CNC (Computer Numerical Control) and forging are two distinct manufacturing processes with different characteristics and applications. Here are the key differences between the two:
CNC:
Process: CNC machining is a subtractive manufacturing process. It involves the removal of material from a solid block or workpiece using computer-controlled cutting tools. The cutting tools follow pre-programmed instructions to shape the workpiece into the desired form.
Material: CNC machining can be used with a wide range of materials, including metals, plastics, wood, and composites. The material is typically in a solid or semi-solid form, such as a billet, block, or sheet.
Flexibility: CNC machining offers high flexibility in terms of design and customization. Complex geometries, intricate details, and precise tolerances can be achieved with CNC machining. It is particularly suitable for low to medium production quantities and rapid prototyping.
Surface finish: CNC machining can produce excellent surface finishes with smooth and precise features. However, the quality of the surface finish may depend on factors such as the material being machined, cutting tools, and machining parameters.
Forging:
The process of forging is a formative manufacturing technique that entails the shaping of metal through the application of compressive forces. This involves heating the metal and subjecting it to pressure, typically using tools such as hammers, presses, or dies, in order to deform and mold it into the desired shape. The forging process finds extensive application in a variety of components, such as connecting rods, crankshafts, gears, flanges, valve bodies, bolts and fasteners, shafts, rollers and gears. The typical steps involved in this process are outlined below:
1, Heating: The process commences by heating the metal, typically steel or alloy, to a temperature above its recrystallization point but below its melting point. This thermal treatment renders the metal more ductile and amenable to shaping.
2, Forming: Once heated to the appropriate temperature, the metal is positioned on a die – a tool with a specific shape or impression into which the heated metal will be forged. There are two primary types of forging processes called open die forging and closed die forging.
In open-die forging, the metal is partially exposed to the die during shaping. The heated metal is positioned on a level anvil and shaped through repetitive hammering or pressing between the dies. This technique is employed for larger components requiring straightforward shaping or when only a limited number of parts are necessary.
In closed-die forging, the process known as impression-die forging, is employed for the production of intricate and precise shapes. In this method, the heated metal is completely enclosed within dies that possess the desired shape and form. Subsequently, the metal undergoes compression between these dies to acquire the exact configuration of their cavities.
3, Cooling: following the forging process, the metal is gradually cooled to preserve its enhanced mechanical properties through a controlled cooling technique known as “annealing,” which serves to enhance strength and alleviate internal stresses.
Forging offers several advantages over other metalworking processes, such as:
1,Enhanced strength and improved mechanical properties: Forged components have greater strength and toughness compared to cast or machined parts, making them suitable for critical applications.
2, Better grain structure: The forging process aligns the grain structure of the metal, resulting in superior performance and resistance to fatigue and impact.
Reduction in material waste: Forging minimizes material wastage compared to other manufacturing methods like machining.
3, Cost-effectiveness: Forging can be a cost-effective manufacturing method for high-volume production runs of components with repetitive shapes. It can efficiently produce parts that require high strength and have simple or moderate complexity.
But forging parts also come with certain disadvantages that need to be addressed. One of these is the characteristic surface texture and grain flow resulting from the deformation process during forging. This can affect the overall appearance and functionality of the part.
To overcome this issue, additional machining or surface finishing operations may be necessary to achieve the desired surface characteristics. These processes can include grinding, polishing, sandblasting, or coating. The choice of method will depend on factors such as material type, part geometry, and intended use.
In summary, CNC machining is a subtractive process that offers high design flexibility and precise machining capabilities for a variety of plastics or materials. Conversely, forging is a formative process that enhances the strength and durability of metals, making it suitable for producing high-strength components. The choice between CNC machining and forging depends on factors such as desired part characteristics, material properties, production volume, and cost considerations. The noteworthy point is that in certain instances, engineers may opt to utilize the forged component and subsequently employ CNC finishing techniques to achieve precise dimensions and a flawless surface.