Medical Plastic Processing
Medical Devices as Special Class of Product
A medical device is an instrument, apparatus, implant or similar related article that is used to diagnose, prevent and treat disease or medical conditions by physical, mechanical or thermal means. Medical devices vary in their complexity and application. The category includes disposable items as well as durables, from high mobility to fixture status items. From simple devices such as thermometer, tongue depressors and gloves to advanced devices such as computers which assist in medical testing. In all this diversity of products in this category, there is one thing common to all medical devices, and that is zero tolerance for defects in high precision manufacturing.
Use of Plastics in Making Medical Devices
Given the wide range of medical devices and their applications, plastic is the most suitable material for making them. Wide range of plastic resins are used to make medical devices including: Acrylonitrile Butadiene Styrene (ABS), Polycarbonate (PC), Nylon (PA), Polystyrene (PS, HIPS), Polypropylene (PP), Polyethylene (PE, PET, PDPE, LDPE), etc.
Manufacturing Processes for Making Medical Devices
Prime processes for making a Medical Device using plastic are Blown Film, Extrusion Blow Moulding, Extrusion Profiles, Injection Moulding and Injection Stretch Blow Moulding. Extrusion is a continuous process, enabling production of long length of a product. However, continuous extrusions are often cut in application lengths. Injection Moulding on the other hand is a fast process used to produce large number of identical items.
Challenges in Manufacturing Medical Devices
Nylon, Polycarbonate, ABS and Ploypropylene are hygroscopic in nature and absorb moisture from their surroundings. Polyethylene and Polystyrene do not normally absorb much moisture but are able to carry significant moisture on their surface if not stored in dry environment during the transit to manufacturing facility. Improper drying of resins can cause defects in the product, like low tensile strength and impact resistance, surface cracking, internal cracking, surface lines, bubbles, silver streaking, etc, leading to rejection.
The Injection Moulding process involves injection of plastic melt into the mould and cooling the melt in the mould to take the desired shape. Water Chillers are used for quick cooling of plastic melts and to reduce the cooling time in a particular cycle. However, when chilled water is used for cooling the plastic melts, the moisture present in air in the vicinity of chilled mould surface condenses, leading to formation of water droplets on the mould surface (Mould Sweating).
Mould Sweating is undesirable, as the condensed water droplets tend to drip on the machine bed and seep into the mould, which causes rusting and severely affects the life of expensive mould and machine bed. Further, condensation in the core and cavity of the mould will lead to defects in the moulded component.
Injection Moulding being a fast process and Extrusion being a continuous process, require continuous feed of blended resins into the processing machines. Handling of resins in the shop floor is a complex job, especially since the production area where extrusion machines are placed are lengthy and large. Employing labor to handle resins manually is open to human errors like spillage of resins and delay in changeover of material. Feeding material continuously requires constant monitoring which becomes a tedious task manually, over longer period of time.
Solutions Offered by Bry-Air for Processing Medical Plastics
Drying Parameters : Drying Time • Air Flow • Temperature • Dew Point
While temperature, drying time and air flow are dependent on the type of resin, there is a huge difference in quality of molded component if the dew point can be maintained at minimum –40ºC. Dew point plays a very critical role in creating a lower vapour pressure around the surface of the resin. This lower vapour pressure forces the moisture in the molecular chain to dissipate out to its surface.
Bry-Air Honeycomb Resin Dryers with BryWheel
Bry-Air resin dryer with BryWheel ensures that you have better control over dew point and temperature. The generation next BryWheel Rotor works on Honeycomb Technology, ensuring 25% more energy savings as compared to other technologies available in the market. BryWheel Rotor is specially crafted for a very low dew point (upto - 65°C).
Bry-Air offers options for stand alone, single station as well as multistation centralized installation for your resin drying needs.
Bry-Air Mould Dehumidification System
Bry-Air EcoDry Mould Dehumidication System is designed exclusively to prevent mould sweating.
A chilled water pre-cooling coil combined with latest in desiccant technology ensures super dry air, preventing mould condensation.
Bry-Air Conveying System
Bry-Air Conveying System not only ensures continuous feed of material into machines but also right material for the right machine and at the right time. It further facilitates quick change over of material, making it a one stop shop for all your material conveying needs for shop floor. Bry-Air Auto Loaders automate the transfer of plastic pallets from shipping containers and storage bins to the processing machines.