Lapping Process: Definition, Working Principle, Types, Material, Advantages, Applications [Notes with PDF]

Lapping Process, one of the most demanding manufacturing process of any industry. Everything in this entire world is incomplete without finishing. In our daily life also, if we didn’t finish our day well then everything seems to be in trouble. Same is with the case of materials.

If you have applied each and every machining Process upon a material to make it better and usable but forgot to superfinish this, then its not that worthy.
So, here we are going to study about one of the most popular super finishing machining Process “lapping“.

So, stay tuned till end! You will get every bit of knowledge about Lapping Process.

What is Lapping Process?

Lapping is a low-pressure mechanical machining process used to increase dimensional accuracy and finishing of the workpiece. The lapping process uses fine Abrasive particles to perform the cutting action on the surface of the working surface.

The workpiece is rubbed on the lapping plate with the help of a machine or by hand, with Abrasive powder particles or Abrasive paste in the middle.

The lapping process smoothens the surface of the workpiece, this increases the performance and aesthetics of the workpiece. It is also used to ensure the correct balance between the two materials and to correct minor imperfections.

Working Principle of the Lapping Process:

The simple operation of the lapping process involves three things. A workpiece, a lapping plate and Abrasive particles.

Abrasive particles are poured over the lapping plate and the workpiece is drilled into it.

Abrasive particles remove very tiny microscopic material from the working piece when force is applied during a relative movement between the plate and the working surface.

Abrasive particles often reduce or flatten the tops and ridges found on the surface of the work.

Characteristics/ Signs of the Lapping process:

The following features of the Lapping Process are:

The size of the Abrasive grit used in the lapping process varies from 120 to 1200 mesh depending on the smoothness of the surface you prefer.

The abrasive used can be powdered or can be mixed with certain suitable oils or greases called motor.

The smallest amount of material is removed from a lapping process of approximately 0.025mm.

The lapping process can be done manually or with the help of machines.

Items that are usually lapped are as strong as steel.

The pressure applied during lapping is low compared to other surface finishing procedures.

Types of Lapping Processes:

There are two types of lapping procedures that are categorized by their domains:

• Hand Lapping Process
• Lapping Machine Process

• Hand Lapping Process

As the name suggests the lapping process in all hand-held forces is called “hand lapping”. There are two types of Hand Lapping Process involved in improving the quality of the workpiece.

1. Flat surface lapping:

The lapping plate here is made of gray metal. This consists of groves used to collect metal chips and waste Abrasive particles in them.

Abrasive grits of the desired size are sprinkled over the lap. The workpiece is then carefully rubbed against the lap.

Additional amounts of abrasive particles of the same mesh were added as needed. Use of appropriate fluids can be made if necessary. The procedure must be performed by a competent/skilled operator.

Once the lapping is complete, the lap should be cleaned for future use.

Note: Excessive use of abrasive particles can damage the lap. This can lead to improper termination of function and lap failure.

2. Cylindrical Lapping:

Laps used for the indoor and outdoor enclosure of cylinders are made of mild cast iron, brass, or copper.

For the lapping of the inner surface of the cylinder, the laps are made to be close to the internal diameter. Laps move randomly with axial motion w.r.t piece of work. This increases the upper end of the workpiece and the laps.

Abrasive particles are mixed with oil or grease in this process. The laps used to wrap the outside of the cylinder are called ring laps. It is provided with a repair screw with different diameters.

The workpiece to be lapped is held in place with a lathe to provide rotational motion. The ring lap is then reciprocated to the rotating workpiece. Abrasive particles mixed with certain oils and greases can be used.

• Machine Lapping Process:

When lapping operation is done using machines it is called a “machine lapping.”

Listed below are the different machine lapping processes used for different types of workpieces:

1. Vertical Lapping Machine:

Straight lapping settings consist of a lower lap, an upper lap, and a device to hold the function. The workpiece is kept in the lower lap and placed in a work position. The upper lap is used for loading and unloading the working piece.

Abrasive particles mixed with adhesive vehicles are inserted into the laps before operation. In the case of flattening, the lower lap is held upright, and in the case of cylindrical lapping the lower lap is allowed to move.

Various jobs are lapped using vertical lapping machines. For example, precision gauge blocks, roller coaster trucks, and ball bearing balls.

Another type of vertical lapping set includes Abrasive fabric wrapped around the lower lap. The same workpieces can be lapped by moving the work handle randomly. This is called “transposing.”

Note: The lower lap should be fixed during flattening as it may roll over.

2. Centerless lapping machine:

The centerless Lapping includes a control roller, lapping roller, workpiece, and a V notched fiber stick. The control roller is powered by the engine to provide rotating movement in the setting.

A lapping roller is used to lap a working piece from one side. The diameter of the moving roller is twice the width of the roller control. Both rollers are made of cast iron, due to their stability and low cost.

Rollers are attached to Abrasive particles. A V notched fiber stick is used to hold the working piece to be fed between the rollers. The workpiece is mounted on a roller at a very low rate with repeated movements.

The removal of material occurs due to the action of the Abrasive particles of the workpiece. An excellent finish of 0.05 microns can be achieved with the help of centreless lapping.

Removal of property is very slow in the case of centerless Lapping.

3. Spherical Lapping Machine:

The lapping machine used to lap Spherical objects has a different design. Two spindles are used in the case of spherical lapping.

The workpiece to be lapped is attached to the first spindle which provides circular motion to the working piece. Another spindle is used to hold the tool in place where a piece of work can be made.

Pressure is also applied to the workpiece with a tool spindle. As soon as the rotating movement is given a working piece the removal of the material occurs due to the connection between the Abrasive tool and the work.

4. Belt Lapping:

Belt Lapping uses a belt made of Abrasive cloth used for the lapping process. The belt is driven with the help of a motor. There are two wheels used to drive the belt.

The workpiece is hand-held with a belt over the wheel. Material removal occurs after the contact of the workpiece and the conveyor belt.

This is a good way to lap low-level jobs. There are no requirements for tying the workpiece.

Abrasive used for the lapping process:

Different types of Abrasives are used to lap the hardness of different materials.

The abrasives used to lap hard materials are usually silica carbide and alumina alloys.

Abrasives used to lap soft materials are chromium oxide, pure alumina, and garnet.

Lapping process Parameters/Specifications:

The following parameter says:

• Lapping speed: Lapping speed should be from 1.5 to 4 m/s.

• Lapping pressure: Lapping pressure depends on the hardness of the material and the Abrasive particles used. Lapping pressure varies from 10 to 30 kPa on soft materials and up to 70 kPa for hard materials.

• Lapping allowance: The Lapping allowance is directly proportional to the lapping time. As the lapping allowance increases, lapping time increases. The lapping allowance also depends on the material being lapped.

Some lapping allowance:

Cast iron- 0.2 mm
Aluminum alloy – 0.1mm
Soft steel – 0.05 to 0.1mm
Hardened steel – 0.005 to 0.02mm.

Advantages of the Lapping process:

Extend the surface finish of the workpiece by reducing the peaks and valleys to the visible area. It also gives a touch of beauty to the workpiece.

The Lapping process also extends the life of the mating parts by reducing friction between the mating parts.

Increases the geometry and size of the workpiece. It also ensures perfect balance between workpieces.

No thermal stresses are developed within the work environment due to the low temperatures involved in this process.

The process can be done with unskilled staff. This is due to the simplicity and lack of computer controls.

It enhances the similarity between the two parts kept together in each of the various integration functions.

Disadvantages of Lapping Process:

Lapping is an expensive process as the loss of Abrasives is more. This result is an increased use of Abrasive particles in the polishing process, which also results in higher production costs.

Another disadvantage of the lapping process is that the process is very slow. The rate of removal of the metal in the case of lapping process is very small. This makes processing time-consuming leading to a decline in productivity.

Waste management becomes a problem in the event of a lapping process. A large amount of waste in Abrasive is produced in the event of a extraction process. This makes it difficult to dispose of garbage.

Some Abrasive compounds may be embedded in the surface of the working piece resulting in subsequent damage to the working piece.

The process usually manually operated; these results increase hard work and increase production costs.

Applications of the Lapping Process:

Lapping Process is used to polish hard and brittle parts that are difficult to polish using other methods.

It is also used to make glass-like machines due to its slow removal rates.

The lapping procedure is widely used to perform metallurgical test models.

The lapping process is used to produce valves due to its precise removal feature.

That’s all from today’s article. Now its time to wrap up this. Hope you all like this information. Keep in touch with us for more mechanical engineering stuffs.

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