also a material that works well at room temperature, so it’s frequently used in applications that don’t require a lot of strength. Brass is classified into several types based on the zinc content. Corrosion resistance reduces as this proportion rises.

Brass is polished to a high sheen that resembles gold. It’s for this reason why it’s frequently used in cosmetics. Brass is electrically conductive but not magnetic, thus it can be recycled easily.

Brass can be welded, but low-temperature procedures like brazing or soldering are more common. Brass is also useful for tools in potentially explosive conditions since it does not spark when struck with another metal. Brass has natural antibacterial and antimicrobial characteristics, and its application in this area is still being researched.

Plumbing fittings, home ornamental hardware, zippers, naval hardware, and musical instruments are all made of brass.

· Titanium & titanium alloys

Titanium and titanium alloy materials have a steel-like, shiny look and a density of 4.51g/cm3, which is only 57 percent that of steel. It has a number of advantages, including low density, light weight, high specific strength, outstanding performance at both low and high temperatures, and great corrosion resistance.

Titanium and titanium alloys are commonly employed in rockets, missiles, satellites, spaceships, warships, the military, medical treatment, and the petrochemical industry; they are also non-magnetic. They are ideal materials for making deep-sea submarine shells since they are non-magnetic and have high strength.

TC4 (Ti-6Al-4V, GradeF5, Grade5), TA7 (Ti-5Al-2.5Sn), and commercially pure titanium TA1, TA2, TA3 are the most commonly used titanium and titanium alloys.

· Steel

One of the metal alloys utilised in precise CNC machining is steel. It has good dimensional stability and is easy to machine. For precision CNC machining, different grades of steel are considered. Mild steel, carbon steel, plain carbon steel, and low and high alloy steel are among them. Mild steel has a lot of ductility, but carbon steel has a lot of strength. For low ductility and high strength applications, plain carbon steel is preferred. By doping alloy steel with molybdenum or nickel-chromium, it can be manufactured to meet specific specifications. As a result, alloy steel can be utilised in applications that need corrosion resistance, durability, weldability, and other characteristics.

· Aluminum & aluminum alloys

Aluminum is a very light metal. It is non-magnetic by nature, making it ideal for CNC machining. It has a low deformation factor, great dimensional stability, and is resistant to impact. As a result, despite various conditions such as temperature variations, external impact, and so on, aluminium and aluminium alloys maintain exact dimensions. Aluminum, like stainless steel, has gained popularity in many grades.

 A few prominent ones are listed below.

1. Aluminum 606 :- It is the most common aluminium grade. It has great strength, corrosion resistance, toughness, and weldability, among other mechanical qualities.
2. Aluminum 7075 :- It has a high fatigue resistance and is utilised in a variety of industrial applications. This material is used to make aircraft wings and fuse glasses.
3. Aluminum 2024 :- It is employed in military and aerospace applications because of its strong temperature resistance, shock resistance, and fatigue endurance.
4. Aluminum 5052 :- It is a chemical and corrosion resistant metal. Because it cannot be heated, it is employed in marine applications.
5. Aluminum 6063 :- It is a heat-treatable alloy with excellent weldability and tensile strength. It can be used to create intricate components.

· Copper

Copper is corrosion resistant since it is a non-ferrous metal. It has good electrical conductivity and durability, making it ideal for precision-made electronic components. Brass, bronzes, nickel silver, copper-nickel-alloy, and other copper alloys are utilized in a variety of applications. Because the list of raw materials for precision CNC manufacturing is extensive, it is critical to recognize that material selection must be completed quickly.

· Carbon steel

This material appeals to machinists because it is simple to work with and can be polished in a variety of ways. Because it is robust and operates well in severe situations, carbon steel is perfect for CNC machining services.

This steel has a lower melting point due to the greater carbon content. It’s also more malleable and bend-resistant. Oil, gas, and petrochemical industries can use the material.

Commonly used plastic materials in precision CNC machining

Plastic is an excellent material for CNC machine shops. The material is made up of bendable synthetic or semi-synthetic organic molecules. It aids in the formation of solid parts.

The low cost, ease of manufacture, and versatility of plastic are all advantages. Plastic is a great alternative to traditional raw materials like steel, metal, and ceramic.

Plastics are used in almost every industry, including the medical field. Plastics can be utilized to produce containers for the medical industry.

· ABS

ABS, or Acrylonitrile Butadiene Styrene, is a common CNC plastic that satisfies the demands of a wide range of sectors because to its material qualities and low cost. ABS is one of the most machinable plastics available at a reasonable cost of raw material. Both of these characteristics have led to the material’s adoption in a variety of prototype and end-use applications.

ABS offers strong impact resistance and exceptional temperature and chemical resistance. ABS’s exceptional machinability results in products with excellent surface finishes. Surface metallization, electroplating, bonding, and other post-processing treatments are available for machined ABS components.

· Nylon

Nylon is a widely used synthetic polymer with a variety of qualities, including mechanical strength, shock absorption, and wear resistance. Despite the inexpensive cost of raw nylon material, the medium machinability rate of the material might impact the cost of some applications, particularly those requiring tight tolerances and fine details.

It’s commonly used to make all types of structural elements and as a less expensive alternative to metal components. Plastic machining producers from a variety of sectors value the material’s electrical insulation and chemical resistance.

· PMMA Acrylic

Acrylic, or PMMA, is a clear CNC plastic material with high strength and stiffness. Many manufacturers like the plastic because of its superior machinability and inexpensive raw material cost.

PMMA may be found practically everywhere because it is one of the most widely used plastics. Machinists frequently utilize it as a glass substitute in the building, interior design, and chemical industries because of its transparency. Billboards and other types of signs are made from this weather-resistant material by machinists.

· PEEK

PEEK is a thermoplastic with a unique mix of mechanical characteristics. Chemicals, wear, creep, fatigue, liquids, and temperatures of up to 260°C (480°F) are all resistant to this material. It’s also light, durable, and insoluble in all solvents. PEEK is also biodegradable and recyclable.

In CNC machining, PEEK, like nylon, is frequently used to substitute metal. Piston units, crucial aviation engine parts, and dentistry syringes are just a few examples of common uses.

PEEK is not UV resistant and does not hold up well when exposed to halogens or salt, despite its many advantages. It’s also one of the more costly CNC machining plastics on the market, therefore product teams should only use it for the most difficult jobs.

 

When selecting a material for a CNC machining project, these are the factors to keep in mind.

· The Machined Component’s Purpose:

The purpose of the component being machined must be the primary consideration in material selection. CNC machines are used to make a variety of items in industries such as mechanical, aerospace, automotive, and electrical. The use of a machined component will assist you in making the best option. It’s also crucial to consider whether the component will have multiple applications. The aerospace sector, for example, requires lightweight yet strong materials for production. As a result, entire metals may not be suitable for aircraft applications, but composite materials may.

· Dimensional Tolerance and Stability

Aeronautics and aerospace industries demand components with extremely accurate dimensions and high stability. Materials having strong dimensional stability, or a low deformation factor, will be required in such circumstances. Different materials react differently to the forces created by the cutting tool. As a result, the item used must be able to match the strict tolerances required. The easier it is to obtain tighter tolerances, the more machinable a material is.

· Cost of the Material

Sometimes the best material for a part is also the most expensive. The cost of obtaining such material far exceeds the production budget. It becomes vital to investigate other low-cost materials. However, functionality, strength, hardness, chemical tolerance, electrical characteristics, and other attributes must be carefully considered to decide whether such a material is a viable low-cost alternative to the best appropriate material. Steel 1.4571, for example, has good wear and corrosion resistance as well as machinability.

It is, however, twice as expensive as steel 1.7131, which has similar wear resistance. Steel 1.7131 is a fantastic alternative to steel 1.4571 for applications where wear resistance is a top priority.

· Availability of material

When it comes to choosing materials for CNC machining, availability is crucial. Sometimes the best material isn’t accessible in large enough numbers to keep production going. On the other side, obtaining such materials may be challenging. It’s a good idea to choose materials that meet the functional requirements and are widely available, especially if the part will be mass-produced. Materials that are easily accessible ensure that CNC machining is completed in the quickest and most effective manner feasible.

· Appearance of the material

When choosing a material, aesthetics is frequently the last thing on people’s minds. However, in some instances, it is critical. The outward look of various products will impact whether or not they are accepted by consumers. Specific physical characteristics, such as colour or a smooth surface finish, may be required for consumer products.

After machining, metals often have a superior surface finish, requiring less work during polishing. Plastics are frequently accessible in a variety of colours, whereas metals require coloration after processing.

Conclusion

CNC machining is a highly versatile manufacturing technology that requires a thorough evaluation of project requirements in order to select the best material for the job.  Machine shops can supply a variety of machined products with exceptional quality and accuracy using the right raw materials. As a result, choosing raw materials is essential for a CNC machine shop to manufacture the parts that industries want.

The most significant component of precise CNC machining is selecting the right material and establishing a balance between cost, quality, and time since it is required to get the desired result.