Precision lapping is a finishing process used to manufacture dimensionally accurate products that require extremely tight tolerances of flatness, parallelism, thickness, or surface finish.
Lapping is an acronym that is short for Loose Abrasive Process. It is a free abrasive machining process that removes material at a controlled rate to produce smooth, flat surfaces that can achieve a flatness rating of one millionth of an inch (0.000001"), parallelism tolerances of ten millionths of an inch (.00001") and surface finishes to 0.6Ra. using special handling and tooling techniques.
Precision Lapping Process
The precision lapping process uses micron-sized abrasive, low pressure, and low speed, to remove material slowly and accurately. The loose abrasive particles are suspended in oil or water-based slurry and spread across the surface of a flat, horizontal rotating plate to serve as the cutting mechanism. Precision lapping is generally a wet process that removes between 5 microns and 500 microns of material from each side of the part. It is an averaging process with the greatest material removal occurring at the highest points of the part's surface contact the plate with an objective of producing a uniformly smooth and typically flat surface.
Standard lapping produces a grey matte finish, but the equipment can also be used to polish surfaces to a shiny or mirror finish, depending on the material of the part and the abrasive used. Light “micro-scratches” may be visible on lapped surfaces. Larger sized micron abrasive with harder compound will produce more micro-scratches in addition to deeper scratches. Micro-scratches produced with small micron aluminum oxide abrasive will typically be less than .000001” (.025 micron) deep and not measurable with a profilometer.
The process for each part is customized and determined by a variety of factors including the type of material being processed, speed of the plate, plate hardness and temperature, pressure on the part, size, and type of abrasive.
Precision Lapping Machines
There are various size lapping machines with varying plate diameters. There are single side and double side lapping machines that operate on the same basic principles.
· Single side lapping machines lap one side of a part. The parts being lapped are held against the surface of the lapping plate by their own weight or by a pressure plate with hand weights or pneumatic down pressure. This process allows us to process parts up to 40 inches in diameter.
· Double side lapping machines are capable of lapping both sides of a part at the same time. The parts being processed are placed in work holders (carriers) that mesh with inner and outer ring gears to provide a random planetary motion. The double side process is best used in applications that require both sides of a part to be lapped to achieve very tight parallelism, flatness, and thickness specifications.
Lapping is a batch loading process generally used on flat surfaces, not rounded parts
It is a passive grinding process using low pressure, low speed, and low removal rate
Micron-sized abrasive particles are used
Lapping is nearly always a wet process
Movement of the lap plate or the parts are required
The lap plate is usually softer than the parts
The retaining ring is as hard or harder than the lap plate
Minimal material is removed from each side of the parts
Trilap Precision Finishing
Trilap has become the preeminent leader in precision lapping and grinding for aerospace, defense, medical, and industrial applications. No one else can provide a higher level of precision or deliver it as fast. Click here for more information about our services or contact us with any questions.