Exoskeletons

Exoskeletons ULTEM 9085 Fused Deposition Modeling with Stratasys F900

As engineers designing the next generation of human augmentation systems, we operate at the unforgiving intersection of biomechanics, materials science, and robotics. The components we create for Exoskeletons must be impossibly strong yet lightweight, intricately complex to match human anatomy, and robust enough to withstand extreme operational environments, from the sterile corridors of a rehabilitation clinic to the unpredictable terrain of a military theater. For years, the default solution for critical structural components like actuator housings, complex joint assemblies, and custom-fit chassis elements has been subtractive manufacturing—hogging out blocks of 6061-T6 aluminum or titanium. This approach, while proven, is a notorious bottleneck, characterized by high material waste, long CAM programming cycles, and exorbitant costs, especially for the low-volume, high-mix production typical of this field.

The promise of additive manufacturing has always loomed as a potential solution, but the reality has often fallen short. Standard desktop or even prosumer 3D printers simply cannot handle the high-performance polymers required for these load-bearing applications. This is where the specific, targeted combination of a superior material and an industrial-grade machine becomes not just an advantage, but a necessity. We're talking about producing parts with ULTEM 9085 (FDM), a polyetherimide (PEI) thermoplastic renowned for its high strength-to-weight ratio, FST (flame, smoke, and toxicity) rating, and exceptional thermal and chemical stability. However, printing with ULTEM 9085 is a masterclass in thermal engineering. Its high glass transition temperature (Tg) of 186°C makes it incredibly susceptible to thermal-stress-induced warping and delamination on any machine without precise environmental control. This is the core engineering problem we have solved. By leveraging Fused Deposition Modeling (FDM) exclusively on the Stratasys F900, we transform a challenging material into a game-changing manufacturing solution. The F900's actively heated build chamber is the key, allowing us to maintain a consistent, elevated temperature throughout the entire build cycle. This neutralizes internal stresses as they form, resulting in unparalleled inter-layer bonding and producing parts with near-isotropic mechanical properties. The result is a final component that rivals the performance of machined metal in many applications, delivered faster and with geometric freedom that CNC simply cannot match.

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

For exoskeleton components, a part is only as good as its qualification. Our process is engineered from the ground up to support the rigorous validation required by the world's most demanding regulatory bodies.

ISO 13485 & CE MDR (Medical Device Quality Management): For medical and rehabilitative exoskeletons, compliance with ISO 13485 and the European CE Medical Device Regulation (MDR) is non-negotiable. These standards demand a robust Quality Management System (QMS) with an intense focus on risk management, traceability, and process validation. This is where the industrial-grade nature of the Stratasys F900 becomes a critical enabler.

• Process Repeatability: The F900's thermally stable environment and precise motion control systems ensure that the 1st part, the 10th part, and the 20th part are dimensionally and mechanically identical within a tightly controlled process window. This high degree of repeatability is fundamental to process validation (PV) and operational qualification (OQ). We can provide the data to prove that our manufacturing process is stable and consistently produces parts that meet the design specifications, a cornerstone of any ISO 13485 audit.
• Material Traceability: We use Stratasys-certified ULTEM 9085 filament, which comes with complete lot traceability from the raw PEI resin to the final sealed spool. This unbroken chain of documentation is essential for the device's technical file and is a key requirement for both ISO 13485 and CE MDR. In the event of a field issue, we can trace the exact batch of material used for any given component.
• Biocompatibility: While ULTEM 9085 itself carries certifications for biocompatibility (ISO 10993/USP Class VI), the manufacturing process must not compromise this. The closed-system nature of the F900 and our stringent handling protocols ensure that no contaminants are introduced during the build process, preserving the material's inherent biocompatible properties for skin-contacting chassis and brace components.

MIL-STD-810G (Military Environmental Engineering): When exoskeletons are destined for military or defense applications, they must be proven to survive, not in a lab, but in the harshest conditions imaginable. MIL-STD-810G is a series of brutal environmental tests, and our ULTEM 9085 parts are uniquely suited to pass them.

• Thermal Shock & High Temperature (Methods 503.5 & 501.5): With a maximum service temperature of 153°C and a heat deflection temperature even higher, ULTEM 9085 components will not deform or degrade when left in a desert vehicle or during rapid temperature transitions. The superior inter-layer bonding achieved in the F900 prevents delamination, which is a common failure mode for lesser FDM parts under thermal shock.
• Mechanical Shock & Vibration (Methods 516.6 & 514.6): This is where near-isotropic properties are mission-critical. A typical FDM part is significantly weaker in the Z-axis (between layers) than in the XY-plane. This anisotropy creates a predictable failure point under shock or sustained vibration. Because our process minimizes internal stresses and maximizes layer fusion, the Z-axis strength of our ULTEM 9085 parts is dramatically improved. This means the complex geometries of a joint or actuator housing can withstand the g-forces and vibrational fatigue of being mounted on a vehicle or worn by a soldier in action, behaving more like a solid, injection-molded part.
• Chemical & Fluid Resistance (Method 504.1): PEI is inherently resistant to a wide range of chemicals, including fuels, hydraulic fluids, and cleaning agents commonly found in military environments. This ensures the material integrity and mechanical properties of the exoskeleton components are not compromised by incidental exposure.

Technical Specifications: Material & Machine Parameters

To make informed design decisions, you need hard data. The following table outlines the key performance indicators for our ULTEM 9085 components produced on the Stratasys F900. These are not theoretical maximums; they are the baseline properties you can expect from our qualified process.

Cost Dynamics vs. CNC Machining: The TCO Advantage

The economic sweet spot for this service is the low-volume production of 1-20 units. This range perfectly captures the needs of prototyping, clinical trials, and the creation of custom-fit devices tailored to individual users. While the per-part cost of an additively manufactured ULTEM 9085 component might seem higher than a simple FDM print in PLA or ABS, it represents a radical reduction in Total Cost of Ownership (TCO) when compared to its true alternative: multi-axis CNC machining of complex parts from metal billets.

Let's break down the cost avoidance. The challenge of printing with high-performance PEI filaments like ULTEM 9085 is centered on thermal management. Its high glass transition temperature causes immense internal stress during cooling on standard machines, leading to catastrophic warping and weak, delaminated layers. This is a non-starter for any serious engineering application. Our entire FDM workflow is architected around the Stratasys F900 specifically to solve this problem. Its actively heated build chamber creates a thermally stable environment, holding the entire part just below its Tg during the build. This is our key to neutralizing internal stresses in real-time. This process allows us to achieve exceptional inter-layer bonding, producing net-shape exoskeleton components with near-isotropic properties that are far superior to typical FDM parts.

For our clients, this translates directly into bypassing the costly and time-consuming workflow of multi-axis CNC machining. Consider a complex exoskeleton hip joint. Machining this from a block of aluminum involves:

1. Extensive CAM Programming: Hours or days for a skilled programmer to develop complex 5-axis toolpaths.
2. Material Waste: Potentially 80-90% of an expensive metal block is machined away into chips.
3. Multiple Setups & Fixturing: The part may need to be re-fixtured multiple times, introducing opportunities for error.
4. Long Machine Times: Hours of spindle time on a high-value machine tool.

With our F900 process, we print the net-shape part directly from your CAD file, often in a single, unattended run. The geometric complexity is essentially free. Internal channels for wiring, conformal lattices for weight reduction, and organic, ergonomic surfaces are all produced with no additional manufacturing cost. The process repeatability we achieve at MechanoFab is fundamental for delivering parts qualified for demanding applications, including those requiring ISO 13485 compliance. This additive approach drastically reduces lead time from weeks to days and liberates designers from the constraints of traditional manufacturing, enabling the creation of more efficient, integrated, and higher-performing exoskeleton systems.

Your Partner in Advanced Manufacturing

In the high-stakes world of exoskeleton design, material and process selection can define the line between a functional prototype and a field-ready, certified product. By combining the superior properties of ULTEM 9085 with the industrial precision and thermal control of the Stratasys F900, we offer a direct manufacturing path for your most complex and critical components. Move beyond the limitations of desktop printing and the prohibitive costs of CNC machining. Let's build the future of human augmentation, together.