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How Lapping Machines Work

7/16/2013 6:32:46 PM | by Anonymous

Lapping Machines

Lapping machines are tools used for fine finishing of metal surfaces. The lapping process or also called as grinding involves two surfaces rubbed together which can either be a hard metal cutting piece coated with an abrasive compound. Lapping machines apply rotational friction, speed and load in order to successfully grind metals. Different abrasives include emery, diamond, aluminium oxide and others. There are various types of lapping machines used for different applications. Vertical lapping machines are for finishing external surfaces while horizontal lapping machines work in both internal and external surfaces. Flat, valve and barrel type of lapping machines polish surfaces with the help of an operator. Lapping machines are preferred than hand lapping because the former is more accurate, faster and easier. The use of machines are also considered more cost efficient as the latter will require a huge number of manpower in order to meet the production demands. The monotonous nature of the hand lapping made the workers prone to commit mistakes and produce non-saleable products.

 

Pitch and ceramic are other materials used in the lapping process. They are meant to cut objects of harder quality. In terms of polishing materials, they can produce a very fine polishing such as a polishing cloth upon glass or flat surfaces to better than 30 nanometers when taken to the ultimate limit. The development of specialized polishing machines and the assistance of accurate interferometry made the latter possible.

 

Lapping machines are used to acquire not only specific surface roughness but also very accurate surfaces. These two are often taken similarly though they are actually referring to two dissimilar concepts. Without the aid of special equipment, 1 to 30 Ra is the typical range of surface roughness that can be achieved. Whereas 1 to 3 Helium Light Bands (HLB), the measurement used in determining surface accuracy or flatness, is the usual rate. One HLB is equivalent to around 0.000011 inches or 280nm. Besides flatness, the other configurations that can be done through lapping are convex and concave surface.

 

To determine if the lapping process is successful, the flatness of the surface has to be measured. The easiest way to do this is by using a height gage mounted on a surface plate. When setting this up, a part has to be positioned on three stands and adjusted according to minimum variation. This can be done by using a dial indicator to find TIR on differing side of the part measures parallelism. Another way of measuring flatness is through the use of co-ordinate measuring machine. Measurement can be easily taken with this machine compared to using height gage.

 

Reflection and interference of monochromatic light is another method commonly applied on lapped parts. In order to do this, optical light and monochromatic light source are needed. The optical flat is a piece of transparent glass produced as well by lapping and polishing on either one or both sides. The optical flat is placed on the lapped surface n the lapping machine where the monochromatic light will shone down through. The light that will pass through the glass will reflect off the workpiece resulting for the light to interfere with itself creating dark and light fringes.

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