8 Things You May Consider When You Design Plastic Parts For Injection Molding

Medical Injection molding

Injection molding is a technology that lends to the production of high-precision complex parts for healthcare and medical solutions, especially when part-to-part integrity is required over high volumes. 

While injection molding is a versatile process largely used in the Healthcare industry, not all medical device designs are suitable for injection molding. 

Before production begins, material, shape and feature choices must be wisely analysed.

Eight basic considerations can easily guide you to design a part suitable for medical injection molding:

    In terms of medical device plastic injection molding, there are hundreds of plastic materials to choose from. The best material for you depends on the desired functionality of your part. The design and complexity of your mold also play a large role in determining which materials are best suited for your particular medical injection molding process.

    Determining the appropriate wall thickness for a part can depend on various factors: whether the part is structural, whether the part could become fragile, and, crucially, what the chosen material will be.

  3. DRAFT
    When designing a part for injection molding, it is beneficial to add a draft to the part’s faces. The draft is when the sides of a part are designed at a slight angle instead of running straight. The draft can produce several advantages, such as making it easier to eject the cooled part from the mold, reduction of the odds of deformation, and other issues.
    However, factors like material, wall thickness, and shrink rate can all affect a part’s optimum draft. For this reason, it is helpful to consult an injection molding expert and Medical Device contract manufacturer when deciding on the angle.

  4. RADII
    In addition to determining the appropriate degree of the draft for a part, engineers should consider introducing radii to their designs in order to eliminate sharp corners.
    Not all parts seem suited to having rounded edges. In fact, some parts demand right angles and sharp corners for their function. However, there are two main reasons why it can be beneficial to have rounded edges on an injection molded part: it’s easier for the injected material to flow through the mold and improvement of part integrity.

    Coring out a part reduces its mass and material usage, and then the related costs. However, when the walls and ribs are properly designed, the part can remain just as strong as a fully solid part.
    Besides saving on material costs and reducing weight, coring out helps to produce better injection molded parts by reducing sink and stresses.

    Simple designs are easier to turn into injection molded parts than complex ones. But in many cases, removing complex features would affect the performance of the finished part in medical device production.
    That means engineers must sometimes turn to more complex designs, which include features like undercuts: elements of a part that, because of their shape and placement, prevent the molded part from being ejected directly from the mold.
    When a design incorporates one or several undercuts, the mold generally needs to be formed of multiple components to enable a side-pull motion. This naturally increases costs, since the mold is of a more complex nature.
    Designers thus have two options: simplify the design to eliminate undercuts or consider how to accommodate the existing design.

    Experienced designers and engineers familiar with injection molding are well aware of the effect surface finish has on draft angles. High gloss smooth surfaces can be ejected from a mold much easier than a rough or textured surface. There are numerous instances during the detailing of production parts where designers must minimize draft angles or specify textures on exterior surfaces. 
    There are instances where the texture may have to bleed off on surfaces where the draft cannot comply with these requirements. It is advisable to discuss these requirements with a molder to ensure that the parts comply with the aesthetic and functional requirements of the design.

    If designing a part for injection molding still seems overly complex, the best thing to do is consult an injection molding specialist.

    Creanova, with over two decades years of experience in Medical Device contract manufacturing and Medical Device contract engineering, having a specialization in injection molding technology, can provide you advice on the manufacturing technology and the materials according to your product requirements and help you to navigate through each development phase with ease.
    We will support you to find the right plastic for your medical devices considering the combination of high flexibility – in a way that it can be molded into the shapes you need for your device-, competitive costs, chemical resistance and improved safety for the patient.

    Creanova has extensive experience in plastics for the Healthcare industry, especially in Medical device plastic injection molding, so we can bring your medical project at any step of development and we can support you with a 360° solution: from design, engineering, prototyping up to contract manufacturing (including tooling, production, and final assembly, certified ISO 13485).

    Contact us to speak with one of our production experts!