During mass finishing, the process water injected into the finishing machine is contaminated with the chemical ingredients of the compounds, fines from the grinding or polishing media, and metal fines from the work pieces.
In case of ball burnishing, when acidic or alkaline compounds are used, the process water can also contain dissolved metals or be alkaline or acidic. Or, for example, when the work pieces are covered with oil from machining or stamping operations, the water can even be contaminated with oil.
Rosler has developed a series of closed-loop, water circulation systems using centrifuge technology to remove these contaminants regardless of their origin and allow clean process water to be reused and/or safely discharged. In addition to offering more effective work piece processing, cleaning process water saves money and the environment through reduced consumption, compound usage, disposal costs, and regulations.
“Glazing” occurs when the surface of the media becomes contaminated with metal fines and other debris from the work pieces. As a result, the media becomes very shiny and frequently looks like a piece of aluminum, brass, steel, zinc, etc.
Because glazed media completely loses its original surface properties, it no longer has any grinding effect. Instead, glazed media creates a sort of uncontrolled burnishing. It also retains dirt and other particles which are then deposited on the work pieces.
The image above depicts (from left) media states include clean, heavily glazed, partially cleaned, and fully cleaned.
Rosler has more than 60 years of media production experience. In that time we’ve seen—and corrected—countless examples of ineffective surface finishing as a result of media glazing.
When expertly combined by an experienced finishing expert such as Rosler, this method can achieve precise and repeatable results on a variety of work pieces from a wide range of industries.
A general understanding of the essential technical elements of a wet blasting machine will help you select a machine for your specific needs as well as prolonging the efficiency and life of existing wet blasting equipment.
Before the “dirty” process water coming from a mass finishing operation can be discharged to sewage, it must be cleaned to meet the legal discharge limits for hazardous materials. Likewise, for cycling the water back to the mass finishing process, the process water must also be cleaned. Uncleaned process water would cause a mass finishing process to collapse very quickly.
Rosler has more than 80 years of surface finishing expertise. In that time, we’ve developed countless efficiencies in both the design of our equipment and the processes they support. Centrifuge technology has long been an effective and cost-efficient tool, not only for cleaning the process water, but also for reusing it for the actual mass finishing operation.
Previous Cleaning Methods
To a large extent, this technology has replaced traditional waste water cleaning methods. Until recently, the most common cleaning systems for mass finishing applications were settlement tanks and flocculation (“floc & drop”) systems.
Unlike dry blasting in which only solid abrasive media is used, wet blasting processes use a slurry in which the media is embedded in water. This greatly cushions the impact energy on the work pieces, providing gentler, yet effective results for delicate work pieces.
As the utilization of wet blasting increases, Rosler reminds manufacturers to review their traditional, dry shot blasting applications and consider if wet blasting could provide additional efficiencies, reduced costs, and better results.
Understanding the Differences
As in any surface finishing process, the starting condition of the work piece, its material composition, shape, and final finish largely dictate which finishing application is most appropriate. Understanding how the application changes the work piece is a key consideration.
As a result, media wears down over time, losing its shape, size, and effectiveness. Known as undersized media, this worn media must be discharged and replaced with fresh media to ensure proper processing and safety.
Whether a process uses ceramic, plastic, or polishing and drying media, Rosler stresses the importance of monitoring media levels and the mix of new and worn media for precise and safe mass finishing results.
Mass finishing machinery is a major investment for most companies. Proper maintenance and preventative repairs over the life of these useful and necessary machines will greatly improve the return on such investments, drive productivity, and extend the working life of the equipment itself.
Rosler stresses the need to regularly inspect the linings of vibratory tubs and troughs to identify repairable issues before permanent damage occurs.
To effectively finish work pieces, media must be matched to the specific finishing task and initial state of a work piece. For example, media used for deburring/edge radiusing and surface grinding can be very abrasive. If not properly protected by a suitable wear lining, the steel construction of a work bowl would be completely worn through in a few hours by contact with the media and work pieces.
Thanks to its many technical advantages and “gentle” application, wet blasting is a versatile and fast-growing segment of the shot blasting field. Achieving precise, repeatable results with any wet blasting process requires understanding both its principles and real-world uses.
With decades of experience and the latest in engineering expertise, Rosler understands how to develop efficient wet blasting machines and consumables. Learn more about wet blasting technology as we begin our five-part Wet Blasting Technology Series.
How Does Wet Blasting Work?
Wet blasting is a water-based method of shot blasting utilizing abrasives that are particularly suited for the finishing of delicate, precision-produced parts.
Maintaining the right ratio of media to work pieces is essential to achieving precise, repeatable results in mass finishing processes where work pieces and media loosely tumble in the processing bowl.
Ensuring that the work pieces are properly embedded in the media allows the media to perform its designated grinding or polishing function as well as cushioning the work pieces from damage caused by part-on-part impingement.
The standard ratio of media to work pieces is around 3-to-1 by volume – meaning that the mix is 3 parts media to 1 part of work pieces – but the exact ratio varies based on the aggressiveness of finishing required as well as the work piece’s material, shape, size, weight, and delicacy or lack thereof.
For transmission components like gears and shafts, shot peening has become an indispensable step in the overall manufacturing process.
With the RWT swing table machine, Rosler developed a modular equipment concept that can be easily adapted to different technical requirements and offers a maximum in process stability paired with absolutely repeatable peening results and high cost efficiency. One of the numerous customers within the automotive industry utilizing the RWT is an Asian automotive supplier.
As part of a capacity expansion for minivan transmissions, this customer increased annual production to 40,000 units and decided to carry out the required shot peening operation in-house instead of subcontracting it to an external job shop.
The specifications called for a system that can handle around 560,000 single work pieces per year, including 15 different types of gears and shafts. Each work piece type required the development of a specific peening program based on drawings and various work piece materials.