Designers can successfully design premature failure out of parts and assemblies by giving proper consideration to service conditions, material selection, structural design, residual stresses and molecular orientation, moldability and geometric features, mold design, environmental compatibility, and assembly methods and related stresses.

Automation of Medical Device Molding

There are a variety of elements in the molding process that can be automated:

• Material Handling: Part Removal

• Mold Setting: In-Line Assembly

• Process Data Input: Packing/Boxing

• Quality Control: Production Analysis

The degree to which a project can be automated depends upon:

• Part Design

• Quality Demands

• Run Length

• Economic

Normally, higher levels of quality will justify higher levels of automation.

Clean Room & Fundamentals of Clean Room

Clean room conditions are indispensable for the production of medical moldings. Clean Rooms are sterile spaces in which precisely defined climatic conditions prevail and where a certain concentration of particles and micro-organisms is not exceeded. Injection molding of medical products is normally carried out in clean rooms of class 100,000 or 10,000.This means that a maximum of 100,000 or 10,000 particles, respectively, are admissible per cubic foot. Additionally, a particle size of 1 micrometer must not be exceeded. For comparison purposes, the ambient air of a major town features between 100 * 10^6 particles per cubic foot, i.e. the pollution is a thousand times greater.

Principals for Designing Medical Parts for Plastic Joining

Plastics joining of medical instruments are a continuously growing and developing process for the extensive array of devices used in the medical industry. To successfully take advantage of this technology, Engineers and Designers need to be knowledgeable of the tools at their disposal and how best to utilize them. In order to gain an understanding of the various manufacturing disciplines and which one is best suited for the assembly of the product, it is beneficial to have a basic knowledge of the fundamentals of plastics joining. The processes involve the generation of surface and intermolecular friction at the joining interfaces of the part halves. When the joint interfaces reach their glass transition points, melt and flow develops and joining takes place. The materials to be joined must be in the thermoplastics family have similar molecular structures and melt temperatures.

Medical Plastics failures from Heterogeneous Contamination

In the health-care industry, failure criteria are often considerably more stringent than in other plastics market sectors. This vigilance is necessary because even minor, seemingly innocuous device defects-especially those biological in origin-could have devastating consequences for the patient. As a result, many visual inspections are built into both the manufacturing process and clinical protocols. Failures detected in these inspections are frequently cosmetic in nature and have no impact on the functionality of the medical device or drug container. However, because of the industry's precautionary practices, most of the defects are deemed unacceptable, and the affected products are rejected. The source of these cosmetic defects is often contamination from external sources. Microscopic morphological analysis is an indispensable tool for this effort. Another class of failures that originate from heterogeneous contamination involves inclusion in device components. If the inclusion is of a different modulus from the matrix material, it can act as a stress concentrator and cause premature mechanical failure well below the designed stress of the device. Third classes of failures are due to external sources: those arising from the uneven distribution of additives and modifiers in the polymer. Since many additives are designed to protect the polymer against oxidative degradation, an uneven distribution can result in part of the product being unprotected during long-term aging, which can lead to premature failures.