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.
Wet blasting can do nearly any job that is done with dry shot blasting. The defining differences are that wet blasting does so more gently and without producing dust. In addition, wet blasting can handle a small amount of oil and grease unlike dry blasting.
At Rosler, we have more than 80 years’ experience in surface finishing. While wet blasting has gained popularity recently, we’ve used this technique to provide precise, repeatable results to a number of industries over the years.
Typical Applications
With proper testing and process parameters, wet blasting can achieve numerous surface finishing goals.
A fastener with heat discoloration before versus after wet blasting.
Depending on the work piece’s starting condition and successive finishing steps, rust, scale, oxidation, road grime, grease, and oil may need to be removed. Wet blasting can accomplish a variety of cleaning applications including:
Dies and molds such as die castings and tire and glass molds.
Automotive rebuilds such as engines, transmissions, brakes, etc.
Investment castings such as boat propellers, pump impellers, housings, valve bodies, etc.
Aircraft engine rebuilds.
Various components before inspection or secondary processing.
Hydraulic components before and after wet blasting.
Work pieces with flashings and burrs must undergo deburring and deflashing. For example, firearm components require burr removal after drilling, milling, and turning. Drill bits and milling tools also require burr removal.
Despite the newest heat treatment processes, discoloration, oxidation, scale, and hard residues are found on cast and forged products as a result of manufacturing and environmental influences. Modern production methods, control and testing processes, and an uninterrupted continual processing of the cast and forged parts requires clean, light work piece surfaces.
Surface Texturing
Creating a somewhat rougher surface finish is a key step in preparation for painting, coating, and bonding with glue. Ensuring that subsequently applied coatings have a rough enough surface to adhere to improves the quality and life span of a work piece.
Examples of wet blasting applications for surface texturing include:
Preparation of automotive parts for rubber coating such as brake and engine seals.
Surface preparation to place a corrosion protection coating for screws.
Surface preparation to place a primer on airplane components such as rotor blades, stringers, and wing spars.
Orthopedic implants in which osseointegration and bone growth around the implant are encouraged. Light profiling of tibia plates, knee femorals, hip stems, and spinal implants helps promote this bone growth.
Wet blasting is ideal for stripping of paint and coatings from delicate work pieces. Processing of mineral-based construction materials such as concrete or sandstone, glass, textiles, and wood is possible with Rosler machines as well as the finishing of plastics and metals.
Landing gear includes many wet blasted components.
Shot peening is a process specially developed to improve the properties of components which are exposed to changing strains. For safety reasons, shot peening is also now absolutely necessary in the aviation and space industries. Shot peening is also essential in all industries requiring long lives for components including the automotive sector.
Wet blasting applications for shot peening are mainly used in conjunction with Almen strip N for glass beads, ceramic beads, and stainless steel shot.
Additively manufactured components before and after wet blasting.
Wet blasting is an essential technology for various post processing tasks, specifically additive manufacturing. Wet blasting cleans the 3D printed components by removing residual powder and significantly reduces their initial high surface roughness. It is capable of de-powdering and providing general surface cleaning and initial surface smoothing from Ra = 1,000 micro inches down to Ra = 40-60 micro inches (25 µm to 1–1.5 µm).
On metal AM parts the loosely sintered grains on corners are effectively removed. The wet process eliminates the worry about residual powder containment or sparking during the blasting process.
De-contamination of nuclear power plant components
Manual wet blast cabinets allows for same removal of contaminants.
Removal of small, radioactive fragments from the component surface in nuclear power plants can also be achieved through wet blasting. The process decontaminates the components to a point where they can be declassified as radioactive. Special consideration regarding the water treatment are required to meet the requirements for this application.
The Rosler Way
With a trusted partner such as Rosler, you don’t need to worry about the ins and outs of an application. Contact us to discuss your wet blasting needs and challenges and we will deliver a solution. We’ll even demonstrate results with FREE sample processing in one of our global test centers. That’s the Rosler Way.
Previous posts in the Wet Blasting Technology include:
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.
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.
Media-Induced Wear
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.
