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.
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.
The family-owned business located in Kammerstein, Bavaria, works with automotive, machinery building, electronics, medical engineering, jewelry, and a variety of consumer goods customers.
Numerous functions and calibrations factor into developing a precise and stable mass finishing process. From media and compounds to work piece characteristics and processing times, successful finishing requires each process aspect to be carefully monitored and evaluated. When it comes to process water flow rates, poor drainage from the machine can cause quality control issues as well as equipment damage and costly downtime.
While simple in their function, drains play an integral role in regulating the flow of process water out of the machine. With the exception of intentional “flooding” of the process bowl for sharp work pieces, the same amount of compound and water entering the machine must be flushed out again. Otherwise, contaminants in the form of dirt, media, metal fines, and, frequently, oil will accumulate in the process water. Since this buildup can cause the finishing process to deteriorate and even collapse, mass finishing machines must have sufficient drainage!
With more than 80 years of experience, Rosler can expertly design mass finishing technology and troubleshoot issues to protect your system for the life of the machine.
Made from plastic such as polyurethane or stainless steel material, these drains must allow process water and media debris to be flushed from the system while retaining usable media mix and the work pieces.
While choosing the right implant material is of utmost importance, as discussed in our previous Orthopedic Implant Series post, the significance of optimum surface treatment throughout the entire implant manufacturing process cannot be overstated. This relates not only to the right surface finish, but also total compliance with the specified tight dimensional tolerances.
The functionality of an orthopedic implant is determined by the perfect match between the various implant components. This depends, to a large extent, on the surface treatment procedure(s).
With extensive experience in the medical industry, Rosler is an expert in designing systems and solutions for the treatment of joint reconstruction implants utilizing shot blasting and mass finishing technologies.
Our Orthopedic Implant Series continues with an overview of the stringent finishing standards for orthopedic implants.
Maintaining the correct compound and water flow rate into a mass finishing machine is essential for the stability and success of a process.
If inadequate compound and water are supplied to the machine, results will be more extreme and lead to unpredictable processing times, ineffective finishing, dirty work pieces after finishing, glazed media, and, potentially, a total collapse of the process.
Excessive compound and water flow can be equally problematic. Too much water and compound will slow down the movement of media and work pieces in the machine or cause a complete stop.
For example, in rotary vibrators the typical spiral movement of the media/work piece mix will give way to an uncontrolled shaking. In centrifugal disc machines, the rotating spinner will slip under the media/work piece mix with no movement at all.
Longer processing times, poor finishing results, and even a complete collapse of the process can occur.
For the best results and stability, Rosler understands that the flow rate of compound and water into the machine must be equal to the flow rate out of the machine.
For millions of individuals, orthopedic implants provide the ability to regain mobility and reduce pain. Just as surgical skill is required to implant these artificial joints, so is skillful construction and finish of the joint components themselves.
A leader in surface finishing for medical technology, Rosler has extensive experience in shot blasting and mass finishing a wide range of medical devices from instruments to implants used specifically for joint replacement.
Our Orthopedic Implant Series continues with an overview of the most common materials used for these endoprosthetic implants.
Popular Materials
To date, the most common materials have been titanium, titanium alloys, and cobalt-chromium alloys. Both materials are very tough, resistant to corrosion, highly biocompatible, and absolutely reliable.
Advancements in medical technology now allow for the development of Patient-Specific Implants (PSI). Specialized computer programs analyze x-rays, ultrasound, and MRI images to create surgical guides, tools, and implants tailored to the patient’s unique anatomy.
While still emerging, many medical industry suppliers have received FDA approval for PSI use. Like traditional implants, these implants must be carefully finished once created to ensure the work piece meets stringent medical safety standards while promoting patient comfort and long wear life.
The benefits of PSI use include shorter surgery times, better surgical outcomes, and cost savings.
True to its “apply innovation” tagline, Renishaw’s Medical and Healthcare Division has found great success in additively manufacturing PSI. Using CT scan-to-CAD software, one of the company’s most innovative advances is creating cranial plates using titanium powder.
When determining how to finish the implants to precise medical requirements and surgical demands, Renishaw trusted Rosler for help with mass finishing.
Trial and error are often the origin of innovation. As such, mass finishing and centrifuge technology have been advanced by building upon what worked and avoiding what didn’t.
With more than 80 years of experience, Rosler has extensive engineering knowledge and troubleshooting skills. An overview of the top three issues centrifuge water recycling systems experience along with possible remedies are summarized here. As always, trust a partner such as Rosler to consult on your specific issues.
Excess Oil in the System
Too much oil may be carried into the finishing system by the work pieces, for example, in stamping operations.
The excess oil will negatively affect the mass finishing process. The media might become “glazed” causing longer processing times and poorer finishing results. In addition, the finished work pieces may also be contaminated with oil residue.
Possible remedies include cleaning of the work pieces prior to mass finishing, for example, with an industrial washing machine, or switching to an alternative oil type that can be better emulsified by the compound for better discharge from the process water.
