Many beginners want to quickly understand medical injection molding. As an industry leader, we have involved medical injection molding product engineers and wrote this latest ultimate guide in 2022, which can guide everyone to quickly understand medical injection molding products.
Plastic has revolutionized the medical industry, from disposable syringes and needles to dental implants, orthopedic appliances, and medical devices. Plastic use in the medical field can not only reduce the spread of infections, but also be cost-effective. Injection molding medical plastic products, they can offer a variety of benefits in precision, economy, lightness and durability.
Injection Molding is a process that uses injection molding machines to create plastic products. Injection molding also is a very suitable process for the manufacture of medical devices products. It is widely used, high efficiency, fast production speed, mass production, and provides a wide range of plastic material selection. This wide selection of injection molding materials is critical for medical device products that require a unique appearance and diverse physical characteristics.
Injection molding is the most common process of producing medical device plastic products. In this process, the plastic material is heated and injected into a mold cavities, which forms the shape of plastic part.
The advantages of using injection molding as a manufacturing method include:
● The cost is relatively low. In addition to the early mold input, the more the number of later production, the less the mold cost will be shared, and the final product will be more competitive.
● You can make complex designs with ease because there are no limitations on what kind of part you want to make. In addition to its flexibility, injection molding can produce complex shapes with little effort.
Injection molding is a high-volume production method, which means that it's ideal for producing large quantities of plastic parts.
When you consider that your medical products are subject to medical regulations, the first things that come to mind are ISO 10993, USP Class VI, and FDA regulations. In Class III medical products, your product needs to be ISO 10993 compliant and also supported by USP Class VI and FDA regulations.
● ISO 10993
ISO 10993 is an international standard for the medical industry that divides medical devices into three categories: surface, implant, and external communication. These categories are further divided into three subcategories based on exposure duration: limited, long-term, and permanent. Before you choose a medical injection molding material, it is important to determine which category and subcategory your application falls into. Otherwise, you will not know which test protocol applies.
● USP VI
The United States Pharmacopoeia Convention (USP) is a non-profit organization that evaluates products used in the manufacturing and packaging of pharmaceutical products. USP Class VI refers to a set of United States Pharmacopeia (USP) biocompatibility testing requirements whose standards inform the decision making of the United States Food and Drug Administration (FDA). Specifically, USP has published test instructions for plastics, polymers, and elastomers used in medical devices and surgical devices. In the USP category, Class VI materials meet the most stringent test requirements.
USP Plastics Class VI, which covers materials that pass systemic toxicity tests, intradermal tests, and implantation tests. These tests are directly related to the intended end use of the item and take into account conditions such as patient exposure time and temperature. USP is specific to the basic requirements of pharmaceutical products and their manufacturing technologies. For medical products, however, the USP only serves to provide supporting claims.
● FDA compliance
Food and Drug Administration (FDA) compliance is also often used in the field of medical devices to provide important support in the assessment of user needs. The FDA routinely assesses the suitability of materials for direct and indirect contact with foods. The raw materials, additives, and properties of plastics are specified by the FDA in Federal Regulation CFR 21. Materials that meet the relevant requirements are considered to meet FDA standards. However, this is not a binding requirement for the use of materials in the medical or pharmaceutical fields.
● Biocompatible
Both ISO 10993 and USP Class VI for plastics define testing requirements for biocompatibility, that is, the ability of a material to perform a desired function without adverse effects on the human body. Biocompatibility testing ensures that rubber is safe for use in living tissue by ensuring that the material is non-toxic and does not cause immune rejection. But that's not the case. This is partly because no single test can describe all the information about the biocompatibility of elastomers.
● Medical devices Sterilization methods
Medical devices can be sterilized in a variety of ways. Common sterilization methods include the use of steam, dry heat, radiation, ethylene oxide gas, vaporized hydrogen peroxide, and other sterilization methods (e.g., chlorine dioxide gas, vaporized peracetic acid, and nitrogen dioxide).
1) Gamma irradiation is a sterilization method of ionizing radiation, which involves exposing the materials used for sterilization to gamma rays to achieve the purpose of eliminating viruses and bacteria. Cobalt-60 is the most common gamma radiation source used to sterilize industrial ionizing radiation. The sterilized radiation dose was measured in gray (Gy) or RAD (radiation absorbed dose) units.
2) Steam sterilization, involves the generation or injection of saturated steam in a temperature range of 121 to 148 °C (250 to 300 °F) and a pressure chamber of 15 PSI, lasts long enough to provide sterilization. Some plastic products can be degraded by autoclaving.
3) Ethylene oxide sterilization is an important sterilization method widely used by manufacturers to ensure the safety of medical devices. Ethylene oxide gas (EtO) is often used to sterilize materials that are too sensitive to thermal or radiation sterilization. Many plastics fall into this category, and EtO sterilization is often used in disposable medical devices made of plastic (like syringes, infusion catheters, PVC surgical gloves, etc.). Strict handling requirements and technically complex sterilization process make EtO mainly suitable for high volume sterilization.
Injection molding is the most common process used to produce plastic part components, and it's also one of the most cost-effective ways to produce volumes of plastic part components needed in the medical industry. Injection molding allow mass produce plastic products once the mold has been made. This means that you can produce large quantities of products at a low cost and with high quality, which makes it a great choice for long-term projects or large orders. Injection molding offers a number of advantages over traditional manufacturing. Here are just a few:
1) Cost savingsy
The process is more cost-effective than other methods, such as machining or casting. This is due to the fact that it uses less material and equipment, which means lower production costs for your product.
2) Lightweight
Lightweight parts can be created using injection molding, which makes them ideal for medical device products that require weight reduction but also need structural integrity and durability—like pacemakers and implantable defibrillators (AEDs).
3) Short lead times
This is another benefit of this method because you don't have to wait months before you get your finished product back from the factory after they've already been produced. For some simple products, it may only take a few days to complete.
4) Ease of compliance with FDA rules
FDA regulations are a top consideration for all makers of medical devices. Injection molding improves sterilisation, strength, durability, and handling. Injection moldings controlled nature aids compliance with ISO and FDA regulatory standards.
5) Safety
Medical equipment must be designed to limit the risk of unsatisfactory performance.
6) Design versatility
You can according to the need, design into you need a variety of shapes, structures of the medical device products. Because injection molding can produce most common structures (such as holes, ribs, etc.) plastic parts, which provides designers with a wide range of design space.
7) Durability
Injection molding plastic part has a wide range of tensile strength, durability, and flexibility, making it difficult to mill many softer plastics. Due to the high pressure at which they are formed, the molecules of plastic are compelled to pack closely, improving their endurance. You may always obtain a plastic medical component that meets your needs.
8) Contaminant resistance
A large part of the plastic acid, alkali corrosion resistance, in the process of use, can reduce the possibility of contamination, reduce the risk in use. plastics are easy to resist invading contaminants, and they don't need much disinfection to stay sterile. Because of this factor, medical devices products made of plastic can easily meet the requirements of FDA and ISO 13485 standards and other regulations.
9) Material selection Flexibility
Up to 25,000 kinds of injection molding materials, you can choose any material without any concern, which provides designers with a wide space for design, for the design of innovative medical device products to provide a broad platform.
10) Ergonomics
Many handles of medical instruments and equipment need to be anti-slip and shockproof. Most of these components are purchased to cover molding, so as to meet the purpose of ergonomics. This reduces weight, saves costs, and improves the user experience.
11) Lower upfront investment cost
Injection molding is an excellent method for making plastic parts because it requires less investment in tooling compared with other manufacturing methods such as die casting or injection molding with liquid resin.
Injection molding is the most common way to manufacture medical plastic parts or components. Injection molding uses injection heat or pressure molten plastic to an mold cavities, which then solidifies into a finished product, create a permanent plastic part. The process can be used for many medical applications including dentistry, medical equipment housings, pharmaceuticals, medical implants, lab supplies, surgical instruments, coronary stents, pacemakers, magnetic resonance imaging (MRI) machines, X-ray machines, artificial limbs, artificial hips and knees, etc.
1) Medical equipment Housings
Injection molding are frequently used for medical device housings due to their ability to create distinctive, modern-looking products. They are also strong, lightweight and durable, making plastic shells an indispensable part of many medical devices. And it doesn't interfere with electromagnetic energy, such as CAT scans, MRI scans and X-rays. Some plastic resins are also protected from radiation.
2) Dental products
The development of new high-quality composite materials for injection molding techniques gives dentists another option for quick and simple restorations that achieve ceramic-like results.
3) Pharmaceutical
Common bottle caps, Pregnancy test shell, such as many pharmaceutical industry are made of injection molding. The fundamental reason why plastic can replace glass in the pharmaceutical industry is that it is light, environmentally friendly and cheap.
4) Laboratory equipment and supplies
Plastic components are commonly found in syringes and automatic medication dispensing devices, including those used for insulin delivery and pain treatment. Common laboratory device including non-glass test tubes, petri dishes, beakers, and syringes etc. are manufactured with injection molding. These plastic medical devices are much more durable and lighter than traditional glass materials.
5) Implantable medical devices
In general, medical implants are made from medical-grade titanium. However, with the development of high temperature plastic and the maturity of production technology, many metal implants are replaced by high temperature plastic. In these implants, plastic is used more and more frequently. Weight, cost and performance are the main reasons for replacing metal. The materials of medical implants need to be biocompatible, and PEEK is one of the good candidates. Many implants are made of high temperature injection molding. Common medical implantable include:
● Cochlear implants
● Intraocular lenses
● Pacemakers
● Intrauterine contraceptive devices
● Knee implants
● Hip implants
● Spinal implants
6) Disposables
Surgical consumables are the most often used single-use items in hospitals. For example, syringes, needles, COVID-19 test kit shells and other disposable medical products are inseparable from injection molding process. As the use of plastics in healthcare continues to rise, a growing number of companies manufacture surgical disposables.
7) Orthopaedics
Orthopaedic devices are frequently intended to move bones, ligaments, tendons, and other tissues. Many orthopedic devices are made of plastic because they are light in weight, reduce the burden on patients, and are cheap in price.
8) Device Grip
A soft or textured grip may be a key component of a medical device, such as a handle on a medical or surgical instrument. Adding these friendly soft grips can increase friction and ease of use, and these small details are also very important for medical devices. These grips are usually overmolding. The right choice of resin provides compatible and seamless connectivity for all components of your medical device.
5. Common plastic material for medical devices
Injection molding plastics parts or components are used for a wide variety of medical applications, from disposable surgical instruments to assisted breathing devices. They can be manufactured with a wide range of materials and colors, including polypropylene, polyethylene (PE), polystyrene (PS), polycarbonate (PC), ABS and nylon.
Thermoplastic materials like polycarbonate, polypropylene, polyethylene, and special high temperature polymer blends for certain medical device uses are often used to make medical plastic items.
1) PP(Polypropylene)
It is a cheap plastic that is used in medical applications where medical devices need to be sterilised with steam. In addition to being resistant to sterilisation by steam, polypropylene is also durable in terms of the number of times it can be used. Also, the fact that it can be recycled makes it a good choice for a medical plastic.
2) PE( polyethylene)
It is a thermoplastic that can be used in many ways and lasts for a long time. It is the plastic of choice for medical uses because it is strong, doesn't react badly with chemicals, and doesn't soak up much water. It won't fade, hold harmful microorganisms, or break when cleaned with harsh chemicals. It is often used in medical implants because it is a porous, synthetic polymer that does not break down in the body and is not affected by living organisms.
3) PC(Polycarbonate)
This material is used in a wide range of materials, but it is best known for its resistance to high temperatures and hard hits. Polycarbonate polymers can be used to make lenses for eyeglasses, parts for cars, safety equipment, and medical devices. Polycarbonates are very flexible and can be shaped at room temperature without cracking or breaking. This is because they can handle heat very well. The things about polycarbonate that make it so useful for making prototypes of medical devices.
4) ABS (Acrylonitrile Butadiene Styrene)
Acrylonitrile butadiene styrene is a copolymer of acrylonitrile, butadiene and styrene. ABS is an opaque thermoplastic and amorphous polymer. Acrylonitrile in ABS provides chemical and thermal stability, while butadiene adds toughness and strength, Styrene gives the finished polymer a nice, shiny finish. ABS has a low melting point, which makes it easy to use in injection molding processes. It also has high tensile strength and is very resistant to physical effects and chemical corrosion, which allows plastic products to withstand heavy use and adverse environmental conditions. The heat resistance of this thermoplastic polymer makes it a good metal replacement for structural parts.
5) PEEK Polyether ether ketone
PEEK(Polyether ether ketone) is a high performance medical grade plastic resin with excellent chemical resistance, excellent mechanical strength and dimensional stability, hydrolysis resistance, cracking and fatigue, and can be sterilized by autoclaving. It is FDA approved for food exposure and UL 94 V-0 flammability rating. PEEK has the ability to maintain stiffness at high temperatures and can be used continuously in environments up to 170 degrees Celsius. This engineered plastic has a wide range of applications in challenging environments such as aerospace, oil and gas, medical implants, and semiconductors.
6) PEI(Polyetherimide)
PEI material is an amorphous thermoplastic high performance polymer with high mechanical strength, rigidity, excellent dimensional stability and a wide range of chemical resistance that is valuable in medical, electronics, and other fields where special strength and stiffness are required in high temperature applications. Unfilled PEI thermoplastics are translucent and amber in colour and have exceptional mechanical, thermal and electrical properties. It has one of the highest dielectric strengths among thermoplastic materials. PEI is ideal for hot air and water environments. Many medical implants are made from this material.
7) PSU(polysulfone)
PSU is a semi-transparent, amber-colored plastic polymer that can withstand high temperatures and has good mechanical properties. In addition to continuous operation at high temperatures, the properties of the material include excellent creep strength over a wide range of temperatures, excellent dimensional stability, good resistance to hydrolysis and chemical compatibility. Polysulfone can't be broken down by hot water or steam, so it's often used in places where repeated sterilisation is needed, like the food and medical industries.
8) Silicone
Silicone is a special class of high-performance materials, including reactive silanes, silicone fluids and silicone polymers, that are widely used in a variety of consumer and industrial products: including healthcare, aerospace, personal care, electronics, appliances and more. Silicones offer many benefits to the products that use them, including increased flexibility and resistance to humidity, heat, cold and ultraviolet radiation.
9) TPE
Thermoplastic elastomers (TPEs), a class of physical mixtures of copolymers or polymers (usually plastics and rubber), are composed of materials with thermoplastic and elastomer properties. TPEs combines the processing advantages of thermoplastics with the properties of elastomers. Therefore, they are relatively easy to process using thermoplastic methods, such as extrusion and injection molding. TPEs are the main replacement for traditional medical materials like latex and PVC. Types are susceptible to autoclaving, ethylene oxide, and gamma radiation sterilisation. TPES that are affordable and give a lot of freedom in design and production. TPE has a good rubber-like feel and is often used in personal care, medical and healthcare applications. TPE is also particularly suitable for ovmolding applications.
Choosing the right resins for your medical devices is a key design, functionality, manufacturability, and profitability to achieve the best results. Proper plastic selection is critical for medical devices, as materials need to comply with numerous regulatory agencies and challenging physical properties. Some of these properties include extreme temperature, stiffness, tensile strength, impact strength, and chemical resistance. Chemical resistance is particularly important because very harsh disinfectants can cause stress cracking or dissolution of plastics.
Some medical devices must also withstand prolonged exposure to high temperatures, sometimes during sterilization. Medical devices also need to withstand high temperatures and pressures to maintain structural integrity and have high impact strength. It is difficult to find plastics that exhibit high scores on all of these properties because the high temperature resistance and stiffness of most plastics are usually inversely proportional to impact strength. Plastics used in medical devices must also remain high performance for long periods of time and undergo extensive testing (such as meet FDA test) to verify that they can operate reliably for longer periods of time. How to choose the best plastic resin material for your medical products. Let us go to understand and learn the basis we use to select materials for your medical device products:
1) Strength and impact
The range of medical equipment is very wide, from farenheit thermometer to all kinds of complex machines that hospitals check. Your any new product needs to be able to withstand the kinds of situations it might plan to encounter. If it is a handheld medical device, this may mean that it needs to have the strength, durability, to withstand a drop from a height of 1 meter onto a hard surface without damage.
If your device is used on a stand, it may also need to have the ability to handle impact, or wear resistance if used in travel. Be sure to determine the strength and durability requirements of your product and choose a suitable resin, which will pave the way for the success of your product when it comes to market.
2) Temperature resistance
If the medical equipment must be autoclaved (or steam sterilized), it may compromise the dimensional stability of parts or cause warping or part failure. Therefore, the selection of high temperature resistance, moisture resistance of the village fat is the most sensible choice.
Common high temperature and moisture resistant resins include polyphenylsulfone (PPSU or PPSF) and polyether ether ketone (PEEK). Medical devices made of these materials can often be autoclaved thousands of times without compromising their function and operation.
3) Sterilization
Sterilization is an important part of the manufacturing process for many medical component manufacturers. Choose the most suitable material for chemical and heat resistance according to the end use. Most medical-grade plastics are sterilizable. At the same time, the appropriate low cost is also an important consideration.
4) Chemical resistance
Many medical device products are often exposed to chemicals, so chemical resistance is a link that must be considered when selecting materials for medical products. it is important to choose resins for exceptional toughness and resistance to discoloration and chemistry. Firm the resin to a variety of chemical bactericidal treatments, including polyphenylsulfoxide (PPSU or polyether ether ketone (PEEK), polyether imide (PEI), etc.
5) Biocompatibility
The materials of medical devices that will come into contact with body fluids or tissues must be biocompatible. If the resin is not biocompatible, polymer degradation can occur when the plastic is exposed to biochemical agents and interfering factors present in the human body, and material degradation can have a variety of side effects.
6) Operating environment
The environment to which the medical device is exposed must be considered in the plastic material selection process. Many medical devices are used in harsh environments that require continuous disinfection and sterilization with chemicals. Understanding the context in which your new medical devices are used will help narrow the focus on resin selection.
Other factors such as ambient heat, cold and extreme humidity, chemicals, body fluids, radiation, electrical discharge and conductivity, and other forms of sterilization may also need to be considered when selecting a resin. Make sure the medical grade plastic you choose can handle the conditions where it will be used.
7) FDA Requirements
A major factor to consider in the plastic material selection process is whether the medical device will be implanted and/or come into direct contact with a person. If it will be implanted and/or in direct contact with humans, you must be sure to use a biocompatible resin that meets fda standards. Medical devices that are implanted must follow different rules than tubes, equipment, and other items that are used on the outside of the body. Look at the FDA rules for your application before you choose a material.
8) Molding method
Overmolding and insert molding are often used to making medical devices, but not all plastics can be used with either process. Before choosing a medical plastic material, you need to know how you plan to use it and what manufacture process making them.
9) Additives using
There are often moving parts in medical equipment, such as gears and sliding caps. These moving parts need to have high wear resistance and lubricity to ensure smooth operation for a long time. Adding lubrication to polymers is a good solution, such as polytetrafluoroethylene (PTFE) is often used to improve the resistance of worn moving parts, improve lubricity, and extend service life.
10) Material Cost
Choosing materials with the right physical properties is a primary consideration for medical applications, but cost is still an important consideration, especially when the same needs can be met at different price points. Choosing cheaper materials will make products more competitive.
7. What capabilities are required to produce injection molding medical devices?
The evaluation of a high-tech injection molding machine for producing crucial parts of medical devices is not constrained by the lack of ISO 13485 certifications or cleanroom capabilities. It talks about all aspects of a possible relationship, like their plastic injection molding capabilities and engineering, design skills etc., as well as their willingness to work with you and learn from you to get the best results.
This makes sure that your items won't break when they're being used. When making important parts for medical devices, finding an injection molding partner who can meet these needs requires an unbiased look at five key areas.
1) Scientific Molding Expertise
Because of the particularity of the medical industry, it is a challenge for the manufacturers of plastic medical device products, which not only needs professional knowledge of materials, but also needs to be perfect in the molding process, so it is essential to have scientific molding professional knowledge.
Professional injection molding manufacturers provide molding solutions while optimizing for different products performance, reducing costs and improving efficiency. Use scientific injection molding to improve mold quality and product quality, and use engineering knowledge to improve production capacity and equipment profitability.
2) Professional and in-depth knowledge of the subject
Injection molding is a complex manufacturing process involving many disciplines, from material selection to mold design, making, to molding production. Knowledge of material science, mold design, machining, and molding technology is essential for successful production of a good product.
A scientific plastic injection manufacturer know how to design molds, modify molds, and come up with a variety of cocoa manufacturing options when needed. Such as modifying sharp angles, draft, changing gates, etc.. professional engineers know how to determine the right resin, injection molding engineers know how to set molding parameters to optimize production process. so these are the cornerstone of successful production of a good plastic medical device.
3) Rich Experience in mold design and molding
Form mold design, mold making to try-out and mass production, each step require professional abilities. Mold design is the first step to make a mold, it needs the support of professional knowledge, including runner design, gate type, location, size, product arrangement, parting line. These are closely related to the successful production of late molds.
The tolerance control of mold processing is also inseparable from the quality of the mold, any small detail control is not good may lead to the failure of product making. Experienced mold production team can avoid these problems with their rich experience, it is the cornerstone of mold design and production, but also the cornerstone of the production of good medical device products.
4) Professional and deep knowledge of material
Medical device manufacturers need a partner who knows a lot about pharmaceutical grade plastics and high-performance resin compounds. This is because critical-use medical devices often need sterile antimicrobial surfaces, high temperature tolerance, and more chemical resistance. such as stiffness, impact, temperature resistance, chemical resistance all play a big role in the success of a part and are important elements.
5) Standard quality management process
Quality is the lifeblood of manufacturing enterprises, and any suggestion that can improve quality should be adopted. A high quality plastic parts comes from rich experience, professional industry knowledge and high quality management team cooperation. For any manufacturer of medical devices, in addition to good hardware, strict management of the quality team is also a sign of the production of high quality medical devices.
6) Process and analysis working together
Getting things right every time without delay doesn't happen automatically; it requires expertise and experience. The end customer and medical products manufacturer should work together to ensure the smooth flow of the final product, both in terms of design problem, and the difficulty in the mould making, production process or confusion, all hope that the two problems in the actual production to maintain good communication, manufacturers also should continuously optimize production method, process innovation.
7) Automation production
Automation will almost certainly help you achieve overall efficiency and quality improvements. In particular, the production of high-demand medical device products needs to be produced in a clean room, and automation is a must.
In relative terms, automated operations are almost always faster than manual operations, take up less space, require no interruptions, and can provide consistency that manual operations can’t. Consistency in production cycles not only improves product quality, but also helps you determine more accurate operating costs and production outputs.
8. Medical device Injection molding considerations
When plastic injection molding is used to manufacture medical devices, there are many aspects to consider. This applies not only to the design phase, when engineers examine material selection but to the manufacturing process itself. During all planning and making sessions. There are many considerations including:
1) Meet the FDA, ISO 13485 requirement
For medical device companies to comply with ISO 13485 standards, they must have a quality management system that demonstrates the ability to provide medical devices and related services in compliance with applicable regulatory requirements and customer approval. Having the ISO13485 certification means the ability to determine the documentation and methods of quality control in the production process.
These control quality procedures include risk management and batch traceability at every step of every process used to manufacture components and finished products. According to the FDA requirement, components and devices are classified into 3 categories, whether Class 1, Class 2, or Class 3, depending on the key risk factors associated with the component or device. Each level requires a different level of oversight and compliance.
2) Avoid contamination in production
There are typically four sources of contamination: machinery, mold, material, and operator. contamination occurs when a foreign substance becomes trapped in the molten plastic during the injection molding process. These contamination substances can be anything from excess moisture to dirt, and paint stains from the inside of your machine to sundries.
Because of the particularity of the medical industry, some medical products need to be produced in a dust-free environment, which has to be considered to be produced in a clean room. For medical products that need to be manufactured in a highly sterile environment (such as disposable syringes, and disposable needles), keeping the manufacturing environment highly clean and sterile is one of the most important aspects of the manufacturing operation.
3) Medical Implantation or Direct Fluid Contact
If you design a new medical product that needs to be implanted in the body, or if it's in constant contact with bodily fluids. This may also mean that it requires antistatic, electrostatic dissipation capabilities or the ability to have EMI/RFI shielding properties to withstand X-ray, CT, and MRI scans without degradation over time.
As for implants, biocompatibility is a factor that must be considered. If you only need to resist direct fluid or tissue contact for a short period of time before you sterilize it or add it to biohazard waste for disposal, you don't have to worry too much about biocompatibility.
4) Meet sterilization requirements
Many medical components have a minimum requirement for sterilization capability. This applies to the cover of the device located in the device, as well as any part that will interact with the body. These materials' components must be resistant to contaminants and capable of sterilization to be safe for use on humans. Such as ISO 14644/15697 as well as FDA regulations like 21 CFR Part 11 or 21 CFR Part 820 (which both state that certain products must have an effective barrier against microorganisms).
This means that when making any type of medical device or implantable device (such as artificial hips), you must use materials that are approved by these agencies—and if they aren't approved then don't use them! It's important because there are many different types available depending on what kind(s) specifically need protecting against contamination.
5) Durability
In the medical industry, materials that are easily broken or damaged are not suitable for use. When fragile materials are used, they can cause inconvenience and become a hazard, so it is much more important to ensure that the materials chosen provide resistance to breakage and breakage.
6) Cost
When you want to design a new product, you will always find that the cost of the product will always affect the design, as well as the choice of resin and mold for injection molding. Driven by cost consciousness, you may find that some of your performance standards may need to be changed, that the strict tolerances you think you must have may need to be relaxed, or that overmolding or insert molding may need to be modified.
A lack of cost awareness is likely to cause your product to end up being cost prohibitive or aborted. Understanding cost awareness to maintain a specific margin allows you and your team to plan ahead in the design process to design and manufacture competitive medical device products.
9. How to make a Injection molding medical device Products?
Injection molding is a series of manufacturing activities that starts with design. Although injection molding is a process for producing plastic products, during development you must start managing this task before you are ready to manufacture, including product design, material selection, mold design, mold manufacturing, injection molding process validation, packaging guidance, etc. Early supplier involvement (ESI) is an important part of the medical device development process. We encourage suppliers to participate early, which eliminates design and production risks in the development process so that they can provide you with high quantity products and services.
● Design stage
1) Injection molding part design
Product design is the first step in making a plastic part, and a product should be carefully designed. Plastic parts design considerations include material selection, shrinkage, wall thickness, avoiding sharp corners, Draft, bosses, warping, surface treatment, assembly, etc. A well-designed product will have few errors in the manufacturing process and will provide more stable performance and bigger expectations of the market.
2) Select the right material
Choosing plastic materials is a complicated process that involves things like how they are used in medicine, how well they work, and how much they cost. You might be able to find the best material by making the selection process easier by eliminating groups of plastics and specific plastics based on your needs.
3) Engineering Analysis and verification(Design for Manufacturability)
Engineering experience is especially important for making medical devices and plastic products. Mold engineer design and make molds based on their experience. They use moldflow analysis software to identify possible design defects and use the results of software analysis to propose targeted solutions. Moldflow analysis can help designers eliminate design defects and improve the quality of the mold. Moldflow analysis can minimize the risk of mold making, and save cost and time to market.
● Mold making stage
Before making the mold, we use Moldflow software to check the design of the mold and simulate the injection molding process. Try to think ahead and stay away from some injection molding mistakes. Mold design, steel order and inspection, chiller and bolt hole fabrication, cavity and core side CNC machining, mold foundation and frame fabrication, electrode fabrication, EDM process, wire cutting, polishing, assembly, assembly, assembly, and testing of the mold are the steps in the mold fabrication process.
To make a mold, you have to go through a number of steps.
1) Check drawing:
The mold must be made based on the 3D data, the type of material, and the product specifications. One mold has two sides, and one of them is the solid side or the solid half. The core side is the half that can be moved. The mold opens and closes depending on how the side of the core moves.
2) The making of mold frame:
You can order a basic mold base, which saves a lot of time when making mold plates and replacement parts. Then, use a CNC machine to cut the frame into A plate and B plate, making sure that the major cavity liners and core sides fit well.
3) Order steel for cavity and core liners:
Use a router to mark where the screw holes and coolant lines are according to mold design standards. Next, you need to drill holes for the cooling lines. Block the ends of the through-holes with short aluminum rods. Then set up a lot of cooling loops.
4) CNC machining:
CNC is mainly used to machining the contour of the mold. CNC machining cost is relatively cheaper than EDM, and it is also the main processing method for making mold.
5) Electrodes CNC Making:
CNC milling process can’t make some complex shapes or sharp corners, but EDM can make, which uses electrodes. A CNC machine is used to mill the copper blocks or graphite into the shapes that the CNC programmer wants. The number of electrodes is based on how complicated the mold cavities. EDM electrodes also can be made in the shape of a gate when you need them.
6) Wire EDM:
According to the requirements of mold making, the mold steel insert on the core liner is cut by wire EDM. Wire EDM also is used to make through holes for the ejector system. For using wire cut machining any inserts or holes, tight tolerance always is the key point. the holes or steel inserts without be too tight or too loose. Too loose will cause a flash during the injection. This is why the wire cutting machine is divided into three categories according to the machining accuracy, which are fast wire cutting (the lowest accuracy), medium speed wire cutting (medium accuracy), and slow speed wire cutting (the best accuracy).
7) Die sinker EDM:
Die sinker EDM is mainly used to process sharp corners, thin ribs, hard steel, etc. which can’t be processed by CNC. During the EDM process, the workpiece is worn away by a pulsed discharge between electrodes and steel inserts in spark oil. The electrodes and steel inserts are infinitely close to each other, but not in contact.
8) Surface treatment:
Ways to polish to get rid of marks left by EDM or CNC machining processes, you can use sandpaper, and ultrasonic tools polish. To make way the surface of the forming is treated the same everywhere. Certainly, you also can make textures, like VDI3400, Mold-tech some standard textures.
9) Fit Mold:
This is the final step of mold making. Making a mold Put a thin layer of red ink on the side of the cavity, and then connect the core board and the cavity board. Knock on the cavity plate with an aluminum or copper rod to make sure that the parting surface touches when the mold is closed. Then, pull them apart. If there is a red color in the core's sealing area (where the core meets the cavity), the core and cavity are a good fit.
● Try-out mold and making samples stage
When the mold is finished, it is always necessary to try it out the mold. This is a key step that not only evaluates the mutual cooperation of the parts in the mold but also verifies the design results and confirms the production process. Of course, making samples is part of the purpose.
There are many considerations in the mold try-out stage: such as the first injection should be a short shot, and the mold with slider or core pulling can be ejected only after the core pulling is completely withdrawn. At the same time, the mold can be closed only after the core pulling is reset. The ejection speed should be slower. Pay attention to these problems in order to avoid mold damage in the mold try-out stage. For a new mold, nobody can evaluate whether the functions of the mold are normal, including the injection system, ejection system and side cores system and so on.
● Productions stage
In the stage of mold try-out, the function of the mold has been preliminarily tested. Whether it involves design defects or functional problems of the mold itself, engineers should check carefully with the original design. When product development moves into production, the above problems should be solved. The most important problem to be solved in the production stage is how to produce high quality products and how to ensure the consistency of product quality. Next, we will discuss matters related to injection molding production.
The injection molding process boils down to 9 simple steps:
1) Material enters the barrel
2) High temperature melts and mixes material
3) Created enough volume for the shot-size material in the barrel
4) Close the mold
5) Injection of the molten plastic into the mold cavity
6) Wait for Molten material to cool and solidify (during this process, steps 1-3 are preparing for the next cycle)
7) Mold opens
8) Part ejects
9) Return to Step 4 for the next production cycle
Injection molding looks very simple, but it is not. Any small detail can lead to a bad product. In actual production, how to produce high quality products and how do ensure that the quality of each batch is consistent? This requires strict control of every step of the production process.
Below is common considerations of injection production:
1) The drying time of raw materials shall be in accordance with the standard operating instructions
2) Color mixing should be uniform, and must avoid contaminants in the raw material, such as bugs and mud, etc.
3) The waste material in the screw of the injection molding machine should be discharged. The standard is that the molten raw material discharged is natural color, and there is no black spot.
4) For products that need to be produced by mold temperature machine, mold temperature control is the key
5) No matter what plastic product, molding parameters are the most critical
6) Pay attention to whether the ejection system is smooth
7) As far as possible, use the servo robot and automatic tools to remove the products.
8) Standard quality management system
9) Always pay attention to the problems of the machine itself, such as clamping force, whether the nozzle leaks molten plastic, etc.
10. Common type of injection molding used to medical devices manufacture
1) Gas assisted Injection Molding
The concept of the gas assisted injection molding process is very similar to the conventional injection molding process. In gas assisted molding, the plastic material is injected into the mold cavities as a normal injection process. The molten plastic in contact with the walls of the mold begins to solidify, then nitrogen gas is injected into the mold through well-designed and placed gas inlets that provide the pressure that forces the plastic into the ends of the mold. The path of the bubble is guided by the path of least resistance through the hottest, least viscous plastic, which keeps it centered away from the cooler walls of the mold.
Gas assisted injection molding is often used to produce the traditional injection molding process can‘t produce thick section plastic parts and hollow plastic parts are specially used to solve the defect of shrinkage and warping caused by the thick wall being too thick. It is used to solve this problem by passing gas (usually nitrogen) by creating channels built into the mold.
Gas assisted injection molding process is not suitable for manufacturing plastic products with sharp corners, sharp corners will let the gas pressure drop, and smaller gas pressure unable to push the plastic discharge mold, resulting in the plastic parts' thick section is still solid, can't make plastic hollow to solve the purpose of shrinkage warp.
Advantages:
This process creates hollow parts that are cheaper than traditionally injection molded equivalents. Molded parts as well as cool faster in this process. There is also usually less shrinkage because the thicker parts of the wall are hollow.
The advantages of the process are:
● Stronger parts
● Low clamping force
● Light products
● Reduced warpage
● Minimal residual stresses
● No sink marks
● Greener
Disadvantages:
This molding technique is very difficult to apply to multi-cavity molds, especially if the sizes of the cavities are different. Transparent plastic materials are not a suitable choice for this process, as the cosmetic appearance may deteriorate.
2) Thin Wall Injection Molding
Thin wall injection molding is a specialized form of injection molding that allows manufacturers to create thinner and lighter parts without sacrificing structural integrity. This process can save material, increase productivity, and achieve lower costs per part.
However, thin wall injection molding presents several problems.
● Because of the thin wall, you need higher pressure and higher press speeds to fill all the thin cavities with molten material, prevent freezing, and make sure the part can be stripped.
● Due to the high temperature and high pressure of injection molding, the mold should be unusually hard, and the mold steel must be heat treated, the cost will be higher.
● The raw material must be is high flowability, such as Nylon, LCP, pp, etc.
Thin wall molding is one of the most common plastic injection molding processes in the medical device industry. It is often used to make implants, microsurgical tools, endoscopes and other medical devices.
3) High Temperature Injection Molding
Excellent dimensional and physical stability and elasticity are achieved using high temperature injection molding with high temperature plastic resins such as PEEK, PPA, PEI, PAI, and PPS. They are resistant to corrosive chemicals and water, conduct electricity well, and are relatively unaffected by fire and smoke.
Due to the good biocompatibility and stability of some high-temperature materials, high-temperature molding is widely used in the medical industry. Especially in the fields of orthopedic implants, dental implants, and minimally invasive surgical instruments.
Injection molding with high temperature plastics is extremely challenging because it requires the design of strong molds that can withstand high heat, modified injection molding machines, high temperature resistant mold temperature machines, and special process parameters.
Temperature control is the key to high temperature molding, which needs to control the temperature of the barrel, nozzle and mold.
● Barrel temperature
The temperature of the barrel and nozzle mainly affects the plasticization and flowability of plastics. Each plastic viscosity is not the same, even if the same kind of plastic, due to the source or grade being different, the viscosity will be different. This is due to the difference in the average molecular weight and molecular weight distribution in different types of plastics. For high temperature plastics, the molding temperature is usually higher than 300℃, and the specific molding temperature needs to be determined according to the material and the specific product.
● Mold temperature
The mold temperature mainly affects the flow and cooling of molten plastic in the mold cavities, and it has a heavy effect on the product of performance and apparent quality. The temperature of the mold depends on the crystallinity of the plastic, the size and structure of the product, performance requirements, and other process conditions (melt temperature, injection speed and pressure, molding cycle, etc.).
4) Micro injection molding
Micro molding is a tight tolerance molding process used to make very small plastic parts, typically weighing much less than 1 gram and measuring in millimeters. Many industries benefit from these micro products, including the medical field. Microplastic molding parts are commonly used in surgical devices, implantable devices, wearables, hearing AIDS and other applications. Micro molding processes are also popular in electronics and other industries.
As healthcare providers and patients have pushed for minimally invasive surgery in recent years, medical devices have become smaller and more complex to meet these needs.
Most conventional plastic materials support micro molding, but some key components often use engineered polymers to reduce dimensional stability because of shrinkage. For example, PEEK, PEI, PPSU, LCP, nylon and other materials are common micro molding materials. PEEK, PEI, PPS, PBI, PFA and other high temperature materials are used more in the medical field. In the electronic field, LCP, ABS, and NYLON are used more.
5) Metal Injection Molding (MIM)
Metal injection molding is a process of making solid metal parts with injection molding technology. It is also known as powder injection molding (PIM). The non-negligible reason for the use of metal injection molding in the manufacture of medical devices is that it provides metal parts with excellent mechanical properties, is almost completely dense, and allows easy execution of secondary operations such as plating, heat treatment, and machining.
Metal parts produced by the MIM process are widely used in many industries, such as automotive, electronics, medical, aerospace, sporting goods, optical equipment, consumer goods and weapons, mobile phones, power tools, etc.
In metal injection molding, fine powder metal is mixed with a plastic binder to produce a material suitable for injection molding. The powdered metal and binder mixture is melted, shaped and solidified in a standard injection molding machine. The molded parts are then subjected to an adhesive removal and sintering process to remove the plastic adhesive and increase the density or compactness of the metal parts. These post-molding processes are necessary, they can ensure the metal parts of the correct geometry, composition, and physical characteristics of the metal parts.
6) Silicone Injection Molding
Liquid silicone rubber (LSR) injection molding is a process for producing flexible and durable parts. In this process, several components are needed: syringes, metering units, supply rollers, mixers, nozzles and mold clamps, etc.
Liquid Silicone rubber's heat, chemical and electrical resistance allow it to be widely used in many industries, including component seals, O-rings, valves, medical devices, electronic components, etc. Medical products made of liquid silicone rubber can maintain good stability under sterilization conditions and excellent biocompatibility with skin contact, which makes it very popular in the medical industry.
The design of the silicone rubber injection molding process is similar to traditional injection molding. However, the LSR has high shrinkage, and the material is easy to occur flashes during molding. Designers can through tight tolerances and incorporating additional features in the mold design stage reduce these issues.
Compared with the traditional injection molding process, the Ejector system and high temperature high pressure are normally not used, during LSR injection molding. This gives the part designer more freedom.
7) Overmolding
One of the most widely used applications of overmolding in medical devices is handles, like handles for surgical instruments, Endoscopic medical device handles, etc.
With overmolding, design engineers are not limited to just one material. Rigid thermoplastic parts (we call it plastic substrate) can be molded with a soft thermoplastic elastomer (TPE) handles a popular combination that makes products mechanically strong but comfortable to hold.
11. Conclusion
Plastic injection molding is an efficient and cost-effective process， which produces medical and pharmaceutical parts with high precision, accuracy, and quality levels. By injection molding, we manufacture large and small plastic products. Medical plastics are often made from polypropylene(PP), polyethylene(PE), ABS, and unique polymer compositions. ISO 13485 and cleanroom capabilities do not limit the evaluation of a sophisticated injection molding machine for medical device components. It covers all aspects of a potential connection, including injection molding machinery and engineering skills, mold making, as well as their enthusiasm to work with you and learn from you. When injection molding is used to produce medical devices, it begins with design and many issues must be considered during material selection, planning, and manufacturing. Early supplier collaboration reduces design and production risks.
If you are looking for medical injection parts manufacturers, contact us to get more injection molding services and a more in-depth professional information guide.
