While you might not need the metal components you’re making to be shiny, a lapping machine can be used to create a flat, uniform surface, improving manufacturing precision and aiding in the creation of complex shapes. The main factor in getting good results from a lapping machine comes down to the design of the lapping carrier.
How a Lapping Machine Works
The lapping carrier, sometimes called a “work holder,” holds parts inside the lapping machine, maintaining a parallel orientation between the part and the polishing surface. This carrier spins while a polishing plate passes underneath it, moving abrasives against the part surface in an orbital pattern. To keep the parts in place, a large weight or jig pushes down on the both the parts and the carrier. In double-sided lapping machines, the positioning tool has its own polishing surface. As the abrasive rubs against the part, the surface is milled, removing scratches, trash and minor manufacturing imperfections.
The shiny, flat surface left by lapping is created by replacing large scratches with smaller ones. Metal lapping is usually done with a slurry made from silica or aluminum oxide, materials commonly found on sandpaper. Like sandpaper, these materials are available in a range of grits to get the level of polish and material removal needed for the job.
How Lapping Aids in Metal Manufacturing
The milling done by these machines can be done in small, precise amounts, increasing manufacturing precision by as much as an order of magnitude over simple metal cutting. This means parts manufactured cut within a tolerance of +/-0.001 inches can then be finished to get a tolerance of +/-0.0001 inches. It can also flatten the side facing the plate, flattening sides to make perfect squares, rectangles and other geometric shapes.
Making a Carrier to Get the Results You Want
The effectiveness of lapping depends on the design of the lapping carrier. It needs to have precisely-cut holes to keep the parts aligned with the polishing plate and the outer edge needs to engage with the lapping machine with minimal slop to maintain even pressure between the parts and the polishing surface. The carrier also needs to be the right thickness to work with the parts and the machine and use the right material to preserve the parts while minimizing wear caused by the abrasives. If any of these factors is off, the parts can move around or be pushed into the plate, resulting in uneven, inconsistent surfaces.
With so many factors at work, the carrier needs to be built by a specialist. That’s where we come in. Once you submit a CAD drawing of the shape you need for your holder, we can design a plate that will work with your manufacturing process. This design is then used to make the carrier in-house and can be within a tolerance as low as +/-0.004 inches to ensure you’ll get consistent results from your lapping machine.