CNC Machining

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What is CNC Machining

The word 'CNC' in CNC Machining stands for Computer Numerical Control. CNC Machines manufacture millions of components per day in multiple industries around the world. Commonly used materials are Metals, Wood, and Composites.

So, what is CNC Machining? All automated motion control machines primarily have three components – a command function to instruct motion what needs to be done, a drive/motion system to execute the received commands, and feedback system to tell the command centre that the actions have been executed. CNC machining is the process of using a cutting tool (drive/motion system) to remove material from the material block by taking command from the computer.

The language which the Computer uses to convey information or instrutions to the drive/motor system are usually GCodes or MCodes. GCodes and MCodes are different modes of encoding that tells the cutting tools what to do (milling, drilling, boring etc.), where to do (co-ordinates), and how much to do (depth, length, etc.).

For example, G02 instructs the tool to create a clock-wise arc. GCodes are used with start and end co-ordinates to instruct the tool on where the operation should start and where it should stop.

CNC machining simplifies the manufacturing of complex parts and components that would usually be extremely difficult or expensive using other manufacturing processes.

Types of CNC Machines

Below are basic types of CNC machines:

Lathes: Simplest and oldest of all, this type of CNC turns the workpiece and moves the cutting tool to the workpiece. A basic lathe is 2-axis, but many more axes can be added using specific fixtures and add-ons to increase the complexity of cut possible. The material is held on chuck, rotates on a spindle and is pressed against a grinding or carving tool that makes the desired shape. Lathes are mostly used to make simpler objects that have cuts on only one-axis, that is along it's length.

Routers: CNC routers are usually used to cut large dimensions in wood, metal, sheets, and plastics. Standard routers operate on 3-axis coordinate with X and Y axis mounted on the head and depth along Z axis, so they can cut in three dimensions. However, 4,5 and 6-axis machines are also available for prototype runs and complex shapes.

Milling: CNC Milling Machine uses a rotating cylindrical cutter (tool) to move along multiple axes, to create slots, holes and details in material as instructed by the Computer. Commonly, three to five axes are used for creating much more precision and detail.

Plasma Cutters: The CNC plasma cutter uses a powerful laser to cut the material in desired shapes.

CNC Machines are capable of manufacturing wide-array of complex parts with incredible precision.



Machining Processes

Multiple operations are used in manufacturing a single component by CNC Machining. There are major 5 types of processes, Milling, Turning, Drilling, Grinding and Routing.

Milling

It is an operation where the cutting tool rotates on a spindle which could be vertically or horizontally mounted. When the cutting tool comes into contact with the workpiece, it removes material from it in form of chips.

Milling operations include, but are not limited to:

  • End milling
  • Chamfer milling
  • Face milling
  • Drilling,
  • Boring,
  • Tapping, etc.

Milling is a very universal fabrication method with great accuracy and incredible tolerances. Milling is quick and is suitable for a wide-array of materials.

The major disadvantages is large amount of waste generated in form of chips. Also, the need for a variety of tooling and high cost of equipment are a disadvantage.

Turning

In Turning, the workpiece rotates instead of the tool. The workpiece is usually mounted on chuck and rotates with multiple speeds. The cutting tool moves in different axes and makes cut on the rotating workpiece.

CNC turning is commonly used for producing cylindrical components, for example, shafts. Achieving high accuracy for a suitable types of limits and fits system is possible using CNC turning.

Drilling

While milling equipment can also produce holes on the surfaces, drills are meant for only one job, that is to drill holes.

Grinding

CNC grinding machines use a rotating grinding wheel, usually made of abrasive material, to remove the material from the workpiece. The objective is to give a high precision finish to the workpiece.

The achievable surface quality is very high compared to other processes. Therefore, it is used as a finishing operation on the components already manufactured using other manufacturing processes rather than creating directly the final piece from raw materials.

Routing

CNC routers work similar to CNC milling machines. Here also the rotating piece is the cutting head while the workpiece is stationary. Routers are a perfect fit for cutting softer materials like Wood, or MDF boards, and not metals, that do not require very high accuracy. Routers consume comparatively lesser power and are quicker.

Materials

1. ALUMINUM

Aluminum alloys, being softer in nature than it's counterparts, Steel and Iron, are easy to machine in large volumes, have a good strength-to-weight ratio, and high thermal and electrical conductivity. They are also naturally resistant to corrosion. Aluminum 6061 is an all-purpose aluminum alloy widely used for CNC machining. It is found typically in automotive components, bike components, sporting goods and components, and other recreational items. This material is highly and easily machinable; however, it can be expensive than other metals and doesn’t hold up well in the presence of saltwater or certain chemicals. Aluminum 7000 series, especially 7075 is a step up from 6061. Ideal for aerospace frames and high-performance and light-weight recreational equipment, it’s the strongest commercially available aluminum alloy that one can find today.

2. STAINLESS STEEL

Stainless steel alloys are strong and resistant to corrosion, wear and distortion. 300 series stainless steel includes sulfur for improved machinability, but this material has a number of limitations.

303 stainless steel is best suited for nuts, bolts, non-marine grade fittings, shafts, and gears but it has some serious limitations such as it can not be cold-formed, heat-treated, or welded. Special care must be taken with speed, feeds and sharpness of the cutting tools during CNC machining.

304 is a non-magnetic, all-purpose stainless steel for CNC machining known for its toughness. It is readily machinable and corrosion-resistant just like 303. But unlike 303, 304 can be welded. 304 is best suited for a wide-array of industrial and consumer applications, kitchen accessories, tanks and pipes, architecture, and more.

316 stainless steel, due to the addition of Molybdenum, is even more corrosion-resistant than 304 or 303. 316 is strong, weldable, and one of the few marine grade stainless steels.

It’s impossible to tell stainless steels apart by sight alone, since engineers should make sure to test the raw material to confirm the characteristics of the steel they’re using before putting it to use.

A detailed version of specifications and use cases of Stainless steel can be found on our resources page. Link: <Insert Link>

3. CARBON STEEL

Carbon steel grade 1045 is a mild grade of carbon steel. It is less expensive than most stainless stell yet stronger and tougher, hence manufacturers often machine with this material instead of stainless steel. 1045 is easy to machine, weldable, and can be hardened or heat-treated to achieve various level of desired hardnesses.

Carbon Steel 1045 is ideal for nuts, bolts, gears, shafts, connecting rods, and other strong, small mechanical parts. It can also be used for architectural applications, but since it is prone to rust and corrosion, it must first be surface-treated to prevent rust and corrosion.

4. TITANIUM

Titanium is known for its high strength, toughness, and corrosion resistance. It is often employed to manufacture parts for the most demanding aerospace, military, and industrial applications where there is very little to no margin for error. This material is also biocompatible and hence is suitable for use in medical device manufacturing along with surgical implants.

However, titanium is more expensive than any other metal available in its commercial form. Because of it's toughness, it doesn’t polish well; and it is a poor conductor of electricity. Engineers should also be aware that titanium is challenging to machine, and requires special tooling.

5. NYLON

Nylon is an all-purpose thermoplastic. It has low-friction and is often used as an alternative to metal in CNC-manufactured parts. This material is stiff, strong, impact-resistant, chemical-resistant, but is also surprisingly elastic. Nylon responds well to additives and fillers, so it can be manipulated as per the need to achieve the desired properties.

Some popular applications for nylon include electrical molding, fuel system components, gears, food packaging, fabric, etc. However, nylon is hygroscopic, meaning it absorbs readily absorbs moisture from air, which may negatively impact the dimensional stability of a part.

Material Selection

Material selection is an incredibly important part of any manufacturing process, but engineers and product teams must be especially diligent when it comes to selecting materials for CNC machining. Since this process is compatible with a wide variety of materials — from metal to fiberglass to wood — it’s easy to mistakenly choose a material that’s sufficient for the project but not the best-suited. In this article, we’ll touch on key considerations for CNC machining material selection and give an overview of some common options.

Key considerations for choosing CNC machining materials

Before getting into the particulars of material selection, product teams must first take stock of their project requirements. Start by considering these four questions:

1. How will the part be used?

Engineers must consider their part’s end-use and where it will be used, as these factors will have a significant impact on material selection. For example, stainless steel and carbon steel are both suitable for CNC machining, but only stainless steel is naturally corrosion-resistant. Choosing the wrong kind of steel here would compromise a part’s longevity. FDA, FAA, as well as any industry-specific regulations should also be top of mind.

2. Does weight matter?

If a part must be light — a common requirement when manufacturing for automotive and aerospace applications — there are plenty of low-density metal options available. Manufacturers might also consider using a plastic like ABS to keep weight down if they’re willing to sacrifice strength.

3. Does the part require high strength or heat resistance?

Strength can be measured in many different ways (tensile strength, wear-resistance, etc.), so engineers should determine what kind of strength — and to what degree it matters — is required for their part. These parameters will impact the size of the pool of viable materials. Similarly, temperature requirements will exclude certain materials from the outset. Engineers should also think about whether their part will be exposed to fluctuating temperatures, as nearly all materials expand or contract in response to temperature changes.

4. What is the project budget?

Material costs almost always influence material selection. The goal of most product teams is to select a material that maximizes desired material properties and performance while minimizing expenditure. Material costs are especially important when it comes to CNC machining because this process produces a relatively large amount of scrap material behind. Some materials — such as specialty metals — are extremely expensive, which could have a major impact on the cost-efficiency of the entire project, considering scrap material output. Engineers should carefully evaluate their budget before making any final decisions.

Commonly used CNC machining materials

Since any material — metal or plastic — that’s hard enough for machining can be used for CNC manufacturing, product teams are spoiled for choice. This short list provides a quick gloss of some of the most common materials used in CNC manufacturing today.



Applications of CNC Machining

CNC machining is a widely used manufacturing processes with applications in multiple industries. It is used as a standalone manufacturing process as well as a value added manufacturing processes. For example, shafts are primarily manufactured by CNC machining while engine or pump casings are primarily made using Metal Casting process but then are finished using CNC machining process.

Below is the list of some of the components that use CNC Machining processes for manufacturing

1. Medical Industry
  • Cavities Molds,
  • Prosthetics
  • Hip stems or cups
  • DNA/RNA auto extruder parts
  • Medical Image Camera Parts
  • Syringe Needles used to insert optic lenses
  • Tracking sensors
  • Surgical Instruments
  • Imaging Instruments

2. Automotive Industry
  • Flywheels
  • Piston rods
  • Drive housings
  • Pumps
  • Cylinders and Blocks for Engines
  • Exhaust parts
  • Fluid system
  • Lightning components
  • Suspension components
  • Carburettor housings
  • Valve retainers

3. Energy Industry
  • Valves
  • Gears
  • Fuel Pumps
  • Wind turbine wear components
  • Bushes
  • Liners
  • Grippers
  • Valves
  • Seals
  • Solar Cell Wafer Holders

4. Agriculture

  • Transmission Housings
  • Gearbox Casings

5. Military

  • Locking devices enhancing aim of weapons
  • Firearm body protection
  • Sights
  • Cocking Handles

6. Semiconductor
  • Ultrasound-air-bearing wafer chip probing test parts
  • saw and sorter equipment parts
  • Assembled spin chucks (PIFE and SPM)

7. Automation

  • Power train auto assembly line,
  • Conveyor components
  • Clean Socket Lift Parts