Category Archives: Mass Finishing

Part 2 – Mass Finishing or Shot Blasting, Which Technique is Best for Medical Instruments?

The medical industry is constantly looking for better, more suitable materials that will offer greater performance and longevity for medical devices, implants, and instruments while simultaneously searching for more efficient manufacturing technologies.

When it comes to surface finishing, such newly developed materials and manufacturing processes can pose considerable technical challenges. That’s why close cooperation between the medical device manufacturers and qualified surface treatment experts is essential during the development and prototyping phase.

In our last medical instrument blog, Rosler Metal Finishing discussed the surface finishing requirements for medical instruments. This blog will dive deeper into the techniques used in surface finishing and answer the question: What is the best type of surface finishing for medical instruments?

The short answer is a combination of mass finishing and shot blasting. Guidance for a surface finishing expert can help determine the best process – typically a series of processes – for a specific medical instrument.

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Spinal Implants, Part 1 – Surgical Specifications

Technological advances in medical equipment and implants have driven worldwide spinal implant sales to $10 billion annually.

Like orthopedic implants used for joint reconstruction and the surgical fixation of a bone fracture, spinal implants are subject to very specific and strict surface finishing requirements.

Mass finishing and shot blasting play a key role in creating the right finish for spinal implants, not only for intermediate surface treatment after forging, casting, machining, additive manufacturing, etc., but also for placing the final surface finish before implantation.

Rosler Metal Finishing has extensive experience in surface finishing spinal implants using mass finishing, shot blasting, and a combination of both methods.

In a series of posts, we’ll analyze the specific surface finishing requirements for spinal implants based on their functional and performance characteristics and describe the respective mass finishing and shot blasting equipment and methods available to fulfill these requirements.

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Part 1 – Surface Finishing Requirements for Medical Instruments

Rosler Metal Finishing understands that medical instruments are subject to stringent quality standards. Whether during an office visit or a complicated surgery, material defects or malfunctions may create dangerous and even fatal consequences for patients and healthcare workers alike. Providing precise and durable surface finishes  for work pieces used in the medical industry is one of our passions.

In a series of blog posts, we’ll discuss the various technologies used for finishing the surface of medical instruments and how mass finishing and shot blasting play a key role, not only as intermediate steps but also for placing the final, finishing touch on these work pieces.

We begin with a basic question: What are the surface finishing requirements associated with medical instruments?

Materials Matter

Medical instruments are exposed to frequent use and subject to highly corrosive atmospheres caused by frequent sterilization in a steam pressure chamber, exposure to chlorine wipes, and ultrasonic cleaning. They must never fail. To minimize wear and prevent corrosion most medical instruments, especially surgical tools, are made from tough, slow wearing, corrosion-resistant, high-performance metal alloys including austenitic stainless steel, titanium, or cobalt chrome.

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Achieving Specific Finishes for Trauma Implants

In our last trauma implant blog, Rosler Metal Finishing discussed the materials used in trauma implants. From hip replacements to cranial plates, there are numerous uses for trauma implants; each with its own unique surface finishing needs and requirements.

Trauma implant manufacturers must achieve the necessary surface finish to ensure patient safety and best results. These finishing requirements can range from simple cleaning or deburring to surface smoothing and high-gloss polishing.

This blog will answer the question: What techniques are used to finish off trauma implants?

What types of finishes are used?

Trauma implants are subject to multiple finishing operations throughout the manufacturing process. After manufacturing steps including forging, blanking, machining, and thread cutting for screws, the workpieces usually undergo a surface cleaning (descaling, de-oiling), deburring, edge radiusing, or surface grinding operation, before they receive their final finish.

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The Importance of Material Selection in Trauma Implants

Rosler Metal Finishing understands that trauma implants and medical devices are subject to stringent quality standards. Any material defect or malfunction can have catastrophic consequences for a patient. That’s why we take our work in the trauma implant field very seriously.

Also known as osteosynthetic implants, trauma implants include pins, screws, and plates used to surgically fix a bone defect. Implant manufacturers must select the right material and attain the required surface finish to ensure patient safety and best results.

Spinal Rods & Screws

In a series of blog posts, we’ll answer the most common questions about trauma implant materials and finishes.

We begin with a basic question: What materials are used in trauma implants?

The answer, in short, is usually stainless steel or titanium.

Does the material performance affect the selection?

In order to select the best material, trauma implant manufacturers must understand the specific performance attributes of the implant they are creating. Implants are subject to very strict performance and reliability standards. Selected materials must act as bone stabilizers and healing support while meeting the following guidelines.

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Optimal Media Mix, Part 2 – Understanding Media Consumption

As we established in Part 1 of this seriesidentifying and maintaining an optimal media mix is essential to realizing optimal mass finishing results. Rosler Metal Finishing  understands that our equipment must work in tandem with media to provide you with the desired finishing results.

Understanding how your machine, the work pieces it is finishing, and the selected media will interact is key to delivering an optimal finish each cycle. Doing so requires understanding media consumption factors in order to maintain an optimal media mix.

What are the Factors of Media Consumption?

Media consumption and wear rates depend on ten key parameters. These rates change if even one of the parameters below change. Therefore, quoted wear rates and cut rates are relative values only.

Media usage can only be estimated, the actual consumption can only be determined by the end user under exact process conditions.

Parameters affecting media consumption include:

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Optimal Media Mix, Part 1 – Identifying and Maintaining Proper Levels

The best mass finishing equipment is useless without the proper media. That’s why the experienced engineers at Rosler Metal Finishing pair their quality equipment with the right type and amount of media to achieve consistent results.

Understanding how your machine, the work pieces it is finishing, and the selected media will interact is key to delivering an optimal finish each cycle. Doing so requires understanding why media levels are important, determining and tracking levels, and evaluating media consumption to avoid issues.

How do Media Levels Effect Processing?

Without a proper media level, a machine won’t work properly. Levels that are too high and too low can cause issues that result in poor processing results and unnecessary workpiece and machine damage.

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Using Vibrascope to Measure Amplitude v. Frequency in Vibratory Bowls

When it comes to mass finishing, amplitude and frequency require balance and careful consideration.  Amplitude is a measure of movement and intensity while frequency refers to the rate of repetition.

The wrong amplitude, for example, if  it’s too low, can create a lackluster finishing results and longer processing times. If too high it can cause unnecessary wear and tear on the machine.

Creating Vibratory Energy

Whether rotary or tub style, mass finishing vibrators always include these two key components; a work bowl containing the finishing media and the work pieces. Firmly attached to this work bowl is a vibratory drive system generating the energy to put the mass of media and work pieces in motion. The work bowl with attached vibratory drive system sits on a number of coil springs – in some cases on air cushions – which in turn sit on a machine base. The springs, respectively, air cushions allow the work bowl to “free float” up and down within a certain distance.

vibratory drive
Example of vibratory drive 

The force from the vibratory drive system puts the mass of finishing media and work pieces contained in the work bowl in motion. Depending on the type of finishing machine this force is generated by vibratory motors or electric motors driving a shaft with one or multiple imbalance units attached to it.

Imbalance units are made up of a rotating shaft with out-of-balance counterweights at each end of the shaft. Due to its imbalance, the rotating shaft causes an intensive wobbling effect.

Common drive systems in vibratory bowls and tubs include foot motors for small tub vibrators, flange motors for rotary vibrators, and multiple imbalance units with electric drives for large tub vibrators.

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Preventative Maintenance Enables Mass Finishing Equipment to Go the Extra Mile

Mass finishing machines are workhorses of industrial finishing operations, combining engineering expertise and often a hefty price tag. When preformed according to manufacturer recommendations, preventative maintenance can make a big difference in the length of time between design and decommissioning.

Not convinced? Think of your mass finishing equipment like a vehicle. What would happen if you never checked the air pressure in your tires, changed the oil, or replaced the brake pads? Eventually your vehicle would leave you stranded on the side of the road through no fault of its own.

Mass finishing equipment manufactured by a proven expert such as Rosler is just the same as a vehicle that didn’t get the care it deserved. Without preventative maintenance, your high-dollar investment will break down. However, by performing preventative maintenance according to the manufacturer’s recommendations, your equipment will operate like a well-cared for vehicle, extending the life and return on your initial investment.

Diesel or unleaded fuel, anti-lock or drum brakes, manual transmission or automatic, preventative maintenance varies by vehicle type. Here are considerations for preventative maintenance based on your specific mass finishing equipment type.

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Specifying Polyurethane Qualities Produces Mass Finishing Success

Polyurethane (PU) is an elastomer mix (urethane) material that can be formed into in a wide variety of shapes, sizes, and hardnesses. Its uses range from insulation and cushioning to adhesives and car parts and more. PU’s unique ability to withstand tension and compression while maintaining its shape and flexibility makes it a great lining for mass finishing equipment.

The ability to specify the size, shape, and hardness of PU allows equipment manufacturers like Rosler Metal Finishing to build machinery with custom inserts and linings to protect components and enable precise surface finishing as well as relining existing equipment with upgraded lining.

Our expert engineers create a custom blend of shore hardness, PU type, and forming method to produce durable and resilient materials that can withstand the harsh demands and stresses found within mass finishing operations.

Measuring Material Hardness

The shore hardness of PU is measured by the material’s resistance to localized deformation. This hardness or durometer is identified with a durometer tester, which forces a conical shaped indicator into the surface of the material and then measures the depth of the indentation. The scale ranges from 0-100 durometer with many different properties in between.

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