Ground User Terminals (Phased Array)

Ground User Terminals PC/ABS Blend Injection Molding with Sumitomo SE-EV-A 450T

As an engineer designing for the satellite communications sector, you operate at the unforgiving intersection of extreme environmental resilience and non-negotiable RF performance. For components like the radomes on Ground User Terminals (Phased Array), the material and manufacturing choices you make are not trivial; they are fundamental to the system's viability. These terminals are deployed in the world's harshest conditions—from the scorching heat of a desert to the frigid expanse of the arctic and the corrosive salt spray of maritime environments. The radome, the protective housing for the sensitive phased array antenna, must be a fortress against these elements while remaining perfectly transparent to the required RF frequencies. This dual-mandate creates a significant engineering challenge, one that often leads to compromises in design, material selection, or manufacturing cost.

The go-to material for this application is frequently a PC/ABS blend, and for good reason. A material like SABIC Cycolac MG47 offers a superb balance: the toughness and impact resistance of polycarbonate (PC) combined with the processability and aesthetic finish of acrylonitrile butadiene styrene (ABS). However, this is where the real-world manufacturing problems begin. PC/ABS blends are notoriously susceptible to high and non-uniform shrinkage, typically in the range of 0.4-0.7%. For a large, complex geometry like a radome, this material characteristic manifests as warpage, dimensional instability, and—most critically—sink marks over thick-walled sections like ribbing and bosses. These are not mere cosmetic blemishes. Warpage can prevent a proper IP-rated seal, while dimensional deviation across the radome surface can alter the RF path length, degrading beamforming accuracy and overall signal integrity. Sink marks create stress concentrations and weak points, compromising the part's long-term mechanical integrity. At MechanoFab, we have engineered a process that directly confronts and solves these inherent material challenges, leveraging a specific combination of Standard Injection Molding expertise and state-of-the-art equipment to deliver net-shape, dimensionally perfect components straight from the tool.

Conquering Compliance: A Process-Driven Approach

Meeting the stringent compliance standards of the satcom industry is not a final inspection step; it's a principle embedded in the entire manufacturing process. Our methodology using the Sumitomo SE-EV-A 450T is purpose-built to ensure your designs meet and exceed these requirements from the first shot.

• FCC Part 25 & RF Integrity: This standard governs satellite communications, and for a phased array, its performance is inextricably linked to the physical precision of the radome. The array's ability to accurately form and steer beams depends on a consistent dielectric medium and precise physical distance between the array elements and the outer world. Our process control eliminates the warpage and dimensional variability that can plague large PC/ABS parts. The shot-to-shot repeatability of the all-electric Sumitomo platform ensures that the geometric profile of every radome is identical, preserving the as-designed RF performance and guaranteeing that your system operates within its specified FCC parameters without signal degradation caused by manufacturing variance.

• IP67 Ingress Protection: An IP67 rating signifies a component is completely dust-tight and can withstand water immersion up to one meter. This is not achievable if the sealing surfaces of your radome are warped or inconsistent. Gasket channels and mating flanges must be perfectly flat and true to the CAD model to maintain compressive seal integrity over the product's lifetime. Traditional molding can result in a high scrap rate for parts that fail pressure decay or water ingress tests. Our process, by controlling and counteracting the material's natural tendency to warp, produces parts with pristine, dimensionally accurate sealing surfaces every single time. This eliminates the need for post-machining of flanges and drastically reduces the risk of field failures due to environmental ingress.

• UL746C (Outdoor UV Exposure): SABIC Cycolac MG47 contains a UV stabilization package, but this package can be compromised by improper processing. Excessive residence time or shear heat in the molding barrel can degrade the polymer and its additives, leading to premature yellowing, embrittlement, and failure when exposed to long-term sunlight. The Sumitomo SE-EV-A 450T's all-electric platform provides exceptionally precise thermal control throughout the plastication and injection cycle. We maintain the melt temperature within an incredibly narrow window, ensuring the material's intrinsic properties, including its UV resistance, are fully preserved in the final part. This guarantees compliance with UL746C for long-term outdoor suitability.

• RoHS Compliance: While primarily a material-level requirement, we enforce process-level purity. Our facility and the all-electric machine platform (which eliminates the risk of hydraulic fluid contamination) ensure that the RoHS-compliant SABIC Cycolac MG47 resin is not contaminated during manufacturing, guaranteeing a fully compliant final component.

Core Process & Material Specifications

To achieve this level of precision, every parameter is critical. Below is a top-level summary of the material, process, and machine specifications that define this capability. This is the foundation upon which we build dimensionally perfect, compliant ground terminal components.

Cost & Volume Dynamics: The TCO Advantage of Net-Shape Molding

For production volumes in the 1,000 to 50,000 unit range, the Total Cost of Ownership (TCO) becomes a far more critical metric than the simple per-part price. This is where our specialized process delivers a decisive economic advantage. The common industry practice for dealing with sink marks in PC/ABS is to accept them as an unavoidable defect, consigning parts to costly and labor-intensive secondary operations: filling, sanding, and painting. This not only adds significant cost and lead time but also introduces a potential point of failure. Warpage is often "managed" through complex cooling fixtures or by simply accepting a higher scrap rate. Our philosophy is to eliminate the problem at its source.

Processing PC/ABS blends for ground terminal radomes presents challenges with shrinkage and sink marks. Our approach leverages the Sumitomo SE-EV-A 450T's all-electric platform, providing the thermal stability and shot-to-shot repeatability needed to counteract the material's inherent 0.4-0.7% shrinkage and potential for warpage. The key advantage comes from Sumitomo's Z-Molding system, which allows for precise, responsive injection pressure control. This is not a simple "pack and hold" profile. Z-Molding is a closed-loop system that monitors cavity pressure in real-time and makes micro-adjustments to the injection screw's position and pressure during the cooling phase.

As the material begins to shrink and pull away from the mold wall in thick sections—the genesis of a sink mark—the Z-Molding system detects the subtle pressure drop and instantly commands the screw to push a precise, minute amount of additional melt into that specific area. This counteracts the shrinkage as it happens, holding the plastic against the mold surface until it is sufficiently solidified. This enables us to eliminate sink marks in thick-walled sections directly within the molding cycle, a common defect that often requires secondary fixes. The result is a net-shape, dimensionally stable component compliant with IP67 and UL746C standards in a single step.

This single-step, net-shape production methodology is the cornerstone of TCO reduction. By delivering a perfect part from the mold, we eliminate:

• Secondary Labor Costs: No filling, sanding, or cosmetic repair.
• Scrap Rate: Warpage and sink-related rejects are virtually eliminated.
• Inspection Overhead: Reduced need for complex CMM programs or fixtures to check for warpage.
• Supply Chain Complexity: No need to manage a secondary finishing vendor.

This streamlined workflow ensures that for production runs from 1,000 to 50,000 units, you benefit from the economies of scale of injection molding without the hidden costs of post-processing. We ensure perfect antenna alignment and environmental sealing without costly post-processing, delivering a lower total cost and a more reliable final product.

Conclusion: From Engineering Challenge to Manufacturing Certainty

Stop designing around the limitations of conventional molding. The challenge of producing large, dimensionally critical PC/ABS components for ground user terminals is solved. By pairing the right material with a process engineered for precision, we deliver radomes that meet every specification—mechanical, environmental, and electrical—straight out of the press. Let us help you move from prototype to production with confidence and cost-effectiveness.