Plastic injection molding is used to make many medical products. This manufacturing process is proven reliable and can produce large quantities at low costs per part. Injection molding allows for design flexibility and manufacturing integrity with no compromises to the part-to-part relationship. However, not all medical equipment and devices are injection-molded. There are medical products that do not contain any plastic.
CNC Machining is an alternative to plastic injection molding. When it comes to selecting materials to machine, polymers may not be the best option. Metals can be used in surgical scalpels. Ceramics are used for bone screws. Silicone elastomers can also be used in wound management and drug delivery. Why would you choose plastic injection molding to design a medical product?
Before moving on, you must understand the advantage and disadvantages of plastic medical injection molding.
What are the benefits of plastic injection molding in medical products?
There are many reasons why medical plastic injection molding is used, but these are the most important.
- Low per-part costs and high volumes
- Complexity of design and manufacturing
- A wide range of medical supplies available
Let’s take a closer look at each one.
High volumes with low per-part costs
Medical injection molding can be a high-volume manufacturing method. Although a steel tool or mold can be costly, it is affordable if you spread the cost across multiple parts. After you have paid for the injection mold, you will have covered a large portion of your project’s costs. While there are still labor and materials costs, this is true for all manufacturing processes.
Plastic injection molding is much faster than CNC machining. An injection molder can produce many parts at once using automated equipment and a multi-cavity mold. The cycle time is measured in seconds. Plastic machining can take longer and may not produce as many parts as you require.
The Complexity of Design and Manufacturing
High levels of Complexity can also be supported by medical injection molding. Plastic injection molding can create features like bosses, ribs, holes, threads, threads, custom colors, textures, and threads. Injection molders can produce medical plastic components that are difficult to make or expensive, regardless of whether they need support structurally or aesthetic appeal.
Even if the component of your plastic medical device is not complex, precision and accuracy are important. Accuracy is how close an item’s measurements are to the true value, while precision is how close they are to one another. Plastic injection molding can provide high levels of accuracy due to tight tolerances. Precision, or part-to-part consistency, can be achieved with high volumes of plastic injection molding.
Wide Selection of Medical Materials
You can choose from a variety of materials for medical injection molding. They come in a range of price points and properties. But it is not the number of options that matters. It’s not the sheer number of options that matters. Instead, it is the ability to choose a material with the required attributes. A disposable applicator, for example, can be made of a cost-effective and impact-resistant commodity plastic.
Some medical products may require a stronger but more expensive engineering plastic, a biocompatible material, or an antimicrobial polymer. Plastics can also withstand repeated sterilization by steam, radiation, or ethylene oxide (EtO). Want.Net’s Manufacturing Partner network offers polymers that can be traced and medical-grade plastics that have FDA approvals.
Plastics are generally lighter than metals and usually less expensive. You can still use metal parts if necessary with insert molding or overmolding. These two plastic injection molding techniques can be combined to create bonded assemblies made from multiple materials. Overmolding is where a soft silicone can mold over a hard plastic part made from a polymer like a polycarbonate.
Although medical plastic injection molding has many advantages, it may not be the best choice for your project. Let’s now look at the cons.
So what are the drawbacks?
Three main areas are the downsides to injection molding:
- High tooling cost
- Design challenges
- Problems with processing
Let’s take a closer look.
High Tooling Prices
Tooling is a must for plastic injection molding. Your return on investment (ROI), if your production volume is too low, could be too high. Due to the importance of quality, medical injection molds are more costly. A few microns can mean the difference between functional and defective plastic parts in medical device manufacturing.
A steel mold with a high-quality finish is required if your medical product needs high precision. Plastic injection molding may be cheaper than additive manufacturing molds. However, 3D-printed molds can only support a limited number of cycles and may not have the required precision and accuracy.
Design Challenges
Your injection mold’s cost is not the only consideration. It is important to properly design the mold and consider variables like parting line geometry and venting. You also need to think about the part’s design. The plastic part must eject smoothly when the two halves are open. If the part is not ejected smoothly, it could cause damage.
If you have already created your part, you might need to make design changes. It is also important to consider the size of your part. Injection molding larger plastic parts could prove costly due to the high cost of tool steels.
Processing issues
There are many issues with medical injection molding. This is due to the way plastics are processed. Even if your mold design is perfect, it may not fill if the temperature and pressure of the molten plastic are incorrect. While skilled injection molders can correct viscosity changes, they need to adjust their equipment constantly. This increases the risk of part quality issues, longer run times, and higher scrap rates.
Plastic injection molding is environmentally friendly, as some waste materials can be recycled. Even runners and sprues can be ground. Certain medical products may require virgin plastics. However, it is better to avoid waste as regrinding increases labor costs and delays project timelines. Due to the part’s thickness, mold shrinkage may also occur. Mold flash might need to be removed during post-processing.
