Where Does the Word “Polishing” Come From? It Has Little to Do with Polishing Cars!

What is polishing?

• A process for creating a reflective surface
• The polish is normally created by using fine-micron or sub-micron abrasive particles in combination with a liquid.
• Polishing is a “wet” process.
• The polishing process often uses a pad to hold the abrasive, so polishing cannot be a “loose abrasive process”.
• Very little material is removed during polishing, usually measured in microns.
• The surface finish of the workpiece must be of high quality before polishing, so the pre-polishing process is often a “lapped” surface.

Functions of polished surfaces

• Allows high-pressure gases and liquids to be sealed
• Cosmetic purposes
• Allows optical flatness measuring instruments to be used
• Reduces the amount of surface and subsurface damage
• Provides better uniformity of surfaces that require epitaxial processes or deposited materials
• Creates sharper edges on cutting tools

Types of polishing

• Soft or hard pads with a conventional or special abrasive slurry
• Soft or hard pads using a diamond abrasive slurry, which can be water-based or oil-based
• Hard pads with diamond compound and lubricant
• Diamond slurry polishing with a composite plate
• Diamond slurry polishing with a metal plate
• Fixed abrasive layers (trapped abrasive) and lubricant

Lapping vs. polishing

Lapping

• Matte, non-reflective surface (dull)
• Multidirectional lay pattern
• Component function (coating)

Polishing

• Reflective surface
• Typically the 2nd step
• Component function (sealing)
• Cosmetic appeal
• Light band inspection

How does polishing work?

• Polishing often uses a polishing pad and a water-based slurry to create the reflective or clear surface.
• A flawless, scratch-free surface finish is critical on polished surfaces.
• To create the required surfaces, polishing slurries are often corrosive. That is why polishing systems may be equipped with exposed stainless steel components such as fittings, rings and plates.
• In addition, some polishing applications also require a thorough water rinse at the end of the processing cycle to remove the polishing compound and avoid “staining” the surface. This is another reason why stainless steel is needed.
• Polishing pads are usually classified as either “soft” pads or “hard” pads.
• Lapping and polishing systems are very similar in most respects.
• However, since polishing is usually done with a pad and slurry, the surface tension is quite high compared with lapping.
• In addition, a polished part has a much higher surface tension than a lapped part.
• Based on the points above, polishing systems may need more powerful drives.

Polishing lathe

Polishing is the name given to removing a small amount of material. The aim is to smooth the surface. “Polish” refers to the polishing compound used and, where applicable, to the result achieved by the polishing process.

When polishing, polishing grains are drawn across the surface with a certain amount of pressure. The polishing grains are contained in a paste, the polish. The actual process corresponds to grinding, but polishing is meant to remove as little material as possible. Removing material next to scratches makes them invisible. The reduction in material thickness is a necessary side effect.

Polishing can serve two purposes. On the one hand, a smooth surface has less friction, which can be important for mechanical components. On the other hand, a smooth surface reflects incident light evenly, which is perceived as gloss. In industrial polishing of brass, for example, polishing serves to produce surfaces that are as uniform as possible, so that the workpiece is optimally prepared for downstream processes such as electroplating.

For special plastics and polymers (e.g. PMMA), so-called thermoplastic processes are used in polishing. The roughness peaks of the surface structure are plastically and partially plastically deformed and thus leveled (also called burnishing). Depending on the type of process, there is a very small to small amount of material removal (gloss grinding) as well as filling of recesses. Because of its smoothness, the resulting surface is often glossy.