Mass finishing, trowalizing and vibratory finishing are different terms that describe the same technology, namely the mechanical surface finishing of components. This technology is using polishing or grinding media (frequently also called âchipsâ or âtumbling stonesâ) and, usually, a liquid additive (a mix of water and a chemical compound) in special equipment such as vibratory, centrifugal force or drag/surf finishing machines. A similar process is tumble finishing, in which the material is removed without vibration and only by a rotational movement.
During mass finishing process, the machines set the media and work pieces in motion causing a constant ârubbingâ action. The resulting â more or less pronounced â abrasion removes material from the work piece surface and, thus, produces the desired deburring, smoothing, polishing or cleaning effect.
Mass finishing is employed across a wide range of industries. For example, it is used for treating single large components, such as automotive wheels or large ship propellers. But it is equally effective for the consistent, economical and easily controllable surface finishing of large batches of smaller work pieces.
How does mass finishing work?
In the most common finishing machines the motion of media and work pieces is induced by vibration: Together with suitable grinding or polishing media, made from plastic or ceramic, the raw, untreated work pieces are placed into a round or rectangular processing bowl. An electric motor with attached imbalance unit(s) induces a vibration into the bowl and causes the constant rubbing of the media against the work pieces. This results in the removal of material from the work piece surface. Through the addition of, mostly, liquid chemical compounds additional surface effects like corrosion protection, degreasing or general cleaning, can be achieved.
What equipment is used for mass finishing operations?
The most popular mass finishing machines for processing large volumes of non-delicate work pieces are rotary vibrators, which are available in different versions and sizes. They allow the finishing of practically all work pieces made from a variety of different materials, provided they are not too big and not fragile. For processing long, relatively bulky work pieces tub vibrators with a rectangular processing bowl are available. Compared to vibratory equipment special mass finishing systems like centrifugal disk finishing machines as well as drag and surf finishers offer a significantly higher processing intensity. They allow the finishing of difficult-to-machine materials in surprisingly short cycle times. For example, surf finishing, optimized by Rösler, is the most intensive mass finishing technology available in the market. Compared to vibratory systems, surf finishing is up to 50 times more intensive. Another benefit of drag and surf finishing is that the work pieces do not touch each other during the entire finishing operation. This is especially advantageous for treating extremely delicate components such as orthopedic implants and jet engine parts.
The most common finishing objectives
Deburring
Many users employ the mass finishing technology primarily for deburring, i.e., the removal of sharp edges, material overflow in the form of flashes and general edge imperfections produced by previous manufacturing steps. Most of the time, further downstream manufacturing operations are only possible after the work pieces have undergone a mass finishing operation, frequently called âtrowalizingâ. With suitable grinding & polishing media and compounds practically all materials, even work pieces made from plastic, wood and rubber, can be treated.
Polishing
Polishing is one of the most important applications for mass finishing. The polishing goals can be of a purely esthetic nature, but they can also be functional, for example, the reduction of friction. Polishing is characterized by minimal abrasion, which removes very little material but makes the work piece surface extremely smooth and shiny. Particularly glossy surfaces are achieved by utilizing different media in combination with special polishing agents like pastes in multi-step processes.
Edge radiusing
Edge radiusing, a particularly intensive type of deburring, is another important application for mass finishing. Sharp edges as well as burs are usually generated in previous manufacturing operations. Radiusing (rounding) such sharp edges produces many positive effects: It helps to reduce the wear of down-stream manufacturing equipment and reduces the risk of injury during assembly operations. Furthermore, it increases the usable life of the respective components. And, if the components are coated, it improves the durability of the coating.
Surface cleaning
Removal of dirt, oxide layers and other contaminants from the work piece surface. Like other surface treatment operations, cleaning is in many instances an essential pre-condition for safe and effective downstream manufacturing operations. For example, deep-drawn components are covered with oil and grease and must be cleaned, before they can be further processed. Mass finishing is also used for somewhat unusual applications like cleaning cutlery in large-scale gastronomical operations or cleaning and polishing of coin blanks.
Which industries are using the mass finishing technology?
The mass finishing technology is at home in nearly all industries. Among others it is used in:
- The automobile industry for deburring, surface smoothing and polishing of transmission components, piston rings or bearing parts; also for surface refinement of visible items and automotive wheels.
- In the aerospace industry for deburring and smoothing of turbine blades and other high-precision components.
- In medical engineering for polishing orthopedic implants, like hip and knee joints, and surgical instruments.
- In machine building for surface refinement of tools, bearing components and machinery assemblies.
- In the jewelry industry for smoothing and polishing trinkets made from precious metals.
- In electronics for surface treatment of housings and electrical contact areas.
