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Medical and Healthcare
When it comes to healthcare, there is no room for error. Medical plastic parts are subject to the most stringent quality tests, from the development phase to high volume production. Medical products range from disposable packaging, syringes, petri dishes and test tubes to parts for sensoric and diagnostic equipment and plastic implants. There is a large variety of medical grade plastics, most of which are sensitive and can only be molded within a very specific processing window.
Rheo-Pro® high performance hot runner systems are ideal for the production of medical parts. Hot runners cut production costs dramatically by eliminating cold runners, including related part handling and regrind material. They also complement clean room molding operations because the molding cells produce only parts and zero cold runner waste.
Valve Gating
Valve gate systems improve part quality by delivering extremely clean gate marks. For example, a PP container cap with a metal foil insert and an elastomere over-mold. The over molded elastomere film is a 0.3 mm thick layer that is direct-valve-gated as a secondary shot with a volume equivalent to only one plastic pellet of 10 mg². Applications like this are possible because of the accuracy of advanced valve gate systems that can deliver the repeatability of shot volume (within the milligram tolerance range) and the quality of the gate vestige (± 0.05 mm pin position).
Valve gating reduces cycle time and is often the preferred method for producing medical parts because a valve gate offers more controlled processing conditions than thermal gating or side gating.
Flex PVC oxygen mask for infants, direct valve gated
Thermal Gating
Thermal gating or hot tip gating generally involves a smaller up front mold investment compared to the cost of valve gating but offers a narrower processing window. Hot tip molds are also more sensitive and therefore more challenging to start-up and to operate. The resulting gate vestige often becomes a critical issue for medical parts because the gate is essentially a micro-fracture of up to 1.0mm diameter, directly on the part surface. However, it is a suitable approach for certain applications.
Hot tip gate nozzles can be used in applications where a gate vestige is permissible on the part. Only relatively small parts with shot weights between 1 and 50 grams qualify for hot tip gating. This is certainly a point of specification prior to hot runner selection and design. Materials with a brittle fracture such a PMMA and PS should not be hot tip gated for medical parts whereas ductile polymers such as PC, PP, PE are more suitable, especially when the gate can be sunken into a dimple or depression in the part surface.
Complex micro parts for medical device components produced with Rheo-Pro® thermal gate (hot tip) nozzles
Multi-tip Nozzles
Rheo-Pro® multi-tip nozzles such as the M05 and M05VG are compact and cost efficient. One nozzle with up to six tips can gate a cluster of parts. Pictured below is a part produced in an X-manifold with four 6-drop multi-tip nozzles, representing a very compact 24-cavity mold. This mold operates with PSU (polysulfon) at 380˚C melt temperature and 180˚C mold temperature producing 20 mg medical parts at a 5 second cycle time.
 
A 36-cavity mold for insulin syringe needle protector caps illustrates the compactness of mold design with multi-tip nozzles. This compact mold with 290 x 390 mm (11.5" x 15.5") has the capacity to reproduce 150 million micro parts per year without regrind. The hot runner can run maintenance free for millions of cycles. The gate vestige rests safely in a 0.6 mm deep dimple.
32 cavity hot half featuring Rheo-Pro® multi-tip valve gate nozzles with tight gate spacing and optimized melt residence time for small plastic parts
Careful consideration has to be given to the calculation of the melt residence time inside the barrel and melt channels. This is of particular importance for heat sensitive materials and additives such as color pigments, nucleators, clarifiers, lubricants and stabilizers.
Multi-tip solutions are available with both valve gate and thermal gate nozzles (illustration: front accesible thermal gate tips, nozzle heater, and thermocouple)
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Rheo-Pro® Hot Runner Systems |
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Superior part quality |
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Faster cycle times |
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Ideal for clean room molding cells |
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Optimized for automated, high volume production environments |
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Side Gating
Rheo-Pro® SG side gate hot runners are specifically engineered for high cavitation molds that require side gating into multiple cavities per nozzle. SG hot runners offer an ideal solution for long and tall tubular parts such as syringe barrels and medical applicators.
SG hot runner systems are easy to install. The unique nozzle design reduces the mold cost significantly in comparison to other more cumbersome side gating methods, such as disks, where the cavity inserts must shift towards the nozzle tip, creating an unnecessarily complicated hot runner assembly.
Custom Engineered Tips
Standard nozzle tips are not always able to produce parts with challenging gate locations. Some plastic parts allow only side gating with edge gates or internal gating. MHS offers custom gating solutions and custom gate or nozzle tip designs. Not all hot runner suppliers offer this level of flexibility and customization.
  
High Cavitation
High cavity hot runners are required for production volumes exceeding tens or even hundreds of millions of parts per year. A 32-cavity mold at a cycle time of 6 seconds can produce between 150 million to 200 million parts in a 24/7 operation. Mold down time is not an option in a continuous, fully automated production environment. A mold that produces extremely thin wall, small parts in polycarbonate (PC) at an injection pressure of 2500 bar (35,000 psi) with a part weight of only 70mg, for example, requires a highly reliable hot runner system to achieve consistent results. Medical hot runner systems require absolute repeatability, perfect functionality, and a high degree of flexibility for special and innovative part designs.
Syringe plungers produced with a 128 cavity N04 valve gate hot runner at a cycle time of 8 seconds
Multi Material Molding
MHS offers spezialized hot runner systems for multi-material or multi-component plastic parts including insert mold and overmold technology.
Tamper proof medical closure with metal/paper membrane insert and TPE overmolded skin, direct valve gated
Clean Room Molding
MHS designs and builds medical hot runner systems optimized for clean room operation. Ease of mold maintenance is important in any injection molding environment but even more so in medical part production. All components and processes must be compliant with healthcare standards. Rheo-Pro® hot runner systems offer user friendly features such as fast, easy access to tips, heaters, thermocouples and gates. Valuable production time can be saved by simply sliding the cavity plate onto the core side while the mold still inside the machine. All MHS hot runners feature fully front serviceable nozzles with patented, self clamping heater technology, and easily accessible thermocouples and nozzle tips. New cooling-free valve gate technology further improves uptime by reducing maintenance and improving mold performance.
New Black Box™ pneumatic valve gate actuators are ideal for clean room applications since they operate without lubricants, o-ring seals, or cooling, even with high temperature materials like PEEK
 M3 Injection Molding Machines
Our all new electro-pneumatic injection molding machines offer unparalleled performance in an extremely compact, user friendly package. The M3 series features our patented ISOKOR™ technology, specifically designed to address the unique challenges of molding small, direct gated plastic parts. From prototype, to low volume, to mass production - the M3 series delivers superior part quality, speed, and flexibility.
M3 injection molding machines offer a fast, seamless transition from protoype to high volume production of small to micro-sized plastic parts, using low cost cavity inserts
M3 series molding cells operate using compact and cost effective modular inserts, each containing eight micro cavities, completely doing away with the traditional injection mold structure. It simplifies the mold design and speeds up the transition from prototype molding to mass production since all processing parameters and conditions are identical in both. No additional validation is required.
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