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 is 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 the production of a 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 a large number of identical items.

Challenges in Manufacturing Medical Devices

Moisture Problems

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 a dry environment during the transit to the 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.

Mould Sweating

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.