Choosing the right method for your project
While traditional injection molding remains the preferred solution for many high-volume plastic components, it is not always the best fit. Low pressure molding offers a unique alternative that protects sensitive components while reducing tooling costs and simplifying production.
Understanding the differences between these two manufacturing methods can help determine which process best aligns with your application.
What Is Low Pressure Molding?
Low pressure molding is an overmolding process that uses specialized hot-melt polyamide materials injected at significantly lower pressures than conventional thermoplastic injection molding.
Rather than creating a standalone plastic housing, low pressure molding encapsulates or seals an existing component, such as:
- Printed circuit boards (PCBs)
- Wire harnesses
- Connectors
- Sensors
- Electronic assemblies
- Medical components
- Industrial control devices
The lower injection pressure minimizes mechanical stress during manufacturing, making it ideal for protecting delicate assemblies that could be damaged in a traditional molding process.
How Traditional Injection Molding is Different from Low Pressure
Traditional injection molding injects molten thermoplastics into hardened steel or aluminum tooling at very high pressures. The process is ideal for producing rigid plastic components with excellent dimensional consistency and repeatability.
It excels when manufacturing:
- Plastic housings
- Structural components
- Consumer products
- Automotive parts
- Medical equipment enclosures
- Industrial equipment components
Traditional injection molding is often the best solution for high-volume production where part geometry, material selection, and production efficiency justify the investment in tooling.
However, those higher injection pressures can present challenges when molding directly around fragile electronic components or assemblies.
Is Low Pressure Molding the Better Choice?
While both processes have important roles in manufacturing, several application requirements make low pressure molding the preferred option.
You Need to Protect Sensitive Electronics
One of the biggest advantages of low pressure molding is its ability to encapsulate delicate components without exposing them to excessive pressure while molding.
The hot-melt polyamide materials flow easily around components while placing minimal stress on solder joints, connectors, sensors, and circuit boards.
This protective layer helps guard against:
- Moisture
- Dust
- Dirt
- Chemicals
- Mechanical vibration
- Strain on cable connections
For products operating in harsh industrial environments, this added protection can improve long-term reliability.
Tooling Costs Need to Stay Lower
Traditional injection molding often requires complex hardened tooling capable of withstanding high injection pressures.
Low pressure molding generally uses simpler tooling because of the significantly lower molding pressures involved. For many projects, this results in:
- Lower initial tooling investment
- Faster tooling production
- Easier design revisions
- Reduced development costs
For lower production volumes, prototypes, or specialized assemblies, these savings can be substantial.
You Want to Eliminate Secondary Assembly Steps
Many electronic products require multiple manufacturing operations, including installing seals, strain reliefs, protective housings, adhesives, or potting compounds.
Low pressure molding can often combine several of these functions into a single molded component.
Benefits include:
- Fewer assembled parts
- Reduced labor
- Improved consistency
- Better environmental sealing
- Simplified supply chains
Consolidating multiple manufacturing steps into one process can reduce opportunities for assembly errors while improving overall production efficiency.
Complex Geometries Need Reliable Sealing
Low pressure molding materials naturally flow around irregular shapes, connectors, wires, and complex assemblies.
This makes the process particularly effective when components have:
- Multiple cable exits
- Intricate connector geometries
- Tight spaces
- Mixed materials
- Difficult sealing surfaces
Instead of requiring separate gaskets or sealing methods, the molded material creates a protective encapsulation around the entire assembly.
When Traditional Injection Molding Makes More Sense
Although low pressure molding offers several advantages, traditional injection molding remains the better solution for many applications.
Injection molding is typically preferred when:
- Manufacturing rigid structural plastic parts
- Producing very high production volumes
- Tight dimensional tolerances are required
- Engineering-grade thermoplastics are necessary
- Cosmetic surface finishes are important
- Large plastic housings are being manufactured
If the molded component itself serves as the final structural product, traditional injection molding generally provides greater material flexibility and production efficiency.
Key Questions Engineers Should Ask
Choosing between these processes starts with understanding the application’s requirements.
Consider the following questions during product development:
- Does the assembly contain delicate electronics?
- Is environmental sealing required?
- Will the molded material primarily protect the component rather than provide structural strength?
- Are tooling costs a significant project concern?
- Can multiple assembly steps be consolidated?
- What production volume is expected?
- What materials are required for the final application?
Answering these questions early helps determine which manufacturing process will provide the best balance of performance, cost, and manufacturability.
Find the Right Manufacturing Process for Your Application
There is no universal answer to whether low pressure molding or traditional injection molding is better. Each process serves different design objectives.
Reach out to the Felton team to get support throughout the product development process by combining engineering expertise with integrated manufacturing capabilities, including low pressure molding, overmolding, injection molding, machining, forming, welding, and assembly.