What Is Lapping Machinery?
Lapping Machinery is a general term for machine tools used to further finish a plane surface finished by a grinder, etc., to be parallel, smooth, and to the desired size.
In a lapping machinery, the workpiece is sandwiched between two parallel upper and lower lapping machine plates, which apply pressure and rub against each other. Lapping fluid is a mixture of abrasive and lubricating oil.
The sharp edges of the abrasive gradually scrape the surface of the workpiece during the lapping process, and the flatness of the lapping machine is transferred to the workpiece.
There are two types of lapping machinery: double-sided lapping machinery, which can process the bottom and top surfaces of a workpiece simultaneously, and single-sided lapping machinery, which can process only the bottom surface.
Usage of Lapping Machinery
Lapping Machinery is used to manufacture parts that require extremely precise flatness and parallelism. Examples include block gauges used as standards for length measurement and calibration of measuring instruments, final finishing of bearing parts that require precision, and surface treatment of difficult-to-process materials such as semiconductor wafers.
Principle of Lapping Machinery
Lapping Machinery uses the principle of three-surface abrasion, also known as Newton’s Principle, to establish a reference plane.
The three planes are rubbed against each other until they touch on all sides, and then are ground in different combinations until they touch on all sides. The principle is that when all surfaces of all combinations are in contact with each other, all surfaces are true planes.
The principle of three-sided grinding made it possible to create accurate flat and spherical surfaces even in an age without machine tools, and was used in the construction of lenses and prisms.
The principle of three-sided grinding was also used in the engineering component of Galileo’s telescope used for astronomical observations in the 16th and 17th centuries.
Lenses require smooth surfaces and accurate spherical surfaces.
The three planes in lapping machinery are the lower surface plate, the upper surface plate, and the workpiece. The upper and lower plates are finished as the standard surfaces, and the workpiece between them is simultaneously ground from top to bottom. This results in a smooth and dimensionally accurate flat surface.
Lapping Machinery Configuration
Lapping machinery is constructed using a planetary gear mechanism.
A planetary gear mechanism is a combination structure of gears. It consists of a sun gear in the center, a ring gear (or internal gear) with the same center axis of rotation as the sun gear on the outside, multiple pinions driven between the sun gear and ring gear, and a planetary carrier to support the multiple pinions.
When one of the three elements (sun gear, ring gear, and planetary carrier) is fixed and one of the two elements is driven, the remaining one element rotates differently (in number and direction of rotation) from the rotation input to the second element.
In lapping machinery, a workpiece is mounted on a pinion attached to a planetary carrier, and the workpiece is lapped by rotating the planetary gear mechanism while being clamped from above and below by a surface plate called a lap.
During the lapping process, the workpiece is ground by the orbital motion of the planetary carrier while the pinion rotates on its own axis. This is just like the movement of the earth revolving around the sun while it spins on its own axis.
Types of Lapping Machinery
Double-sided lapping machinery can be divided into 2-way, 3-way, and 4-way types, depending on the number of drive shafts.
There are four drive shafts: lower plate, upper plate, sun gear, and internal gear.
1. 2-Way System
In the 2-way system, the lower and upper plates are fixed and driven by the internal gear and sun gear. It is used for processing ceramics and metals.
2. 3-Way System
The 3-way system has a fixed internal gear and a fixed upper surface plate. It is used for processing ceramics, metals, silicon, glass, crystals, etc.
3. 4-Way System
The 4-way method is a method in which all of the drive axes are driven. 4 motors are used to match the lap lengths of the upper and lower surfaces. It is used for processing ceramics, metals, silicon, glass, crystals, etc.