The plastic injection molding industry is experiencing unprecedented demand for micro parts — components weighing mere milligrams with tolerances measured in microns — driven by the booming healthcare and medical device sectors. In 2024, the global medical micro injection molding market was valued at $596.7 million, projected to reach $1,662.8 million by 2033, with a compound annual growth rate (CAGR) of 12.2%. This growth is fueled by the rising prevalence of chronic diseases, an aging population, and the need for miniaturized components in applications like bio-absorbable implants, diagnostic sensors, and wearable devices. Producing these micro parts requires manufacturing processes that deliver exceptional quality, minimal waste, and scalability. Traditional cold runner systems often lead to material inefficiencies and inconsistent quality, creating challenges for moldmakers and manufacturers. MHS Hot Runners, a division of Westfall Technik, introduces a groundbreaking direct-gating micro molding solution that redefines industry standards through precision, efficiency, and sustainable innovation. This blog post explores how this technology achieves near-instantaneous cavity filling, superior part properties, and automated efficiency, empowering decision-makers to meet the challenges of micromolding head-on.
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The Micro Molding Challenge
Producing micro parts, such as bio-absorbable implants or electronic connectors, demands precision far beyond conventional molding.
Key challenges include:
• Tight Tolerances: Dimensional accuracy within a few microns is essential, as even minor deviations can render parts unusable. For context, a human hair is approximately 100 microns thick.
• Material Efficiency: Cold runner systems generate significant waste, often requiring runners 10 times the weight of the part itself, increasing costs for high-value polymers like PEEK or LCP.
• Part Quality: Slow melt flow in traditional systems creates frozen layers, leading to non-uniform polymer morphology, reduced density, and compromised feature replication.
• Scalability: High-cavitation molds producing millions of parts annually require robust, automated processes to maintain consistency without sacrificing speed.
These hurdles necessitate a paradigm shift in micromolding technology, prioritizing precision, waste reduction, and process control.
A New Era of Direct Gating
MHS Hot Runners’ advanced micromolding system, powered by the M3 machine, leverages a patented direct-gating process to eliminate cold runners, delivering micro parts with unparalleled quality and efficiency. This technology, designed for high-cavitation molds, integrates sophisticated engineering and automation to address the industry’s most pressing needs. Below, we outline its core innovations.
1. Near-Instantaneous Cavity Filling
The system employs a three-step injection process that fills micro cavities in 10–20 milliseconds, achieving near-instantaneous results. Unlike conventional machines that rely on plunger-driven melt, this process uses controlled melt expansion:
• Compressed Melt Dynamics: Plastic pellets are conditioned, melted, and compressed by 5–10% in a specialized screw and integrated hot runner system. This compression stores visco-elastic energy, which is released as high-velocity flow when the valve gate opens.
• Precision Valve Gating: With gate diameters as small as 0.5 mm, the system ensures rapid cavity pressure buildup, minimizing temperature and pressure gradients. This results in near-isobaric and isothermal conditions, critical for uniform part formation.
This approach enables the production of parts as small as 0.040 g, such as PEEK bone screws, with flawless replication of complex features.
2. Superior Part Quality
The direct-gating process enhances the molecular and physical properties of micro parts, addressing common quality issues:
• Shear-Thinning and Molecular Alignment: High injection speeds induce shear-thinning, reducing melt viscosity and aligning polymer molecules. This creates a robust skin-core structure, ideal for thin-walled features in medical or electronic components.
• Increased Material Density: Elevated melt pressure raises the solidification temperature, producing denser parts with reduced shrinkage and minimal frozen stress. Lab tests confirm that this process yields parts with improved density compared to raw plastic granules.
• Melt Integrity: Continuous pressure in the hot runner prevents molecular degradation by limiting free volume, solving residence time issues that plague materials like POM or LCP.
These advancements ensure consistent replication of micro features, such as those in hearing aids or precision connectors, meeting stringent industry standards.
3. Zero Waste and Cost Efficiency Through Green Innovation
By eliminating cold runners, the system achieves zero-scrap production, a cornerstone of Green Innovation. This approach significantly reduces material waste—traditional systems waste up to 90% of material on runners for a 10 mg part—lowering costs for expensive polymers like PEEK and minimizing environmental impact. Hot runners also reduce energy consumption by eliminating the need to cool and reprocess runners, cutting greenhouse gas emissions associated with material production and disposal. Faster cycle times further enhance energy efficiency, making this technology a sustainable choice for high-volume production.
4. High-Cavitation Versatility
The system supports molds with 8, 16, or 32 cavities, scalable to 32 cavities via small subrunners. It can inject two different part designs simultaneously in one cycle or handle two-shot, multi-material, and overmolding processes. This flexibility accommodates diverse applications, from medical implants to electronic circuit board components.
5. Automation and Operator-Friendly Design
Built for high-volume production, the system integrates advanced automation and safety features:
• Rapid Cycle Times: A dry cycle time under 3 seconds maximizes throughput, supported by an electric linear motor with speeds up to 6,000 mm/s and micron-resolution torque feedback.
• Touchless Robotics: A vacuum-based takeout system handles parts individually, ensuring seamless downstream processing. Optional vision inspection monitors cavities twice per cycle for quality control.
• Modular Design: Small mold inserts can be swapped in minutes by a single operator, facilitating a smooth transition from prototyping to mass production. A tiebar-less design offers unobstructed access for robots and auxiliary equipment.
• Clean Room Readiness: Electromatic machines are shipped clean room-ready with optional HEPA filters, ideal for medical applications.
An intuitive touchscreen interface centralizes control, enhancing user-friendliness and data transparency.
Industry Impact
This direct-gating technology transforms micro molding by delivering:
• Cost Savings: Zero-scrap production and faster cycles reduce material and operational expenses.
• Unmatched Quality: Denser, stronger parts with precise feature replication meet the demands of medical, electronics, and healthcare industries.
• Scalability: High-cavitation molds and automated systems support mass production of millions of parts annually.
• Green Innovation: By eliminating runner waste and reducing energy use, hot runners align with circular economy goals, minimizing the healthcare sector’s 4.4% contribution to global greenhouse gas emissions and supporting sustainable manufacturing practices.
For decision-makers, this solution offers a competitive edge, enabling the production of complex micro parts—like bio-absorbable implants or precision connectors—with efficiency, reliability, and environmental responsibility.
