Joint Reconstruction, Part 5 – Mass Finishing for Smooth, polished surfaces

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. Therefore, it is no surprise that mass finishing processes are utilized at practically every manufacturing stage for all kinds of orthopedic implants.

Rosler Metal Finishing has decades of experience in mass finishing. In this installment of the Joint Reconstruction Series, we will compare the various machines used to provide precise finishing for endoprosthetic manufacturers.

Examples of Mass Finishing

Mass finishing is used for a variety of joint replacement work pieces including:

  • Descaling and edge radiusing of hip stems, knee femorals, and other implants after forging or casting, e.g. lost wax or investment casting. 
  • Deburring and surface smoothing of various implants after belt or CNC grinding.
  • Final polishing of knee femorals, femoral heads, and the inside of acetabular cups to Ra = 0.8 micro inches as the last finishing stage before implantation.

Commonly Used Machines

Considering their critical function in the body, joint reconstruction implants must have a perfect surface finish without any blemishes. Even the smallest nick or dent on a component will render them unsuitable for implantation.

That is why during the various finishing operations the implants must not tumble over each other. Instead, they must be firmly attached to work piece holders so that they can never touch each other during the entire finishing process.

Compact Drag Finishers

Rosler Compact Drag

When it comes to placing the finishing touch on knee, hip, and other joint reconstruction implants, compact drag finishers are one of the most popular finishing machines in the orthopedic implant industry. They produce excellent, extremely smooth and polished surface finishes on a wide array of implants, not only with absolutely repeatable results at zero defects, but also at surprisingly low costs.

The work pieces are individually attached to workstations on a rotating carousel and are dragged through a stationary work bowl filled with media.

Features of drag finishers include:

  • Very high processing intensity.
  • Absolutely homogeneous, all-around finishing results, batch by batch without any “dead” zones.
  • Capacity for larger, highly delicate work pieces.
  • Elimination of part-on-part contact and nicking of work pieces.

Automation

Drag finishers can be easily automated by utilizing robots or specially designed material handling systems for loading/unloading the work pieces. This allows creating autonomous, fully automated manufacturing cells, which can be easily integrated into the overall manufacturing process.

Special Rotary Vibrators, Type DL

Rosler’s “DL” machines are ideal for finishing smaller production batches. They can process larger as well as smaller components such as ankle or shoulder implants, but also small volumes of knee femorals and tibia plates.

R 150 DL-2 with work piece fixture

The processing bowl on DL vibrators does not have a center dome. Instead, they are equipped with two vibratory motors mounted on the outside of the processing bowl providing the required vibratory energy. The work pieces are mounted to work piece fixtures located in the bottom of the processing bowl.

Features of the DL series include:

  • Much higher processing intensity than standard rotary vibrators.
  • Reduced media lodging in work pieces thanks to mounting the work pieces to special fixtures.
  • No risk of nicking as the work pieces do not touch each other during the process.
  • Ideal operation for low production volumes and concave shapes.

Other Mass Finishing Machines

For less delicate work pieces such as screws, trauma, spinal implants, and certain medical instruments, other mass finishing machines including standard rotary or tub vibrators or high-energy centrifugal disk finishing machines can be utilized.

Rosler Rotary Vibrator
  • Standard Rotary Vibrators – Ideal for non-delicate work pieces, these machines differ from the DL series largely because of their center dome and lack of work piece fixtures. Rosler rotary vibrators can be adapted to automated processing at any time with modular auxiliary systems for loading, unloading, rinsing, drying, and other pre- and post-finish operations.
Rosler Tub Vibrator
  • Tub Vibrators – These machines are used in applications where the biggest rotary vibrator, because of the size of the parts, might still be too small. Also known as straight tubs, these machines can accommodate large and sensitive parts. If necessary, parts can be treated in separate compartments without the risk of part on part impingement.  
Rosler Centrifugal Disk
  • High-Energy Centrifugal Disk Machines – Often used for bone screws, bone nails, and spinal hooks, high-energy disc machines offer an efficient alternative to conventional vibratory machines. They provide performance levels of up to 10 times higher than conventional vibratory equipment. Rosler has revolutionized the industry with our highly productive “Double Batch” system. Our reliable precision gap control features can be automatically or manually operated. This ensures process stability.

The Rosler Way

A manufacturing cell with two drag finishers and one robot for automatically loading and unloading.

If you need mass finishing expertise to finish your joint replacement implants, look no further than Rosler Metal Finishing. We can help you find a better way and achieve the exact finish needed every time. Contact us today to discuss your unique challenges.

Be sure to catch up on our previous posts in the Joint Reconstruction Series including:

Forge & Foundry, Part 7 – Selecting a Shot Blasting Machine for Forgings, Non-Sand Castings, and Powdered Metal Components

This installment of Rosler Metal Finishing’s Forge and Foundry Series continues with shot blasting machine selection considerations for forgings, non-sand castings, and powdered metal components.

While none of these work pieces contain sand, their surfaces may show oxidization or – in the case of ferrous metals – heavy scale/rust caused by iron oxide.

All forms of oxidization must be removed to ensure that subsequent manufacturing operations such as machining, coating, and painting are economical and efficient. Poorly cleaned work pieces may cause additional processing, premature wear on milling tools and drill bits, excessive pollution within coolant systems, and inefficient adhesion of coatings and paint.

Traces of oxidation may also impact the work piece’s functionality.

Continue reading Forge & Foundry, Part 7 – Selecting a Shot Blasting Machine for Forgings, Non-Sand Castings, and Powdered Metal Components

Joint Reconstruction, Part 4 – Comparing Surface Finishing Methods

Shot blasting and mass finishing have become indispensable technologies for surface preparation and finishing of joint reconstruction implants. Their applications range from surface cleaning, deburring, edge radiusing after forging, casting, additive manufacturing, and machining to surface preparation for different kinds of coatings, shot peening for increasing the longevity of an implant, and placing an extremely smooth, high-gloss finish on the implants before they are inserted into the body.

Rosler Metal Finishing leverages its extensive experience in the medical industry to create customized solutions and equipment for the treatment of joint reconstruction implants.

This installment of the Joint Reconstruction Series will compare the working principles and features of utilizing shot blasting and mass finishing technologies for endoprosthetic implants.

Continue reading Joint Reconstruction, Part 4 – Comparing Surface Finishing Methods

Forge & Foundry, Part 6 – Selecting a Shot Blasting Machine for Die Castings

Our Forge and Foundry Series continues with tips for selecting a shot blasting machine for die castings.

Considerations for machine selection include:

  • Are the work pieces sturdy enough to allow for somewhat more aggressive processing or must they be handled gently without any part-on-part contact?
  • Is batch processing possible or must it be continuous?
  • Which work piece handling system is best: rotary drum, troughed belt, wire mesh belt, or overhead monorail system?
  • Can the work pieces be handled by robot, etc.?

Rosler Metal Finishing builds shot blasting machines that are designed to expertly prepare the surface of delicate and sturdy die castings and everything in between. We can design a machine that is perfectly matched to your work piece and process.

Continue reading Forge & Foundry, Part 6 – Selecting a Shot Blasting Machine for Die Castings

Joint Reconstruction, Part 3 – Surface Finishing Standards

While choosing the right implant material is of utmost importance, as discussed in our previous Joint Reconstruction 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 – be it a high-gloss polish for low friction, a textured surface for easy osseointegration, or as preparation for subsequent coating, rounded edges, etc. – but also total compliance with the specified tight dimensional tolerances. The success of a joint 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 Metal Finishing is an expert in designing systems and solutions for the treatment of joint reconstruction implants utilizing shot blasting and mass finishing technologies.

Our Joint Reconstruction Series continues with an overview of the stringent finishing standards for endoprosthetic implants.

Continue reading Joint Reconstruction, Part 3 – Surface Finishing Standards

Forge & Foundry, Part 5 – Cleaning Features & Dust Precautions for Sand Castings

Our Forge and Foundry Series continues with a look at the cleaning required for sand castings and the collection of removed contaminants.  

Rosler Metal Finishing builds shot blasting machines that are equipped to prepare the surface of sand castings as well as collect removed contaminants for a consistent workpiece finish and the health of the utilized machine and personnel.

What design features must be considered in blast turbines used for the cleaning of sand castings?

Baked-on molding sand, sand cores, and scale/rust on the sand castings are difficult to remove and require turbines with a lot of fire power. Turbines with curved throwing blades, such as Rosler’s Gamma G series, have proven to be exceptionally effective since, compared to straight-bladed turbines, the curvature of the blades generates up to 25 percent higher throwing speeds!

Continue reading Forge & Foundry, Part 5 – Cleaning Features & Dust Precautions for Sand Castings

Joint Reconstruction, Part 2 – Material Standards

Joint reconstruction implants allow millions of individuals 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 Metal Finishing 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 Joint Reconstruction Series continues with an overview of the most common materials used for these endoprosthetic implants.

Material Standards

The most common materials used for joint reconstruction implants are currently titanium and titanium alloys and cobalt-chromium alloys. Both materials are very tough, corrosion-resistant, highly biocompatible, and have proven themselves to be absolutely reliable.

Continue reading Joint Reconstruction, Part 2 – Material Standards

Forge & Foundry, Part 4 – Selecting a Shot Blast Machine for Sand Castings

Building upon the information shared in our last Forge and Foundry Series post about sand casting, we now turn to the process of selecting and designing machines to specific sand casting operations.

Selecting the right shot blasting machine for your process and work piece means understanding how the work pieces and machine will interact. Here are common questions Rosler Metal Finishing receives when developing perfectly specified solutions for sand casting.

How do work piece delicacy, size, and weight influence the machine choice?

Before choosing a machine, the following questions must be asked:

  • Are the parts sturdy, allowing for aggressive processing, or must they be handled gently, without any part-on-part contact?
  • Is batch processing possible or must it be continuous?
  • Which work piece handling system is best: rotary drum, troughed belt, wire mesh belt, overhead monorail system, or heavy-duty crane or trolley on rails for extremely heavy work pieces weighing several tons?
  • Can the work pieces be handled by robot or is a custom-engineered shot blast system the best solution?

It is extremely important to find a supplier that can offer a machine that is perfectly matched to the work piece characteristics.

Continue reading Forge & Foundry, Part 4 – Selecting a Shot Blast Machine for Sand Castings

Joint Reconstruction, Part 1 – Expertise for Endoprosthetics

With more than $18 billion in annual worldwide sales, implants for joint reconstruction make up nearly 40 percent of all orthopedic product sales. More active lifestyles and increased life expectation continue to contribute to the rapid growth of this market segment.

Thanks to significant advancements on the material side and enhanced surface finishing technologies, artificial hips and knees can last more than 20 years before they must be replaced. Rosler Metal Finishing’s shot blasting and mass finishing capabilities are examples of processes and equipment that have and continue to evolve to accommodate the demand for increased endoprosthetics which are also known as orthopedic joint reconstruction implants.

These techniques play a key role in intermediate processing steps including cleaning, deburring/edge radiusing, surface smoothing, and surface preparation for coatings after casting, forging, machining, CNC grinding as well as placing the final finish on the implants before they are inserted.

Continue reading Joint Reconstruction, Part 1 – Expertise for Endoprosthetics

Forge & Foundry, Part 3 – Shot Blasting & Sand Castings

Our Forge and Foundry Series continues with a deeper look at sand castings. While more than 60 percent of all metal castings are made with a sand casting process, the specific shot blasting machines used to remove surface contaminants vary. Rosler Metal Finishing is uniquely qualified to identify the right shot blasting machine for your process and can help determine what settings and media will produce the best results with every cycle.

Sand Casting Basics

Sand casting, also known as sand molded casting, is a metal casting process using different kinds of sand as mold material. The sand is usually “glued” together with a bonding agent like clay, water, oil, resin, or sodium silicate.

A sand mold consists of two or more sections. Liquid metal is poured into the cavities formed by the mold.

Once cooled, sand molds pass through a shakeout device, where they are destroyed to extract the metal castings. The raw castings then undergo a fettling procedure, where sprews, gates, runners, and risers are separated, and coarse burs are removed.

Continue reading Forge & Foundry, Part 3 – Shot Blasting & Sand Castings

Shot Blasting and Mass Finishing Surface Finishing Experts

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