super finishing machining

SUPER-FINISHING MACHINING: – 1) Introduction

Superfinishing processes are also known as Microfinishing – micromachining. The superfinishing process is used for increasing mirror and precise finishing to improve surface finishing.

After a metal part is a gripped to an initial finish. The abrasive is reciprocated or oscillated or rotated while the workpiece is reciprocated or rotated in the specified direction; these actions are what causes the cross-hatching. The geometry shapes of the abrasive depend on the geometry of the workpiece surface; a rectangular and concave-convex shapes are for cylindrical surfaces and cups, dovetails and wheels are used for flat and spherical surfaces. It is super finished with a specified grit solid abrasive.

Super-finishing can help to get a surface finish up to 0.01 μm.

A lubricant is used to minimize heat and increase the heat transfer rate, which can affect the different mechanical and metallurgical properties, and carry away the burr or chips; kerosene is a common lubricant.

Abrasive Particle: –

There are few common abrasives include aluminum oxide, silicon carbide, cubic boron nitride (CBN) and diamond used for superfinishing.

Aluminum oxide is used for “roughing” operations where Silicon carbide is used for “finishing” operations. CBN and diamond are not as commonly used because it’s kinda expensive compare to silicon carbide, but find use with specialized materials such as ceramics and carbide tools too. Graphite can be alloyed with other abrasives to add properties like lubricity and can help to enhance the quality of the product with an aesthetic finish.

Abrasive grains are mostly 5-8μm used with superfinishing.

Advantages and disadvantages

Advantages of superfinishing include:
increasing part life.
Decreasing wear.
Closer tolerances.
Higher load-bearing surfaces.
Better sealing capabilities
Elimination of a break-in period.
Aesthetic look.
Precise Dimensions.
Quality fits.
Sometimes reducing frictions.
Superfinishing certain parts make them more durable.

The main disadvantage is that superfinishing requires pre-operations like grinding or turning or shaping or milling or other operations as product required beforehand, which increases the overall cost. Superfinishing tends to lower the cutting rate and efficiency. Moreover, smaller chips and lower material removal rates lead to higher operation time. Superfinishing cutting tools are not harder and have to wear more quickly. However, they do not need to be truing or dressed.

There are a lot of applications in every manufacturing industry such as space industries, marine fields, robotics, automobile industries, nanotechnology, interior designer, oil and gas industries, electrical components, etc.

It has been proven that superfinishing certain parts makes them more durable. For example, if the teeth in a gear are superfinished they will last up to four times as long.

TYPES of the Super-Finishing process

  1. Honing
  2. lapping
  3. Super finishing

Requirement: In certain Circumstances very precise surface quality is required. Hence to remove some defects, to obtain desired surface finishing and to improve the quality of product finishing processes are used.

  1. Honing: – Honing is a superfinishing machining process that delivers a precision surface on a metal work-piece by scrubbing an abrasive grinding wheel against it in a controlled direction of the tool path. Honing is essentially used to improve the surface finish of the semi-finished product. However, it can likewise improve the surface completion of finishing.
  2. Lapping: – Lapping is a machining procedure wherein two surfaces are ground and grinding together with an abrasive particle between them, by mechanical movement or utilizing a machine.
  3. Superfinishing: – Superfinishing is a process wherein a rotating or reciprocating workpiece is done by a relatively soft stone with fine abrasive oscillating correspond to the workpiece surface.

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