The type of characteristics in play here can include the melt flow index of the polymer, the viscosity of the polymer, the molecular weight of the polymer, pellet size, moisture content, and variation in additives compounded into the polymer. This list lengthens as the part becomes more complex. Therefore, the validation report needs to accommodate yet-to-be-seen changes in those variables that are beyond the control of the extruder, and often outside the scope of the raw material certification. Determining how much latitude the report should allow will be different for every part, and the customer’s understanding is necessary in defining the extrusion process limits.


The development of an advanced, custom medical extrusion can be very complicated and can take more than several extrusion runs before acceptable parts are produced. The key to success, outside of the extruder’s expertise, is communication. Effective communication is built on the openness of both parties, good listening, and mutual understanding of the issues. It also requires understanding that in validation, there are still future variables that may impact the production process and need to be accommodated by creating latitude in the process based upon the limited data used in the validation report.

This article was written by Timothy Steele, CEO and Founder of Microspec Corporation, Peterborough, NH. For more information, Click Here " target="_blank" rel="alternate noopener noreferrer">

Medical Design Briefs Magazine

This article first appeared in the September, 2016 issue of Medical Design Briefs Magazine.

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