What is LPM
- Core Concept
Low Pressure Molding employs extremely low injection pressure (typically 1.5–40 bar) and specialized hot-melt adhesive materials to fully or partially encapsulate and protect precision electronic components, circuit boards, wire harness connectors, and similar items at low temperatures.
Its process resembles “enveloping the product with gently melted adhesive,” rather than the traditional injection molding approach of “forcing plastic into the mold cavity under high pressure.”
- Key Differences from Traditional High-Pressure Injection Molding
| Characteristics | LPM | Traditional high-pressure injection molding
|
| Injection pressure | Extremely low (1.5 - 40 bar) | Very high (300 - 2000 bar) |
| Processing temperature | Lower (around 200°C) | Higher (varies by material, often above 250°C) |
| Material | Specialized Hot-Melt Adhesive (Polyamide-Based PA/Polyolefin-Based PO) | General-purpose engineering plastics (such as ABS, PC, PP, nylon) |
| Clamping force requirements | Extremely low, compact machine | Very tall, the machine is massive. |
| Stress on the product | Minimal, causing no damage to precision components | Larger, potentially damaging fragile components |
| Process | Mostly manual or semi-automatic placement of inserts | Fully Automatic Cycle |
- Three Core Advantages of Low-Pressure Injection Molding
- Exceptional Protective Properties:
Waterproof and Moisture-Resistant: Forms seamless seals achieving IP67 or higher protection ratings.
Chemical Resistance: Withstands exposure to oils, salt spray, cleaning agents, and more.
Insulation and Shock Absorption: Cushions mechanical impacts and vibrations while providing electrical insulation.
- Gentle on precision components:
Low-pressure, low-temperature processes generate minimal stress, preventing damage or displacement of precision sensors, microelectronic components, and solder joints.
Ideal for components that cannot be repaired after encapsulation.
- Short cycle time: Rapid material curing.
No expensive molds required: Low pressure allows use of aluminum molds or even simple mold frames, reducing costs and lowering barriers for small-batch production.
High design flexibility: Capable of encapsulating irregularly shaped components with integrated cables.
- Process Flow Overview
Preparation: Manually or automatically place electronic components (inserts) requiring encapsulation into the lower mold cavity.
Mold Closing: The mold closes with minimal pressure applied.
Injection Molding: Specialized low-temperature hot melt adhesive is heated to a molten state and slowly injected into the cavity under low pressure, gradually enveloping the components.
Pressure Holding and Cooling: After a brief pressure holding period, the material rapidly solidifies.
Mold Opening and Part Removal: The perfectly encapsulated integrated component is removed.
Summary
Low-pressure injection molding is a “gentle and precise” plastic encapsulation technology. Its core value lies in:
Providing delicate electronic components with robust “protective armor” under minimal mechanical and thermal stress, delivering triple protection through sealing, insulation, and shock resistance.