Types of Metal Finishing
- Metal Plating
- Brushed Metal
- Buff Polishing
- Metal Grinding
- Metal Vibratory Finishing
- Sand Blasting
- Powder Coating
- Hot Blackening
Metal plating: machines use a chemical bath to coat or alter the surface of a substrate with a thin layer of metal, such as nickel or PTFE. The electroplating method generates an electric current to coat the substrate, while electroless plating employs an autocatalytic process in which the substrate catalyzes the reaction.
Metal plating provides several advantages as a finishing process. It can improve a product’s durability, corrosion resistance, surface friction, and exterior appearance. It is also a useful option for coating other metals. In high-volume production runs, a barrel-finishing machine is a fast and efficient plating solution. However, plating machines are generally not suited for smoothing out surface defects.
Brushed Metal: Unlike plating, brushed metal finishing is an effective method for removing surface imperfections. These finishing machines create a uniform, parallel grain surface texture to smooth out a product’s exterior. An abrasive belt or wire brush is usually employed to achieve this effect. Also, the singular direction of the belt or brush can create slightly rounded edges perpendicular to the grain.
Buff Polishing: If your project requires a smooth, non-textured finish, then a buff polishing machine may be your answer. This machine uses a cloth wheel to buff the product’s surface, resulting in a high, glossy sheen. The process is often used for decorative products that benefit from luster and smoothness.
Buff polishing machines tend to round out a product’s edges, and due to the cloth wheel’s range limits, the process is less effective for applications requiring intricate, fragile, or recessed features.
Metal Grinding: Grinding machines use friction, attrition and/or compression to smooth out a metal product’s surface. There are several types of grinding machines designed to deliver different levels of finite smoothness. For example, a ball-grinding mill is an excellent fine grinder for cement products, but may not work for more extensive smoothing projects.
Most metal grinding machines consist of a substrate within a rotating drum. Rod mills are used to make metal rods, while semi-autogenous grinding (SAG) mills and autogenous grinding mills smooth copper, gold, platinum, and silver.
Metal Vibratory Finishing: Vibratory finishing machines are used to deburr products and remove sharp edges. They position material inside a drum filled with abrasive pellets and a substrate, then apply tumbling vibration to create a uniform random texture. The machine’s cycle speed and magnitude of vibration are usually variable, allowing effective treatment for a range of small- to large-sized parts.
Sand Blasting: Sand-blasting machines are typically employed in projects requiring a uniform matte texture. The process (also known as bead blasting) forces sand, steel shots, metal pellets or other abrasives into a substrate at high speed. This results in a smooth, clean product texture, particularly in soft metals.
Powder Coating: Powder coating applies a decorative finish that is similar to paint, but with greater durability. The process involves melting dry plastic powder onto the metal to produce a textured, matte, or glossy coating. A textured powder-coating machine is also highly effective in removing surface defects.
Hot Blackening: Hot blackening machines spread a thin layer of black oxide onto a product’s surface to create a matte black finish with high abrasion resistance. It is a high-temperature process in which the product is inserted into a series of tanks containing cleaners, caustics, and coolants. Hot blackening is most commonly used in the production of automotive parts, tools, and firearms.
Choosing a Metal Finishing Process
There are a few considerations that can help you narrow your choices in selecting a metal finishing technique suitable for your project. Some helpful things to keep in mind are:
- Production speed: How quickly does the technique apply finish to the product?
- Cost-effectiveness: Certain finishing machines (such as vibratory tumblers) can be expensive, but may compensate for their price by delivering faster cycle rates
- Metal hardness: harder metals usually require more intense finishing techniques, like grinding, or may need tougher abrasives than those used on softer materials
- Potential for vulcanization