The staff of GIE Media’s Manufacturing Group sends wishes for good health, happiness, and success in the coming year and always. Happy New Year!
Developing parts and devices for the medical industry is a challenging, high-stakes process where time to market and accuracy are critical to success. Evaluating new product designs and materials; iterating quickly when needed; and selecting suppliers that can rapidly, consistently, and cost-effectively deliver prototypes and low-volume production, are important in attaining success.
What to look for in a manufacturer
The medical product development process is all about successfully speeding through the FDA gates, so a manufacturer that can quickly deliver quality prototype parts is crucial. One that has excess production capacity won’t be swamped by a large, rush order that could add unnecessary time to the process. A manufacturer that has successfully removed inefficiencies should be able to provide prototype parts in a few days, not months.
The manufacturer should be fast enough to allow multiple iterations in a condensed period, and have the scale to allow for multiple iterations at the same time, particularly for injection molding.
Competitively priced injection molding enables cost-effective short runs so product developers have more time to react with shorter lead times.
In addition to quick turnaround, look for a manufacturer that offers fast, automated quoting so you can get parts as soon as possible. Time is certainly saved when you can upload a 3D CAD model and receive an automated quote within a few hours.
Look for manufacturers that give immediate design feedback to improve the manufacturability of the parts when the quote is delivered.
Always use an experienced manufacturer that has a reputation and track record for fast, consistent, quality prototype parts on time. Also, can they execute what you ask every time? Do they have a mechanism to apply lessons learned further down the development stage? Do they have scale to do on-demand orders? Can they closely replicate end production manufacturing methods? Do they have materials used in the medical industry and a basic understanding of medical approval processes? If not, you may be using the wrong manufacturer.
Often called 3D printing, additive manufacturing (AM) is an excellent way to quickly evaluate new product designs without making compromises due to complex part geometries and additional tooling costs. Design changes are relatively easy to make and low cost.
Disadvantages of 3D printing for prototyping are higher part costs; limited color and texture choices; and in certain instances, plastic-like materials will differ from the final production material used in processes such as molding and machining. If the surface finish, texture, color, and coefficient of friction vary from the end material, it is difficult to accurately assess the subtle needs and benefits of these properties.
The largest advantage 3D printing offers is accurate form and fit testing as the build process of additive technology can accurately produce the form and size of the desired part, making it very useful for early evaluation of new medical parts. Typically, a medical device developer will use 3D printing to identify design flaws, make changes, and then make second-generation machined parts or invest in tooling to create injection-molded parts.
Many materials can be 3D printed, however, regardless of the material used, the manufacturer of the finished good is responsible for ensuring parts and materials safety and efficacy in the application and environment in which they will be used.
Implantable parts and devices must meet a higher standard of biocompatibility, and all risks to the patient from the materials used need to be understood.
Stereolithography (SL), one of the more frequently employed additive technologies, is regularly used for producing models, prototypes, patterns, and, on occasion, production parts. The process involves building a part (or even a multi-part device as one) in single, thin layers by curing a photo-reactive resin with a UV laser or similar power source. SL is often used to create prototype parts in clear materials to view the flow of liquids through the parts. Some other processes may result in porosity or surface roughness that could impair any desired watertight properties. To aid this process, it’s important to select materials that resist water absorption and are formulated to be clear. For example, 3D Systems’ Accura ClearVue plastic is designed to produce near colorless parts for a range of applications.
For form and fit evaluation of devices, high-resolution stereolithography has expanded applications for medical devices/parts. Rapid prototyping using SL enables near effortless design iteration for form and fit. In addition to accelerating this process, 3D printing allows product designers to focus on the role the part needs to perform, relying on the part’s strength, or the shape and fit, with minimal reliance on the material’s properties.
Selective laser sintering (SLS) is an additive manufacturing process that uses a CO2 laser to draw onto a hot bed of thermoplastic powder. The laser lightly sinters – fuses – the powder into a solid. After each layer, a roller deposits a fresh layer of powder on top of the bed and the process repeats. SLS uses thermoplastic nylons, so parts are accurate and exhibit excellent toughness, however they have a rough surface and lack fine details. SLS can be used to create tough, durable medical prototypes.
Direct metal laser sintering (DMLS) is another additive manufacturing technique used in medical part and device prototyping. The process uses a laser to sinter powdered metal to form fully dense metal parts such as stainless steel and titanium components common in medical devices.
When selecting a 3D printing part supplier, look for an organization that has the reputation for accuracy, quality, speed, and reliability to ensure good quality parts as fast as possible.
CNC machiningCNC machining starts with a block of material before a tool removes material to create a part. This prototyping method often plays a significant role in the early and end-of-life stages of a product’s life cycle because there is no tooling expense and products can be supplied quickly and relatively inexpensively.
Cable strain reliefs molded from medical-grade liquid silicone rubber (LSR).
Machining enables those developing medical devices to test several different part designs in parallel, which in turn, shrinks their development cycle. This upfront, simultaneous testing of prototypes with the same product strength and density as the final product helps device developers be better prepared for passage through FDA gates.
Because device developers can’t merely pivot if they fail a gate – they need to start over – testing multiple design options at each gate offers a greater chance of success to emerge quickly at the end of the process with the right product.
Machining is also important for testing parts and devices with engineering-grade materials. Machined metals and plastics can give the same in-hand feel and weight as the final product, eliminating false information from doctor testing. For any metal prototyping, CNC machining is usually the best choice for testing the product’s strength and weight.
At the end of a device’s life, when demand begins to dwindle, CNC machining can play a cost-effective role to satisfy a need for only a small run of parts. On-demand production limits unnecessary warehousing space for excessive product and the associated financial risks.
Depending on the complexity of the part, CNC machining can be a cost-effective choice for production volumes less than 200. For more than 200 parts, or if design changes are possible before all testing is complete, creating aluminum tooling for injection molding makes sense versus CNC machining.
Injection molding is a common production method during medical part and device development, and can provide production parts made from plastic, metal, and liquid silicone rubber (LSR) materials as early as possible – an important benefit during the FDA gating process. This process offers repeatable, reliable, and consistent results. For most injection molding manufacturers, low-volume is approximately 10,000 parts.
The disadvantages of injection molding at low volumes are the upfront tool cost spread across a low number of parts and the risk that design changes may be necessary after a tool is made, which can be costly. However, using low-cost aluminum tooling versus expensive steel ($50,000 or more), can reduce the financial risk of the initial tooling investment.
It’s important to understand some common shortcomings of injection-molded parts. Some flash, parting lines, weld lines, knit lines, gate marks, and ejector pin marks typically are present on the final part. Extremely challenging or poorly designed injection-molded parts will likely cause challenges later. Parts designed to the best injection molded standards and practices will provide the largest operating window to produce good parts.
Device developers have many plastic, metal, and liquid silicone rubber materials in various grades available to them during prototyping and low-volume production, and each offers different properties and application.
Due to the sterilization need for medical devices, ensuring a material can withstand autoclave, E-beam, or gamma sterilization is important. Material biocompatibility is also critical in facilitating healthy interaction for devices that encounter patients. PEEK and PEI are two plastic materials with long-term biocompatibility that withstand steam autoclaving while keeping rugged physical properties.
USP Class VI and ISO 10993 tests are designed to assess the biological reactivity of various plastic materials in vivo, and while this testing is not a substitute for biocompatibility testing, it often is used by manufacturers to classify materials. Many plastics suppliers find it helpful to have their resins certified as USP Class VI and ISO 10993, especially if the resin is likely to be used in medical devices.
There are many metals that can be used to prototype parts via CNC machining and 3D printing processes as well as metal injection molding (MIM) for increased volumes. Proto Labs, for example, has more than 30 hard and soft metals that can be machined; a handful of available additive metals such as cobalt chrome, Inconel, and titanium; and stainless steel and nickel steel used for injection molding. Particularly hard, tough, and strong, 17-4 PH stainless steel is useful for medical instruments.
Liquid silicone rubber (LSR) is a regular material found in medical products due to its thermal, chemical, and electrical resistance; biocompatibility; and ability to retain its properties at extreme temperatures during sterilization. LSR molding is a common manufacturing process used to achieve quality LSR parts, which can be manufactured in low volumes in a few weeks.
Overmolding – molding a soft, flexible part on the outside or inside of a hard part – is growing in the medical industry and often is more cost effective than assembling multiple components. The over-molded material, such as an elastomer or a liquid silicone rubber, must be easy to clean and should be considered as one part in the design. A surgical device with a rubber over-molded handle is a good example.
There are advantages to using a clear material in prototyping to view the flow of liquids and gain a greater understanding of how everything works together. Parts may be less cosmetically appealing, but if it’s prototyping purpose is to monitor fluid interaction inside the part, cosmetics can be addressed in future iterations.
A method to track iterations that is repeatable and has a low risk of failure or human error should be developed for example, using different color-coded parts to track iterations. Note that major color changes can create molding issues, such as splays and knit lines that can vary by color.
End-use medical products need to be produced from a medically certified material and manufactured in an appropriate environment, such as a cleanroom for some parts. Due to a longer development cycle, it’s important to select a material that won’t be discontinued during the expected production life of the product, or a manufacturer will need to re-pass gates to prove a new material works. Choose materials that don’t have availability issues that could disrupt manufacturing schedules.
Improving probability of success
“It’s important to get the types of materials that will be used in the final product – and particularly materials that interact with the patient – as soon as possible in the testing phase,” says Paul Jossart, manufacturing manager at Nova-Tech Engineering. “The manufacturer must be able to make the device to meet the design intent so they know the device will perform satisfactorily later.”
The faster a manufacturer can get product prototypes into an engineer’s hands, the faster the device can get to market. Because the physics of materials vary, matching the characteristics of the final product material is important to get valid test results.
“Product design and process need to work together for successful product development,” Jossart says. “Hardly anyone ever gets it right the first time. I don’t know how you’d do it without rapid prototyping. The ability to find a prototyping supplier that can quickly turn low-volume parts is critical to success.”
Failing fast, learning what doesn’t work as soon as possible, then working to iterate quickly, is important to passing the FDA gates without having to go back and re-pass them. The right manufacturer can help you do that, moving your device one step closer to market launch.
“Our generators can save lives starting at the 24th week of pregnancy or at a birth weight of 14oz,” explains Armin Hossinger, managing director. “This is something we’re very proud of.”
CPAP generators deliver oxygen- enriched air via tube, administered with a slight positive pressure, helping the baby breathe on its own – stimulating lung development. The positive pressure is created within the CPAP generator’s plastic housing, and the oxygen is transferred without leakage to the patient’s nasopharyngeal zone via a silicone prong or mask. To burden the baby as little as possible, whr Hossinger Kunststofftechnik connects the product’s individual plastic components using a connector system instead of an adhesive to keep the CPAP generator airtight.
Measuring lab challenges
Christian Bindl, quality management supervisor at whr Hossinger, lists the challenges he faces when measuring components for the CPAP generators: “Wall thickness of just 0.3mm, tolerances of just a few hundredths of a millimeter, freeform components with a complex shape, different product colors.”
Capturing the complex geometry of the freeform components can be time consuming because this step must be performed from different angles. Thin wall thicknesses also make contact measuring difficult, and certain product colors require illumination, which must be appropriately adjusted for optical measurement.
Previously, these requirements made quality inspection difficult, protracted, and sometimes costly with the company’s existing optical measuring machine. Measurements sometimes had to be outsourced, creating added costs and reduced throughput. Additionally, there was no space on the company’s optical measuring machine for inspecting other products.
Three in one
In 2014 Hossinger and Bindl began looking for a new measurement strategy as well as an expansion to their existing optical measuring machine. They wanted to measure more products in-house, faster and more accurately. Their search revealed the Zeiss O-Inspect multisensor measuring machine that combines three measurement principles in one machine – a contact sensor, a camera sensor, and a chromatic white light sensor. The machine promised greater precision and increased efficiency, but its measuring range (400mm x 400mm x 200mm) was too small for the large workpieces they manufacture, so Hossinger and Bindl got in touch with Zeiss to get a machine with the larger measuring range they needed – 500mm x 400mm x 300mm.
Freedom to choose
“Contact, optical, white light sensors: the way these three measuring methods interact is unbeatable because these make us highly efficient,” Bindl says, as he demonstrates the capabilities using one of the half casings for the CPAP generator. These half casings, which will later form the hollow space where the CPAP pressure is generated, are measured at the start and end of production, as well as for random sampling. The goal is zero defects during the final function test of all CPAP generators in the cleanroom.
Random sampling of the half casings on the measuring lab’s multisensor measuring machine consists of three phases. In the first step, the Zeiss O-Inspect performs a contact scan of the workpiece, taking about one minute. During this time, the contact sensor captures the location of the positioning holes for the pins which will connect the two halves after assembly. The position and diameter of the sealant shell, to which the tube adapter for administering oxygen is attached, are also defined using contact measuring. This requires achieving tolerances between 0.01mm and 0.02mm to prevent the component from leaking or fracturing.
In the second step, the machine automatically switches from contact to optical measuring. Within about 1.5 minutes, the camera sensor measures the receiving contour for the tube adapter. The translucent half housing – yellow in this version – is illuminated in blue, accentuating the structure. The measuring machine offers blue or red illumination, depending on the workpiece color, to create various contrast levels. The sensor can image wall structures elevated by 0.02mm or 0.03mm. These are used later to modify the CPAP generator to fit the shape of the particular patient’s nose. Optical measuring with the camera is best-suited for this task because it images geometric elements quickly and flexibly.
The process then moves to the third step where the chromatic white light sensor captures the workpiece topography in 15 sec., a point cloud consisting of 3,000 characteristics that identify the sealing contour of the half casing for the matching part.
Precise, fast measuring
“The multisensor measuring machine affords the metrologist a lot of freedom to decide which sensor to use and for what. If the program is already set up, it is even possible to switch from one method to the other without any fuss,” Bindl says.
Bindl and his colleague use Calypso software to program measuring routines, no matter which of the three sensors they’re using.
Calypso is used with different sensors and different machines, so the two colleagues only needed to use one software, although they also added a Zeiss Contura coordinate measuring machine (CMM). Contact measuring programs for one machine can be used on the other. Data captured by the service provider on the computer tomograph can be exchanged with data from other measuring machines.
“This makes us very flexible when choosing our measuring methods,” Bindl says.
The acquisition of the multisensor measuring machine has paid off for whr Hossinger because of its flexibility, accuracy, and speed. Today, the company outsources fewer measurements and, with the Zeiss O-Inspect, Bindl and his colleague conduct measuring tasks with a high degree of accuracy and repeatability.
According to Bindl, adding a Zeiss O-Inspect has given metrologists room to breathe.
Don’t let the name fool you. Northeast Laser & Electropolish (NLE) in Monroe, Connecticut, competes internationally, wins big with medical original equipment manufacturers (OEMs), and applies machining and other disciplines well beyond its moniker.
The journey started in 1993, when Rich Rosselli and Kurt England, two young engineers manufacturing blood analyzers and centrifuge products at DuPont, realized they shared the entrepreneurial bug. England had overseen DuPont’s transition from product marking using roll engraving or screen printing to the then-new process of laser engraving. He saw an opportunity for a laser-marking firm in Connecticut that could be more responsive to customer needs. The partners bought a laser from General Scanning and took the plunge.
“It was a tough sale,” Rosselli recalls. “Two guys and a laser trying to convince medical companies they should change what they were doing and go with us.”
Luckily, their ability to engrave promotional products and firearms found a receptive market, sustaining them for the first two years.
The right people, services
Success in the promotional products and firearms markets enabled NLE to buy an additional laser and to hire more people, launching them into larger industrial accounts. Among the key hires in the ’90s were Tom Hecht and John Franchi who became co-owners through sweat equity.
Hecht was doing quality control at DuPont and pushed NLE into automatic indexing and handling parts, “capabilities serving us well to this day,” Rosselli says.
Franchi joined as a sales engineer and was instrumental in guiding NLE into new opportunities, broadening NLE’s appeal beyond the immediate geographic area. Medical accounts, in particular, were unwilling to send parts any distance just to get laser marking. Franchi noted that many of these parts were electropolished right before laser marking and passivated immediately afterward. So NLE added those capabilities, expanding its marketability.
“At about the same time we took our now extensive laser knowledge and added laser welding,” Rosselli says. “This meant we could assemble, weld, electropolish, mark, and passivate, all within a few days. We had already established a company with a great focus on customers and rapid turnaround. We were using technology wherever we could to improve efficiency. But now people realized we had a really valuable combination of offerings and unique talents in handling parts.”
The big leagues
Franchi brought an exciting opportunity in 2009: “One of the top 40 medical OEMs was building a single-use, outpatient, multi-component device in Costa Rica. The assembly required eleven welds, and every time a weld failed – which happened with some frequency – they had to throw out the entire lot of 300. Once we applied laser welding, the strength went up by a factor of two to three and the reject rate dropped to basically zero.”
Dave Hornak engineered a process that uses a vision system to automatically target the laser and a motion control system to make all the necessary gyrations to orient the part for the 11 welds. The operator simply loads the next part while the machine is welding.
This doubled their production rate, allowing them to price the job so competitively that they’ve been doing it for more than seven years with rising volumes.
“The customer originally thought that we would develop the process and then they’d take it in-house. But when they saw the six-station line we’d built here and the level of complexity involved, they decided it would be better to leave it with us. We now run lots of 3,000 using a fully validated process,” Franchi says.
Rosselli adds that Franchi, Hornak, and their team built and validated the entire line in three months, meeting the customer’s tight schedule. “In most companies this would have been a six-to-nine-month project.”
NLE has gone from a company that performed a few operations on other people’s components, to becoming a contract manufacturer that builds the entire assembly, solving a variety of customer challenges. This has earned them a place as a direct supplier to six of the top 40 medical OEMS and a Tier II supplier to most of the remainder. The latest step in this journey depended on yet more technology – the Tsugami LaserSwiss.
Investments pay off
While the contract manufacturing business grew, so did the complications and frustrations, especially when using outside suppliers. In one case, NLE delivered a welded assembly to a medical OEM but was dependent on an outside vendor to produce a key component. Producing that component required a chemical cutoff, wire EDM, a turning operation for an E-ring groove, and a centerless grind. NLE didn’t have those capabilities, and even its outside supplier had to send out the grinding work.
“Our customer was on us for quality, delivery, and pricing,” Rosselli remembers. “That’s when we called Mike Tierney of the Morris Group. He told us Tsugami/Rem Sales (a division of the Morris Group, Windsor, Connecticut) had a machine that could load 12ft bars of tubing stock and perform all the machining and laser cutting operations in one setup. All we had to do was weld it afterward.”
That machine is the Tsugami S205 LaserSwiss, which combines 5-axis Swiss machining with a fully integrated laser. This gave NLE the ability to apply up to 32 cutting tools in a variety of front, back, and side orientations with laser cutting at up to 20ips (500mm/sec).
“The Swiss-turn accuracy of the Tsugami met the required tolerances of the surfaces that were being ground, and the laser easily cut the slots and areas that were being EDM’d,” Franchi says. “We can do all the machining and laser cutting operations in the Tsugami, making us so efficient that we were able to sell the entire assembly to our customer for the price we were paying for one of the components. The net result was about a 40% cost reduction to the customer.”
Helping ensure success
“Mike recognized from the beginning that most Tsugami buyers have extensive machining experience and are ready to add another machine that has a laser as an additional tool. He knew that while we might have the laser knowledge, we needed to be brought up to speed on machining,” Rosselli notes.
First, the Tsugami/Rem Sales team helped by producing prototypes on the machine to test cycle times and quality. Based on that data, NLE lined up financing and made the investment. At that point, NLE hadn’t completed the required plant extension (now 31,000ft2 of production space, plus offices), so Morris offered to train Hornak and Eric Olander (a mechanical engineer and NLE’s first Tsugami operator) at their facility.
Rosselli says “Morris even programmed the initial process we’d use and selected the tools. And, any time we had issues, Morris had someone down here the same day or the next day – whatever it took.
Speeding time to market
The first success with the Tsugami immediately brought in more work.
“Our supplier rating went up dramatically and it opened other doors,” Rosselli explains. “And as those doors opened, customers brought us additional work for the Tsugami – so much so that we quickly realized we needed another one.”
Franchi cautions, “Just buying the Tsugami isn’t necessarily going to bring you business. In our case we’re using them for products that get other operations. Some parts come off the Tsugami and get a validated welding process. Others come out and get a very difficult laser marking. The Tsugami is part of our overall business strategy of providing our customers with multiple capabilities so they don’t have to deal with multiple vendors.”
Rosselli says, “Roughly half of what goes through here gets only one process, like only laser marking or only laser welding. While roughly half get two or more.”
On the other hand, lots of the one-operation jobs they get came from customers who hired them to do something else.
Franchi explains, “It’s very difficult to get on some of the OEM vendor lists. But once you’re on it you can bid for other items within your company’s capabilities. And one of the biggest things going on in medical today is time to market. Engineers often design parts that are difficult to manufacture, but a LaserSwiss gives the ability to apply all kinds of cutting technology to a problem.”
More than giving NLE an important aid in adapting to customer requirements and reducing part handling, the LaserSwiss is also just plain fast – 6x faster than standard cutting techniques.
NLE initially bought their second Tsugami for a whole new family of parts.
Franchi says they had looked at other machines that combined Swiss turning and laser cutting, but “there just wasn’t really any comparison. They’ve integrated the laser so well and the support we get from Morris is unbeatable. Their engineer was the first person to get us thinking about this technology. I wish I could tell you there was one deciding factor. But everything was better about the Tsugami.”
Rosselli’s conclusion? “It was a landslide; we made the right decision.”
Nearly all medical devices require cleaning during manufacturing to remove particulate, oils, or inorganic contamination resulting from manufacturing processes. The challenge is finding a cleaning process that can handle complex assemblies, intricate shapes, and delicate parts.
Vapor degreasing had been the cleaning method of choice because solvent-based cleaners were effective and easy to use, consistently achieving the high levels of cleanliness required. This changed about 20 years ago when solvents raised environmental concerns. Device manufacturers were forced to switch to water-based cleaning systems and many vapor degreasers were tossed into dumpsters simply from a lack of cleaning solvents.
Today, many new solvent options are available, and they are highly effective, safe, environmentally friendly, and affordable. In response, medical device manufacturers are once again realizing that vapor degreasing is becoming an effective method for critical cleaning.
Solvent technology advancements are leading to environmentally acceptable cleaning options that greatly minimize bioburden issues. Many manufacturers and engineers are discovering that a properly designed and maintained vapor degreaser can be more environmentally friendly than an aqueous system, offering effective cleaning with a lower cost.
Medical device components are getting smaller, and more capable, more complex, and more precise – increasing the challenges of cleaning them enough to satisfy regulatory requirements. A well-engineered process is easy to validate and will reduce costs associated with medical device sterilization by removing bioburden sources from the manufacturing process.
Many factors can cause bioburden in a manufacturing process, but one of the biggest is cleaning with water. Water is the primary growth medium for bacteria. This is one of the main reasons solvents are becoming the preferred choice for cleaning. They are hostile to pyrogens, which simplifies process control requirements for eliminating bioburden.
A solvent-based cleaning process with submicron filtration can run at high production volumes while significantly reducing bioburden. Other benefits include lower energy consumption, a smaller footprint on the cleanroom floor, and lower up-front-cost than water systems.
Vapor degreasing uses low-boiling synthetic chemistries, usually halogens such as the fluorine found in toothpaste, the chlorine found in bleach, and iodine. Typically, these chemistries have high density, low surface tension, and low viscosity compared to water. These factors contribute to the desired cleanliness achieved by vapor degreasing systems.
Other benefits include:
Fast drying – Solvents are very pure, leaving no moisture or residue on parts after exiting the vapor degreaser
Immiscible with water –Solvents won’t mix, so water floats off the surface
Constant recycling – Cleaning fluids are usable hundreds or thousands of times as the solvent never wears out, eliminating expensive surfactants and saponifiers that are never recycled in aqueous systems
With aqueous systems, relatively complex processes must be established to ensure the cleaning water does not harbor bioburden, requiring water-cleaning machines that can be huge – sometimes 15m or 20m in length. The rinsing and drying processes are also complex because a great deal of energy is needed to heat and then evaporate water. Blowers or heated dryers are often used to reach all crevices, and even then, spotting or corrosion of parts can be a problem.
A general rule in cleaning is that you cannot clean if you cannot wet, as better wetting means better cleaning. The relative ability of a fluid to wet a surface can be measured by a composite, scaleless value – the wetting index. The wetting index combines the relevant chemical characteristics to predict the quality of cleaning. The wetting index of water is 14 while the wetting index of modern, non-flammable solvents is 100 or higher (see Figure 1 above).
Aqueous systems’ molecular characteristics significantly increase process validation and process control costs. Air knives and heating systems are also large users of energy and expensive to operate. These characteristics are inherent to water – no amount of pumping, heating, filtration, and treatment is going to prevent water from becoming a growth medium for bacteria.
Even trace amounts of moisture can allow the growth of bacteria and create related bioburden issues, compromising the ability to properly sterilize the device. The liability risks alone justify the expense of investigating vapor degreasing.
Ins and outs
Vapor degreasers come in many sizes and shapes, from benchtop units to those requiring two trucks to move and a third truck for solvent. Systems usually consist of a top-loading machine composed of two chambers, both filled with the non-flammable solvent. It’s a closed-loop system, has few moving parts, and ensures that the solvent is reliably clean for ongoing cleaning needs. Figure 2 (page 26) highlights the basic design of a traditional vapor degreaser.
Cleaning fluid is heated to a boil in the first chamber or sump, which then generates a vapor cloud that rises to meet two sets of cooling coils condensing the vapor back to liquid state. This liquid is then channeled back to the second (rinse) chamber until it is full, then the fluid flows back into the sump.
A basket containing dirty parts is lowered through the vapors into the boil sump where the primary cleaning occurs. Then the basket is lifted into the rinse sump, which always contains clean, distilled solvent that has been condensed from the vapors, providing a final cleaning to the components. The parts then are slowly removed from the machine and on to the next process. Normal cleaning cycles are 8 to 15 minutes per batch, faster than aqueous cleaning systems. The parts come out clean, dry, and immediately ready for packaging or further processing.
Options to enhance cleaning:
- Ultrasonics to further ensure residue-free, clean parts
- Superheat to reduce solvent losses
- Programmable computer controls for process control, repeatability
- Automatic hoists to free up workers, reduce solvent losses
It would be perfectly understandable to assume aqueous cleaning would be the environmentally preferred method of cleaning. However, aqueous cleaning systems generate a waste-water stream that requires treatment before discharge. Many aqueous detergents contain non-biodegradable ingredients, making discharge to sewer systems or surface waters problematic. Cleaners that are biodegradable when new may become contaminated during use; the systems recycle the water but not the detergents.
In aqueous systems, water always needs to be pre-cleaned to ensure there are no trace materials, minerals, or pre-existing bioburden that would compromise its effectiveness. In contrast, solvents come ready-to-use and require no mixing.
Waste water treatment is energy-intensive, and having a large machine emitting large quantities of warm water into the atmosphere of a plant also burdens a facility’s air conditioning system. The energy required to operate a vapor degreasing system is far lower than that required for an aqueous system.
Today’s solvents are much improved compared to products used 20 years ago. New products must meet strict environmental standards and regulations. Those containing environmentally unfriendly chemicals including HCFC-225, nPB, and TCE have been or are being phased-out and cleaning methods are migrating to newer, better, safer alternatives. The solvents available today are not only gentle on the planet but also deliver consistent and reliable cleaning with low overall costs.
A clean choice
As medical devices are evolving into more compact and complex components, cleaning becomes more difficult. Perfecting and validating a cleaning method that works effectively is vital to ensure patient safety. Vapor degreasers are smaller than aqueous systems but have equivalent throughput, are simpler to use, and less expensive to operate.