The procedure for validating the medical injection molding process is critical to verify that the system offers repeatability, assurance of accuracy, and a high degree of quality. It’s important to validate your medical injection molding process so it’s consistent and it’s tracked and traceable. To meet these requirements, manufacturers use a three-step validation process described as:
- Installation Qualification (IQ)
- Operation Qualification (OQ)
- Performance Qualification (PQ).
These procedures help qualify Tooling, Materials, Equipment, Systems and Processes. The goal is to validate that the entire life cycle of the program is repeatable and traceable with a high confidence level that the quality repeats from lot to lot and year to year.
The focus of this article will be on the injection molding process. There are four major variables that control the process: melt temperature, fill speed, pack pressure and cooling rate. Three of the variables are easy to duplicate from run to run. However, measuring melt temperature has always been a mystery, as it is difficult to measure accurately. Molders agree that melt temperature measurement remains one of the “last frontiers” of injection process control.
“You can’t control what you can’t measure” is a fundamental axiom, and the problem here is the lack of an accurate, repeatable, practical, and generally accepted method of measuring the melt temperature.
Why is it important to control melt temperature?
Melt temperature influences the plastic’s viscosity or resistance to flow (thinness or thickness), which is critical in obtaining optimal part dimensional control. Consistent viscosity allows for repeatable filling of mold with consistent cavity pressure, and less part to part and lot to lot variation. You will get a tighter “bell curve” on dimensional variation.
A revolutionary new system has been in development for the last 4 ½ years called the Melt Temperature Measurement System (MTMS). There are two major principles that define the system.
- An insulated cup is used to keep the purge molten so it can be measured before it solidifies.
- There is a defined flow path in the system that forces the molten material over the thermocouple probe.
A high-speed pyrometer records the peak temperature. It is fast, repeatable and easy to use. Gage R&R studies have been successfully completed.
OEM Medical Companies should ask in-house molders and contract molders if they are monitoring and documenting melt temperatures. Contract or custom molders should be monitoring and documenting melt temperature as a Standard Operating Procedure (SOP) to improve your medical injection molding validation process.