Exoskeletons

Exoskeletons ULTEM 9085 Fused Deposition Modeling (FDM) with Stratasys F370

As engineers designing for the human-machine interface, we operate at the brutal intersection of uncompromising performance and biological reality. For developers of Exoskeletons, this challenge is magnified to an extreme. Whether for medical rehabilitation, industrial load-bearing, or military force augmentation, the core engineering problem remains the same: how do you create a structure that is simultaneously lightweight enough for human integration, strong enough to bear immense loads, and complex enough to mimic biomechanical articulation, all while being safe and manufacturable?

For decades, the default answer has been meticulously machined titanium and high-grade aluminum alloys. While these materials offer phenomenal strength-to-weight ratios, they impose a punishing tax on the manufacturing process. The complex, organic geometries of exoskeleton joints, brackets, and structural housings are a nightmare for subtractive methods. CNC machining these parts from billet results in staggering buy-to-fly ratios, where the majority of your expensive material block is reduced to chips on the floor. Tool wear is significant, cycle times are long, and any design iteration means going back to the drawing board for CAM programming and fixture design, adding weeks or months to development cycles. This friction has been a persistent bottleneck, slowing innovation in a field that desperately needs to move faster.

This is where a paradigm shift in manufacturing strategy becomes not just advantageous, but necessary. We are moving beyond metal. The solution lies in leveraging a high-performance thermoplastic, a process that can tame its demanding nature, and a deep understanding of Design for Additive Manufacturing (DfAM). By combining the incredible properties of ULTEM 9085 (FDM) with the industrial precision of Fused Deposition Modeling (FDM) on a purpose-built platform, we can bypass the limitations of traditional fabrication entirely. This isn't about 3D printing toys; it's about producing production-grade, mission-critical hardware directly from a digital file.

Engineering for Compliance: ISO 13485, MIL-STD-810G, and CE MDR

In the high-stakes world of exoskeletons, a part is only as good as its compliance dossier. Simply meeting mechanical specifications is insufficient. The manufacturing process itself must be robust, repeatable, and traceable. Our specific combination of ULTEM 9085 and the Stratasys F370 is architected to meet these stringent demands head-on.

For Medical Rehabilitation (ISO 13485 & CE MDR): The ISO 13485 standard for medical device quality management systems hinges on process validation and traceability. The Stratasys F370 provides an unparalleled digital thread. From the moment a CAD file is loaded, every critical process parameter—nozzle temperature, chamber temperature, material feed rate, layer height—is monitored and logged. Material spools are barcoded, allowing for precise batch tracking from the raw polymer resin to the final part. This creates a robust, auditable Device History Record (DHR) that is essential for regulatory submissions to bodies like the FDA or for CE marking under the European Medical Device Regulation (MDR). ULTEM 9085 resin itself is biocompatible (ISO 10993 and USP Class VI certified) and can be sterilized using EtO, hydrogen peroxide, or gamma radiation methods, making it suitable for applications with patient contact. The inherent FST (Flame, Smoke, Toxicity) rating of the material further bolsters the safety case required by the MDR's General Safety and Performance Requirements (GSPR).

For Military & Defense (MIL-STD-810G): Military applications demand survival in the harshest environments. MIL-STD-810G is not a single specification but a suite of brutal tests designed to simulate the lifecycle of equipment in the field. Key tests for exoskeleton components include:

• Method 501.7 (High Temperature) & 502.7 (Low Temperature): ULTEM 9085 possesses a high glass transition temperature (Tg) of 186°C and a heat deflection temperature of 153°C. This means it retains its structural integrity and mechanical properties in operating environments that would cause lesser polymers to soften and fail.
• Method 514.8 (Vibration) & 516.8 (Shock): This is where the manufacturing process is as critical as the material itself. A part's ability to withstand shock and vibration is directly tied to its inter-layer adhesion. Printing ULTEM 9085 without a heated chamber results in poor layer bonding, creating a part that is fundamentally flawed and will delaminate under stress. The F370's fully enclosed, heated build chamber is the critical enabler, ensuring robust, near-isotropic Z-axis strength that allows the printed component to behave as a monolithic whole, surviving the intense vibratory and shock loads encountered in military operations. The material's FST rating is also a non-negotiable requirement for use within vehicles and on personnel.

By wedding a high-performance, pre-certified material with a tightly controlled and traceable industrial process, we deliver components that are not just mechanically sound, but certifiable for the most demanding applications on Earth.

Technical Specifications: Material and Process Parameters

To make informed design decisions, you need hard data. The following table outlines the key physical properties of ULTEM 9085 as printed on our system, alongside the precision and limitations of the Stratasys F370 platform. This is the operational envelope within which we can create your components.

The Economic & Engineering Advantage: Taming Thermal Stress

The datasheet properties of ULTEM 9085 are impressive, but they are meaningless if the manufacturing process cannot translate them into a physical part. Printing this material is notoriously difficult, and this difficulty is rooted in fundamental materials science. With a glass transition temperature of 186°C, the filament must be extruded at temperatures exceeding 350°C. When this molten material is deposited onto a cooler layer or an unheated build platform, the massive temperature differential (ΔT) induces extreme internal stresses. These stresses manifest in two catastrophic failure modes: warping, where the part curls and lifts off the build plate, and delamination, where the layers themselves fail to fuse and pull apart.

This is not a problem that can be solved with a simple enclosure or a heated bed. It requires an active, precisely controlled thermal environment. Our advantage stems from the Stratasys F370's fully enclosed and heated build chamber. This feature is not a luxury; it is a non-negotiable requirement for success with high-Tg materials. The chamber maintains a stable ambient temperature across the entire build volume, keeping the part elevated just below its glass transition temperature throughout the entire printing process. This simple-sounding feat has profound engineering consequences:

1. Stress Mitigation: By minimizing the ΔT between the nozzle and the part, it prevents the buildup of internal stresses, virtually eliminating warp and ensuring dimensional stability even on large, flat components.
2. Enhanced Inter-Layer Adhesion: Keeping the previous layer warm allows the newly deposited material to achieve superior thermal fusion and polymer chain entanglement. This is the critical mechanism for achieving robust Z-axis strength, transforming a stack of individual layers into a truly monolithic, load-bearing structure.

This process mastery unlocks a powerful economic advantage, particularly in the low-volume production space optimized for 1-20 units. For exoskeleton development, this volume is the sweet spot for prototyping, fitting trials, and low-rate initial production (LRIP). Consider the total cost of ownership (TCO) when comparing our additive process to traditional CNC machining of a complex titanium exoskeleton joint:

• Subtractive CNC (Titanium): The process begins with an expensive block of Ti-6Al-4V. A 5-axis programmer spends days developing complex toolpaths and designing custom fixtures. The machining itself is slow due to titanium's poor thermal conductivity and toughness, leading to high tool wear and long machine hours. A significant portion—often over 80%—of the initial material is machined away. The final TCO is dominated by skilled labor, machine time, tooling costs, and wasted material. A single design change resets this entire expensive cycle.

• Additive FDM (ULTEM 9085): The process begins with a digital file. Part preparation takes a few hours, focusing on strategic orientation to manage Z-axis loads and optimize support structures. The part is then printed directly to its final, net-shape geometry in a "lights-out" operation. Material waste is negligible, limited only to the soluble support structures. There is zero tooling cost. The F370's auto-switching material bays allow for continuous, unattended builds. The result is a lightweight, FST-rated, and incredibly strong component produced in days, not weeks.

By leveraging this single-step additive process, we can integrate features impossible with machining—internal lattice structures for optimized light-weighting, consolidated multi-part assemblies into a single print, and integrated channels for wiring or hydraulics. This allows you to deliver a more functional, lighter, and more advanced product to market or to the field faster than your competition. The ability to produce a custom-fit, mission-ready component right off the build plate is a force multiplier for innovation.

Conclusion: Accelerate Your Exoskeleton Program

The challenge of building next-generation exoskeletons demands a manufacturing approach that is as advanced as the designs themselves. By mastering the difficult science of printing ULTEM 9085 within the thermally controlled environment of the Stratasys F370, MechanoFab offers a direct path to producing lightweight, high-strength, and certifiable components. We eliminate the punishing overhead of traditional machining for complex parts, collapsing development cycles and enabling rapid iteration. Move beyond the limitations of metal and start building the future of human augmentation. Upload your design and let us show you what is possible.