Introduction
Have you ever been to the hospital? Many medical products, such as injections, syringes, IV lines, normal saline bottles, and other plastic products, are used excessively. Guess what? Their accuracy is paramount; otherwise, syringes or IV cannulas are rejected if they don’t meet the standards.
All such products rely heavily on injection molding processes. But the typical question is about— how to design medical injection molds? Today, we will discuss various requirements, processes, and guidelines for injection molding designs. Let’s know!
What is Medical Injection Molding?
Injection Molding is a process for manufacturing various plastic components. In the medical industry, many plastic components require precision. Within injection molding, it is challenging to produce those components unless you have the right design.
Remember, medical injection molding differs from conventional molding processes in several ways. For example, it requires:
- Extremely tight dimensional tolerances
- Excellent surface finish
- Haute répétabilité
- Minimal flash and defects
- Biocompatibility support
- Sterilization compatibility
- Long production life
These molds are made of steel and other solid materials.
Tip #1: Know Key Design Requirements for Medical Injection Molds
Since medical tools are the most critical, even slight errors can get things out of hand. Therefore, you should prepare accurate designs and understand the following requirements.
Requirement #1: Precision Dimensions
Medical equipment is different from traditional items. They require a very high accuracy in the designs and help produce the critical components, such as:
- Catheter connectors
- Drug delivery components
- Microfluidic devices
- Surgical clips
- Diagnostic cartridges
To produce all these tools, micron-level accuracy is required.
Requirement #2: Excellent Surface Finish
Do you know that medical tools require an excellent surface finish? It is due to hygienic requirements and the need for contamination-free surfaces in medical supplies. A quality surface finish can help:
- Prevent bacterial growth
- Improve sterilization
- Reduce friction
- Improve fluid flow
- Enhance appearance
Requirement #3: High Repeatability
A mold is famous for its high repeatability. It can produce hundreds of identical pieces of equipment with the same structure and design. Medical manufacturers also require high repeatability in:
- Consistent cavity filling
- Stable dimensions
- Uniform cooling
- Predictable shrinkage
- Minimal process variation
Requirement #4: Contamination Prevention
Medical equipment and plastic components can’t afford contamination. A slight contamination can cause infections. Therefore, you must consider the following designs.
- Corrosion-resistant steel
- Rust prevention
- Easy cleaning
- Venting that prevents particle buildup
- Smooth cavity surfaces
- Reduced dead zones
Tip #2: Select the Right Mold Material
The selection of steel materials for mold manufacturing is crucial. Different grades and types are discussed below.
| Mold Material | Avantages | Common Applications |
|---|---|---|
| Stainless Steel (420, S136) | Corrosion resistant, high polish | Medical devices, optical parts |
| H13 Tool Steel | Excellent wear resistance | High-volume production |
| P20 Steel | Cost-effective | Medium production volumes |
| Hardened Steel | Long mold life | Multi-million cycle molds |
Tip #3: Choose Medical-Grade Plastics
Medical equipment requires a different type of plastic. A variety of plastic models are used in injection molding in the medical industry.
You should choose the following medical-grade plastics based on the application.
| Matériau | Typical Applications |
|---|---|
| Polypropylène (PP) | Syringes, containers |
| Polycarbonate (PC) | Transparent medical housings |
| Polyéthylène (PE) | Tubing, bottles |
| ABS | Equipment housings |
| PEEK | Implantable components |
| Polyetherimide (PEI) | Sterilizable instruments |
| TPU | Flexible medical devices |
Tip #4: Understand Important Mold Design Components
There are different mold design components. We have added all the components below.
Mold Cavities
Cavities provide the spaces into which molten plastic is injected. There can be different cavities and designs. For example:
- Single cavity
- Multi-cavity
- Moules familiaux
- Moules à étages
Core Design
Code design is crucial for the internal structure of the components. It helps achieve:
- Epaisseur de paroi uniforme
- Better cooling
- Easier ejection
- Reduced sink marks
Runner System
Runner systems deliver molten plastic to the cavities. There are two runner systems, such as:
- Cold runners for smaller production
- Hot runners for high-volume production.
Gate Design
Gate selection matters because it determines the quality of the parts produced. The common configurations of the gate design add:
- Pin gate
- Tunnel gate
- Edge gate
- Fan gate
- Valve gate
Valve gates are commonly used in the medical industry.
Venting System
The Venting System maintains the design and provides accuracy. Without a venting system, here is what happens when air becomes trapped inside.
- Burn marks
- Coups courts
- Incomplete filling
- Gas traps
Cooling Channels
Cooling is a critical process that helps solidify the produced products. Well-designed cooling channels provide:
- Uniform temperature distribution
- Faster production
- Reduced warpage
- Better dimensional stability
Conformal cooling is the preferred choice in medical mold manufacturing.
Ejection Systems
The ejection system helps remove the finished products without causing damage. Here are a few ejection systems.
- Ejector pins
- Sleeve ejectors
- Air ejectors
- Stripper plates
Tip #5: Design for Sterilization
Medical tools must be sterilized after every use. Here are a few sterilization processes.
- Steam autoclave
- Ethylene oxide (EtO)
- Gamma radiation
- Electron beam
- Hydrogen peroxide plasma
Mold manufacturers must consider mold designs and part geometry to ensure stability during sterilization.
Tip #6: Design for Manufacturability (DFM)
If you want to simplify the design and production, consider design for manufacturability. It must ensure the following aspects.
- Epaisseur de paroi uniforme
- Proper draft angles
- Rounded corners
- Balanced filling
- Reduced undercuts
- Controlled shrinkage
- Optimized gate location
DFM detects issues before mold production and avoids critical errors later on.
Tip #7: Regulatory Considerations
Medical devices must comply with certain rules and regulations before they are available on the market.
It includes:
- ISO 13485 Quality Management System
- ISO 10993 Biocompatibility Evaluation
- Good Manufacturing Practices (GMP)
- FDA Quality System Regulation
When designing medical-grade injection molds, ensure they comply with all the above standards.
Conclusion
The medical industry relies on injection molds. The right design and consistent production ensure an excellent experience throughout the production of medical supplies. A slight error in the mold’s design can cause financial losses. Therefore, consider the design across various planning stages and choose the best one.
Are you looking for the premium injection molding design manufacturers? Contact Mold Partner. We have years of experience manufacturing injection molds and can help you design medical injection molds. You will achieve accuracy and precision and enjoy high-volume production with our techniques. Talk to our experts right away!
