Due to their precision, efficiency, and economy, mass finishing and shot blasting are an indispensable part of the finishing process for a wide variety of orthopedic implants in different manufacturing stages.
These flexible machines can handle general cleaning; deburring; surface smoothing after casting, forging, stamping, machining, and heat treatment; surface preparation for polishing or coating; and the placement of the final finish on all kinds of implants and medical devices.
With an experienced partner such as Rosler, these processes are also capable of adapting to emerging trends with proper testing and processing trials.
Evolving Technology & Outlook
Orthopedic implant manufacturers are at the cutting edge of medical technology. New materials and manufacturing techniques and technologies are constantly evaluated to improve the performance and longevity of the implants and reduce the manufacturing cost. Two examples are the increased use of ceramics as base material or coating and additive manufacturing.
Specific mass finishing applications are developed through processing trials. Once defined, users should not deviate from the determined machine settings unless necessitated by work piece or process changes.
Rosler partners with clients to provide testing in our global Customer Experience Centers to demonstrate our capabilities on a specific work piece and to calibrate machine settings. Determining the exact machine settings requires considering and testing multiple factors.
Vibratory Systems
The most common drive systems in mass finishing are vibratory. This refers to actual finishing machines such as rotary, tub, and linear continuous flow vibrators as well as auxiliary equipment like screening systems, vibratory conveyors, buffers, etc.
In all of these cases, the speed of the vibratory motor or the electric motor driving the imbalance unit(s) may have to be adjusted as well as the setting of the imbalance weights.
Vibratory weight plates
The angle between the upper and lower imbalance weights determines the movement of the media and work piece mix within the machine.
The number (mass) of imbalance weights determines the processing intensity (amplitude). More weights produce higher intensity while fewer weights deliver lower intensity.
Vibratory motor diagram
Setting Imbalance Weights
The movement of the media/work piece mix is always opposite to the motor direction. Typically, the motor runs clockwise and the media/work piece mix runs counter clockwise.
In some instances, the motor can run clockwise and counterclockwise including the Rosler “R” machines and gate clearing in Rosler “Euro” machines.
Half-circle metal plate weights on the top and bottom of the motor must be positioned with respect to each other. For a basic setting, the bottom weight plate must be turned 90 degrees forward of the top weight plate, in a basic setting.
Imbalance weights locations and settings within a vibratory motor
When setting imbalance weights, it is important to understand the impact of changes. For example, increasing the lead angle will make the media/work piece mix travel around the work bowl faster. Decreasing the lead angle will have the opposite effect, slowing movement.
Typical lead angles range from 70 to 120° and can be observed by checking the gauge on the top of the motor shaft.
Vibratory motor lead angle gauge
Within the imbalance weights, the top weight controls the travel speed of the media/work piece mix around the work bowl. Adding additional weights to the top will increase the travel speed while decreasing the spiral speed in the work bowl.
The top imbalance weight controls media and workpiece speed around the work bowl as represented by the red arrow while the bottom imbalance weight controls the spiraling speed of the work bowl contents.
The bottom weight controls the spiral speed of the media/work piece mix in the work bowl. Conversely to the top weight, adding additional weights to the bottom will increase the spiral speed but also decrease the travel speed around the work bowl.
Action Points
Regularly checking a mass finishing machine’s settings including motor speed(s), setting of imbalance weights, work station angles, etc. to ensure they are as initially established will produce better results and protect the systems ROI.
Additionally, if repairs require drive motors to be disconnected, make sure that they are rewired correctly and are not running in the wrong direction.
If the machine settings must be changed, carefully follow the instructions in your operator’s manual or consult the manufacturer for assistance.
If not already integrated, installation of a frequency inverter for precise setting of the drive speed of your machine may be available as an upgrade, providing additional control and oversight.
The Rosler Way
Rosler goes beyond developing mass finishing machines to provide operational insight and guidance for the lifetime of our machines as well as consumables and service. Contact us to discuss your needs and our capabilities.
During more than 80 years in business, the Rosler team has gained extensive experience in shot blasting and mass finishing for a variety of industries.
In addition to the machinery and consumables we provide, our Customer Experience Centers enable us to demonstrate Rosler’s expertise by processing your samples with settings and requirements tailored to your needs.
Sending your work pieces to one of our 11 test centers around the world is an important step in achieving the perfect surface finishing process.
Learn what to expect from Rosler’s Customer Experience Centers and get the most out of your partnership with Rosler from Sales Representative and Interim Product Manager of Turbine Blast Equipment Zack Murray and Mass Finishing Product Manager Michael Salyers.
What to Expect as a Customer
To achieve optimal processing results, we carry out sample processing step-by-step.
With an emphasis on finding a better way, our process includes:
Growing utilization of additive manufacturing for volume production of plastic components has increased the demand for cost-efficiency and high-quality surface finishes. That’s why AM Solutions, a brand of the Rosler Group, has further expanded its product portfolio with the development of a new media type for post processing of plastic components.
Designed specifically for work pieces printed with MJF and SLS powder-bed-based technology, AM Solutions’ new media permits the safe, cost-efficient finishing of 3D printed components with different shapes and sizes in one single process step and with absolutely repeatable results. This eliminates the time-consuming and costly media changes for different processing stages.
In combination with an understanding of respective printing processes, the new media mix generates a perfect, finely structured, and highly homogeneous surface finish.
Blast cleaning is uniquely capable and efficient at delivering the pre-coating surface preparation required for components that must be able to withstand severe ambient conditions including heavy equipment for construction and mining, agricultural machinery, transportation and material handling equipment, and railway equipment and rolling stock.
Based in Enschede, Netherlands, the company designs and produces numerous products including placement systems for container pads. Its customers largely work within the material handling, offshore, and transportation sectors.
Even if the finishing media and compound/water are managed perfectly, without a well-functioning machine a mass finishing process is doomed to fail. Focusing on a few essentials will ensure that a mass finishing machine is performing as intended.
From machine settings to preventative maintenance and troubleshooting tips, Rosler has the experience and insight to keep mass finishing machines running efficiently.
The Right Machine Settings
The speed at which a machine is running is critical to the success of a finishing process.
If the machine is running too slow, the finishing results, deburring/edge radiusing, surface grinding, etc., might not be achieved at all or only after excessively long processing times.
If the machine is running too fast, the work pieces may be damaged by scratching, nicking, or bending. Excessive speeds will also cause the media to wear much faster without the benefit of shorter cycle times. Beyond speed, other machine settings must be taken into consideration based on the specific machine type.
Like mass finishing, shot blasting is an exceptionally versatile surface treatment technology. Its applications range from general cleaning after casting and forging to shot peening and, even, cosmetic blasting for placing a fine, matte finish on the work pieces.
For shot blasting orthopedic implants, Rosler recommends mainly air and occasionally wet blasting systems. In each process, blast media is accelerated by compressed air and thrown at the work pieces through a blast nozzle, creating an extremely precise blast pattern compared to turbine blasting. Another advantage of air blasting is that it can be used with metallic, mineral as well as organic blast media.
Air blasting and wet blasting schematics
These attributes and many more make this surface finishing method particularly useful in the medical industry.
Examples of Shot Blasting
Shot blasting is an impact system in which small metal or mineral pellets are thrown onto the surface of a work piece at speeds of 200-800 feet/second. The impact on the work piece surface produces the desired cleaning, peening, or texturing effect.
For medical applications, mainly air and wet blast systems are used which generally make a surface rougher. The smoothest finishes achieved with shot blasting are about Ra = 16-32 microinches (= 0.4 to 0.8 μm).
The family-owned business located in Kammerstein, Bavaria, works with automotive, machinery building, electronics, medical engineering, jewelry, and a variety of consumer goods customers.
Unlike dry blasting that only uses a solid abrasive media, wet blasting processes use a slurry of water with the shot blasting media. This greatly cushions the impact energy on the work pieces, providing gentler, yet effective results for delicate work pieces. The achieved surface finish and appearance will also differ between wet and dry processes, even when the same media type and size are used.
With more than 80 years of experience worldwide, Rosler can supply both the machines and media best suited for your wet blasting needs.
Common Media Types
As long as it is heavier than water and not water soluble, practically any media used for dry blasting can be used for wet blasting.
It is important to consider the usefulness of the media compared to its cost. While a cheaper or longer-lasting media may be available, it may also require additional processing time to accomplish the desired surface finishing. Selecting the most appropriate media for your process requires balancing initial costs with overall results.
Mass finishing is a highly versatile finishing technology that can be used for a wide variety of different surface treatment operations including those in the medical industry. As a result, it is no surprise that mass finishing processes are utilized at practically every manufacturing stage for all kinds of orthopedic implants.
With decades of experience, Rosler leverages mass finishing technology and develops equipment to meet the tight tolerances required for orthopedic implants.
Common Finishing Processes
Mass finishing is a grinding system, utilizing the pressure between the media and work pieces, combined with the constant “rubbing” of the media against the work pieces. This generates a grinding and polishing effect, leaving a smooth surface finish that can be as low as Ra = 0.8 microinches (0.02 μm).
For the comfort of patients and effectiveness of the components, orthopedic implants must be finished to precise specifications.
