一, Why do injection molds for medical products need better exhaust systems
In medical devices, bad exhaust often means that the product has to be thrown away right away. In normal plastic products, on the other hand, these problems just include burning, short shooting, or silver lines on the surface. medical device injection casting frequently uses highly accurate and small-scale structures. Everyday medical supplies like catheters, syringes, valve bodies, and medication containers have long flow pathways, thin walls, and complicated cavities. If there isn't enough exhaust, the molten plastic will run into air resistance at the end of the filling process, which can easily cause partial filling or bad welding.
medical injection molding materials are very process window sensitive. PP, PE, PC, ABS, TPU, TPE, and other medical-grade materials often need stable shaping conditions and fast injection speeds. Once the air inside the mold cavity can't be quickly let out, it will be quickly squeezed by the high temperature and pressure,
二,The basic ideas behind the exhaust system design for injection molds for medical devices
There are some basic and strict rules that apply to the whole process of building mold structures that need to be kept in mind when planning the exhaust system for medical device injection molds.
the exhaust has to be "enough but controlled." Exhaust that is too weak or too strong can cause problems like flash or pollution. So, the exhaust groove's depth, width, and position must be carefully controlled to make sure that the air can exit smoothly and that no melted plastic spills over the sides.
the way for the exhaust should be as short and smooth as possible. The cavity of medical injection molds is normally small, and air can get easily caught if the exhaust path is too long or there are areas that you can't see into. A good design should let air be directly released at the end of the filling instead of having to go around complicated parts of the system.
the exhaust system should be simple to keep clean and in good shape. Medical device manufacturing stresses cleanliness, and if dust or breakdown products build up in the mold, they will impact the quality of the product. Because of this, exhaust systems should not be made in ways that are hidden or hard to clean.
三,In medical device injection molds, structure design and common exhaust methods are used.
In practice, the exhaust system of medical device injection molds often uses a number of different structural combinations to make sure it can work with complicated shapes and high precision.Parting surface exhaustion is the most usual method. When you machine small exhaust holes onto the parting surface of the mold, the air in the mold cavity gets squeezed and pushed out at the end of the injection molding filling. This approach is easy to keep up with and has a simple structure. It is the most basic and most commonly used way to remove air from medical injection molds. For medical good
Ejector pin exhaust is often used on medical device parts that have thin walls or long flow distances. There is a small gap between the top pin and the hole for the top pin. This can work as a second route for the exhaust. During design, the ejector pin's position can be fairly spread out to allow the exhaust function at the filling end. This approach doesn't need extra work on the exhaust groove, but it does need to be processed and put together very precisely.
四, Common issues and important facts about the design, medical injection casting exhaust system
Even if the right exhaust method is used, the system can still fail if the details are not carefully managed. So, during the design and validation process, these things must be focused on. make sure you have power over the size of the exhaust duct. Burrs can really mess up medical device molds, and the width of the exhaust groove usually needs to be changed in a very small-scale way based on the properties of the material. The melting point and flowability of different medical-grade plastics are not the same, and the exhaust size can't be based on trial and error.
Second, the reasonableness of the exhaust position. The exhaust needs to be set at the last filling point of the melt instead of being spread out all over the place. Figuring out where air will get trapped by looking at flow patterns is an important part of medical mold design.
Once more, it's the passage's cleanliness and longevity for exhaust. Some materials used in medical injection casting may break down at high temperatures, easily adding carbon to the exhaust duct. Avoid making exhaust structures that are hard to clean and are too deep, too narrow, or difficult to clean during design. add exhaust system checks to the mold maintenance plan.
