LAPPING PROCESS ON GRANITE
APPLICATION OF LAPPING PROCESS ON GRANITE
Lapping process on granite is a working process, during which workpiece and tool slide over one another on a lapping compound and are subject to continually changing direction of rotation. Stock removal occurs as a result of the rolling and sliding action of abrasive grains (aluminium oxide, silicone carbide, boron carbide) between a lapping plate (single sided lapping) or plates (double sided lapping) and the workpiece.
At present vertical double-wheel lapping machines comes with a planetary work drive system, also known as “lapping kinematics”. In this typical double-sided lapping process, carriers with gears holds the components. These form a planetary motion covering the full surface of the lapping plates. Through the upper wheel the lapping compound feeds to the machining area. The rolling lapping compound causes micro-cracks to form in the surface of the workpiece, and if several cracks meet each other, small particles break out. The lapped surface typically shows a dull, crater-like surface.
Flat Lapping is an ancient machining technique. It is a precision process or combination of processes that provide flatness, parallelism, size and surface finishes to extremely demanding tolerances. The process is a manufacturing method that employs particles of an abrasive material to remove stock from a surface. It is comparable to sanding or grinding, except that sanding and grinding use abrasives which are fixed (bonded abrasives). Whereas lapping employs abrasives which suspends in a liquid carrier, and are free to move about.
Lapping and fine grinding are processes find application where the surface finish, flatness, or parallelism of the work piece must be held to very close tolerances. Lapping can achieve flatness rating of one millionth of an inch (0.000001″), parallelism tolerances of ten millionths of an inch (0.00001″) and surface finishes to 0.6Ra. Using special handling and tooling techniques.
Abrading Methods can achieve flatness tolerances of 12 millionths (0.000012″). The parallelism is of fifty millionths (0.00005″) and flatness of 1Ra on a production basis. Besides, we can achieve tolerances at the limits of the lapping process on a case-by-case basis. Also, abrading methods can provide lapping, free abrasive machining, flat honing, fine grinding, polishing, burnishing and precision fine grinding. Similarly it provides special deburring and cleaning techniques to process your flat surfaces. Also, with over 30 years of experience, special equipment and proprietary processes, Abrading Methods can produce flat and parallel surfaces from thousandths to millionths of an inch, in production quantities, at an economical cost.
We can define lapping as a machining process that uses free (unfixed) abrasive to machine the surface of a given part or material. Common abrasives in lapping, such as aluminum oxide and silicon carbide, combines with a liquid, called “vehicle”, to create slurry. In the case of single-sided lapping, slurry pumps on to a spinning plate. This carries the slurry beneath a work piece that is held in place by a hold-down pad. In double-side lapping, the work pieces rests within a carrier. This is a special gear with holes accommodates the work piece. Consequently, the work piece is sandwiched in-between an upper and lower lapping plate. The slurry is fed in the lapping plates through a series of holes drilled into the upper plate.
The lapping process on granite has the ability to improve the flatness, surface finish, and parallelism of the work piece. Therefore, being able to control the thickness size to within millionths of an inch. Besides, this procedure is more superior to standard grinding methods, and it allows for tighter tolerances, improved finish, and parallelism. More recently, processes have been developed that allow the abrasive to be fixed within the lapping plate. As a result, this provides a more aggressive machining action thus removing excess stock faster. Besides it is without compromising flatness, parallelism, or the surface finish.
- Performed with loose abrasive
- Stock removal caused by rolling and sliding action of abrasive grains
- Lapped surface is dull and crater-like
- There is no recycling of material and lapping compound
- Lapping compound contaminates work parts and require cleaning
- Lapping speeds are generally less than 1 m/s
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