Achieving the desired surface conditions in a mass finishing process requires the machinery, consumables, compounds, and process water to work together in a balanced manner. Independent of the other process elements, the process water itself must be evaluated for hard and soft water issues.
Rosler has more than six decades of experience designing mass finishing machinery, supplying consumables and compounds, and developing processes. Understanding the ramifications of too hard or too soft process water is a key to our success.
Classifications and Measurements
Depending on its geological source, the water used in mass finishing processes may have varying mineral content levels, specifically calcium and magnesium carbonates, bicarbonates, and sulfates. A high amount of mineral content is used to classify the water as “hard”, whereas low mineral content classifies it as “soft”.
Establishing and maintaining an effective and cost-efficient process water recycling system requires consideration of a few essential points. Without the proper compounds, additives, and monitoring, even a well-designed piece of centrifuge technology is bound to falter and, eventually, fail.
Rosler has extensive experience in mass finishing, including designing and manufacturing equipment, fine-tuning processes, and supplying the right consumables for a variety of processes. With our knowledge, preconditions and consumables can be calibrated for maximum process efficiency.
Special Recycling Compounds
Mass finishing compounds fulfill numerous tasks such as degreasing/de-oiling work pieces, burnishing/brightening surfaces, and providing a temporary corrosion protection. Above all though, the primary task of the compounds is to keep the media and work pieces clean to achieve the desired finishing goals and keep the mass finishing process stable.
Combining the direction of rotation and centrifugal force, Rosler’scentrifuge technology takes advantage of the weight difference between the liquid phase and the solids in the process water to separate “dirty” solid particles from clean, reusable process water.
The effectiveness of this technology lies in the centrifugal force that is created. For example, a modern fighter jet develops a G-force of about 10-15 while a high-speed centrifuge drum generates a force of more than 2,000 G.
The physics of centrifuge technology combined with mass finishing equipment creates efficient and ecologically sound manufacturing processes, albeit with some key limitations.
Collection by Force
The solids, primarily consisting of media and, to a lesser degree, of metal fines from the work pieces, found within “dirty” process water are heavier than the water itself. As the drum spins, heavier solids are deposited on the drum wall in the form of sludge, whereas the lighter-weight liquid remains on the inside of the drum. With the addition of special cleaning additives known as flocculants, even oil carried into the mass finishing process can be removed from the process water.
Media selection is key in any surface finishing process since these consumables are essential “precision tools” required to achieve the specified finishing results.
Whether you are developing a new mass finishing process or changing process parameters including different work pieces, process times, and requirements, partnering with an experienced expert will help you in evaluating all process parameters.
With decades of experience developing mass finishing machines and manufacturing media and compounds, Rosler is an excellent source for guidance. In some cases, pre-tumbled media may be suggested.
What is Pre-tumbled Media?
After production, some types of pre-polishing and polishing media are pre-tumbled by the manufacturer. This process breaks sharp points and corners off individual media pieces to create smoother edges.
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.
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.
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.
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.