By PTI Engineered Plastics
Reliable medical devices and equipment are essential for researchers and doctors to accurately diagnose and treat a wide range of diseases. That is why there is such stringent oversight from the FDA to ensure these products meet the necessary requirements and specifications. To ensure compliance with regulators, manufacturers follow installation qualification (IQ), operational qualification (OQ), and performance qualification (PQ) guidelines. IQ/OQ/PQ certifies the necessary equipment is present and the manufacturing process to create devices that consistently perform to the desired specifications. Several key areas with specific criteria are critical to the process, yet they are often overlooked or underestimated.
First and foremost, availability is a key factor when it comes to material selection for a medical device. It is important to choose a material that is widely available in the market in which you are located. If the material is not widely available, you may be forced to change suppliers or the material. If there is a change in either, you will be required to prove the new material is equivalent to your previous one. If you are not able to prove equivalency, you may have to re-validate, adding both time and money to your validation.
Do not make pricing a major factor in material selection. While material cost is a large component of the final cost of the injection-molded component, a 5-cent or 10-cent difference per pound is not substantial when compared to the tens of thousands it can cost to re-validate.
One of the basic principles of good plastic part design is to maintain uniform wall thickness (request PTI’s DFM reference tool). If you are not able to maintain a constant wall thickness, a thick-to-thin wall thickness is preferred for moldability.
The simpler the design is, the higher degree of reliability it will have (if engineered correctly). Try to limit undercuts and any other features that require action in the mold. Some designs need these complexities; however, make sure it is necessary before designing it in. Keeping actions to a minimum lowers the risk for mold maintenance issues and mold damage and keeps custom components out of the mold.
Other key fundamentals include proper rib-to-wall thickness ratios, proper draft for part release, and proper gating locations. Most importantly, use a geometric dimensioning and tolerancing (GD&T) scheme that is realistic and does not require unnecessary and overly controlling criteria. For example, if only 3 critical dimensions are needed to fully define how a part is going to function, do not designate more than that.
An effective and reliable tool to use during your project, especially in the part design phase, is plastic flow simulation software. The results of a simulation show if a design is moldable as well as any issues that could occur during the molding process such as warping, sink, shrinkage, molecular orientation, and glass orientation.
Mold Design and Construction:
While the part design for a medical device dictates the plan for manufacturing, the mold design is what truly shapes the final product. If you do not have a well-planned and executed mold design, it is almost guaranteed that you will face struggles down the road, especially if you end up replacing the mold for any reason. So, take your time with the design and construction.
If you intend to use the mold to manufacture millions of parts, you must make sure you select materials that can withstand 20 years of production versus only short-term requirements. If you fail to use the proper material to build the mold based on resin and project requirements, you may have to replace it prematurely, which may not be beneficial for your overall validation costs in the future.
Proper Protocol Documentation:
Once you have an approved mold design, you and your team must document the design specifications that outline the specific details about the mold and how it should perform. These details are then fed into the installation qualification (IQ) for the mold to ensure it is qualified and performs properly. As soon as the IQ is complete, operational qualification (OQ) and performance qualification (PQ) protocols are generated outlining the entire process.
If you are using automation, details such as what the proper interlocks are and how they perform, what parts are being used from what supplier, and the location where each part goes should be outlined. Even something as specific as steel dimensions could be included in the IQ protocol. That way should the mold become damaged, or components must be rebuilt, the IQ protocol can be used as a reference for the steel geometry needed. Not only does this help save time, but it also helps avoid a re-validation should you have to use a spare component or rebuild the tool.
Careful attention to detail with regard to these key areas will not only reduce the overall cost of validation, but also reduce production downtime and ensure the long-term success of your project.
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