Discover the differences between Low Pressure Molding (LPM) vs. Potting for protection in the Rail Industry to understand why modern manufacturers are shifting from conventional Potting to Low Pressure Molding (LPM) to guarantee reliable circuit board protection for sensors and cable harnesses against vibration and harsh environments.
Source: Internet
The modern Rail Industry is undergoing a massive digital transformation. From high-speed rolling stock to urban metro systems, today’s trains are essentially rolling data centers. They rely heavily on sensitive PCBs for operation, convenience, and safety.
Source: Internet
However, the operating environment in railway manufacturing is notoriously harsh. Electronic components must survive relentless high-G vibration, mechanical shock, extreme thermal cycling (-40°C to +85°C), moisture, and chemical exposure. Meanwhile, they must strictly adhere to rigorous safety standards, namely EN 50155 (electronic equipment on rolling stock).
To ensure optimal circuit board protection for these sensitive electronics in harsh environments, engineers have historically relied on conventional Potting.
But as the demand for lighter, faster, and more cost-effective production grows, a superior technology has emerged: Low Pressure Molding (LPM).
This technical article provides a comprehensive comparison to help you choose the best protection solution.
1. Drawbacks of Potting vs. Low Pressure Molding in the Rail Industry
Conventional Potting involves pouring a two-component (2K) liquid resin – typically polyurethane, silicone, or epoxy – into a pre-made plastic or metal housing containing the PCBs or sensors (Watch the process here).
While it provides excellent waterproofing, it leads to significant bottlenecks in railway manufacturing.
Find out the optimal usage of potting here.
1.1. Heavy Weight Penalties:
In the Rail Industry, weight reduction is a primary goal to improve energy efficiency and reduce track wear.
Potting inherently adds unnecessary weight because it requires a rigid outer housing (the “pot”) to hold the liquid resin.
Source: Internet
Furthermore, standard Potting resins are incredibly dense. When multiplied by hundreds of sensors across a train, this added mass becomes a significant operational penalty for the Rail Industry.
1.2. Slow Production Cycles:
Despite its chemical resistance, Potting is a slow, multi-step process.
Source: Internet
Once poured, the resin must cross-link to cure. While some resins cure at room temperature, accelerating this process for mass production in railway manufacturing often requires large, energy-intensive heating ovens.
This creates a massive bottleneck and a large footprint of Work-In-Progress (WIP) inventory, complicating the transition from Potting to Low Pressure Molding.
1.3. Component Stress and Damage:
During the chemical curing process of rigid 2K potting compounds, two dangerous phenomena often occur:
- Exothermic Reaction: The chemical reaction generates heat, which can damage sensitive microprocessors.
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- Shrinkage: As rigid resins cure, they shrink, exerting mechanical stress on fragile PCBs. Under the extreme vibration of a train bogie, this internal stress leads to solder fatigue and premature failure, a major concern in the Rail Industry.
2. Advantages of Low Pressure Molding Over Potting in the Rail Industry
Low Pressure Molding (LPM) is a drastically different technology. Watch the below video for a short and simple introduction.
It utilizes single-component, solvent-free thermoplastic polyamides. The material is heated to a liquid state and injected into a customized mold cavity containing the electronic component.
Here is why railway manufacturing engineers are aggressively transitioning to LPM:
2.1. Zero-Housing Encapsulation:
Low Pressure Molding eliminates the need for an external “pot”.
Source: Internet
The thermoplastic material forms its own structural outer shell as it cools. By removing the bulky plastic housing, manufacturers can reduce the overall weight and footprint of the encapsulated PCBs by up to 30-50%, a critical factor in aerodynamic rolling stock design.
Guidance to choose the right material for your application here.
2.2. Ultra-Fast Cycle Times (Seconds, Not Hours):
LPM is a physical phase change, not a chemical reaction.
The hot melt adhesive is injected into the mold and cures simply by cooling down within 10 to 60 seconds. The component can be immediately tested and assembled.
This eliminates curing ovens and brings lean manufacturing to the Rail Industry.
Source: Internet
2.3. Ultimate Circuit Board Protection:
As the name suggests, LPM operates at very low injection pressures – typically between 1.5 to 40 bar.
This gentle flow encapsulates the most fragile, bare PCBs and delicate glass sensors without causing physical deformation. Unlike potting, there is no exothermic heat or severe shrinkage to stress the components.
2.4. Superior Shock Absorption:
The polyamides used in Low Pressure Molding are engineered to be tough yet flexible.
Unlike rigid potting epoxies that can crack under mechanical vibration, LPM materials absorb and dampen train chassis shock while easily meeting IP67/IP68 waterproof standards for the Rail Industry.
3. Low Pressure Molding: Advanced Solution for Railway Manufacturing
The transition to LPM is unlocking new levels of reliability for print circuit board protection across various subsystems:
- Cable Harnesses and Connectors: Trains utilize miles of cabling. Low Pressure Molding is ideal for over-molding connectors, creating strain relief, and providing waterproof seals at wire junctions faster than traditional potting. Find more information about Low Pressure Molding for Cable here.
Product Recommendation: Thermelt® TH 858; HM3303
Source: Internet
- Bogie and Axle Sensors: Speed and vibration sensors mounted directly on bogies face the most brutal conditions. LPM provides the necessary shock absorption without adding the excess bulk of a potting housing.
Product Recommendation: Thermelt® TH 865
Source: Internet
- Trackside Signaling Systems: RFID tags, balises, and outdoor communication PCBs benefit from the rapid, UV-resistant encapsulation of Low Pressure Molding.
Product Recommendation: Thermelt® TH 858; Thermelt® TH 868
Source: Internet
4. Prostech: Strategic Partner of Rail Industry
Transitioning from conventional potting to Low Pressure Molding requires deep expertise in material science and mold design.
Source: Prostech
For B2B clients in railway manufacturing, Prostech is your end-to-end engineering partner.
- Expert Material Selection: We offer high-performance polyamides specifically formulated to meet the strict thermal and flame-retardant (UL94 V-0) requirements of the Rail Industry.
- Custom Mold Design: Our engineering team manufactures high-precision, low-cost aluminum molds tailored to the exact geometry of your PCBs and connectors.
- Scalable Equipment Integration: We provide robust LPM machines – from compact tabletop units to fully automated, inline systems for high-volume railway manufacturing.
Stop letting slow curing times and excess weight derail your production efficiency. Upgrade your circuit board protection strategy today.
Contact Prostech to schedule a technical consultation and discover how Low Pressure Molding can revolutionize your assembly line.
