Senior Mechanical Engineer at Arn Autonomy

Cox Exponential • South San Francisco, CA

7h • $90,000 - $165,000 • Onsite

About The Position

Arn Autonomy is building autonomous, non-humanoid robotic systems to construct infrastructure in extreme, unstructured environments, starting with next-gen construction job sites. Our vision is to disrupt the $16 trillion global construction industry by pioneering a new Deep Tech philosophy that blends robotics, AI, and systems engineering at the frontier. Our flagship product, GRID, is an autonomous rebar-tying robot deployed with rebar and concrete contractors on live job sites.

We're seeking a Senior Mechanical Engineer to join the team building GRID, our rebar-tying mobile robot, and to mentor colleagues on mechanical and electromechanical design. This is a hands-on, cross-disciplinary role spanning mechanical design, electromechanical integration, prototyping, and system-level testing on real hardware. You'll work on the tying mechanism, gantry, chassis, and powertrain, and partner closely with our software, electrical, and manufacturing teams to turn them into a working, testable robot. As an early hire, you'll help shape how we design, build, and validate hardware for field deployment and higher-volume manufacturing.

Requirements

• 5+ years of professional experience in mechanical engineering, robotics, or electromechanical systems, including shipping real hardware to customers or into the field
• Hands-on experience designing electromechanical assemblies (motors, actuators, gear trains, bearings, sensors, cable routing) for mobile platforms, including sizing electric motors and gearboxes from system requirements such as payload, speed, slope, and duty cycle
• Proficiency with at least two CAD packages (for example CATIA, SolidWorks, Fusion, or similar), with strong GD&T and tolerance-stack fundamentals
• Experience turning 3D models into complete drawing packages for machined parts, plus BOMs, specifications, and engineering change documentation; practical knowledge of CNC machining and 3D printing and when to choose each
• Structural analysis skills: comfortable sizing components by hand calc, knowing when to run FEA, and optimizing structures for strength and stiffness
• Experience taking hardware from prototype through design validation and low-volume production, with strong hands-on prototyping, debugging, and testing skills
• Experience mentoring or guiding less experienced engineers, for example through design reviews or day-to-day technical guidance. Formal management experience is not required

Nice To Haves

• Experience with mobile or outdoor robotic platforms (AMRs, construction or ag equipment, off-road vehicles), including an understanding of how wheeled or tracked chassis behave over uneven terrain with gaps and holes
• Experience with strength-optimized structures (topology optimization, load path design, high-strength aluminum and steel alloys, composites)
• Experience reading and interpreting patents; named inventor on patents is a plus
• Experience with IP-rated enclosures for outdoor, dusty, or wet environments, and with reliability testing and failure analysis
• Experience owning supplier relationships for machined parts or weldments, and working in a fast-paced, early-stage startup

Responsibilities

• Mechanical & Electromechanical Design: Design and specify the mechanisms, gantry, chassis, and actuators for a mobile robot operating in outdoor construction environments. Design for durability, serviceability, and performance across outdoor temperatures, dust, vibration, and weather
• Powertrain Design: Size and select electric motors and gearboxes from vehicle-level requirements such as payload, speed, slope, duty cycle, and torque margins
• Terrain Performance: Analyze and validate how the chassis behaves on uneven ground, including gaps and holes in rebar mats and decks (stability, ground clearance, wheel or track geometry, loads on the frame)
• Electromechanical Integration: Integrate motors, sensors, bearings, cabling, and power transmission into robust, field-ready assemblies, using both off-the-shelf and custom components
• Manufacturing Documentation: Turn 3D models into complete drawing packages for machined parts (GD&T, materials, finishes, inspection requirements), and design parts for 3D printing where appropriate
• Prototyping & Validation: Build and instrument prototypes and test setups. Optimize chassis and structural components for strength and stiffness, and run structural analysis (hand calcs and FEA) on critical load-bearing components to validate designs under real operating conditions
• System-Level Testing & Root Cause Analysis: Plan and run system-level tests on GRID; commission, operate, and troubleshoot mechanical subsystems. Identify likely root causes of system issues and failures, and engage the responsible team to drive resolution
• Cross-Functional Collaboration: Work closely with software, electrical, and manufacturing partners; take ownership of specific design and test tasks and bring your expertise to troubleshoot issues as they arise
• Mentorship & Design Guidance: Mentor and support colleagues on mechanical and electromechanical design, including design reviews and good practice in CAD, drawings, and tolerancing
• Manufacturing Readiness: Lead DFM/DFA efforts for machined, 3D-printed, and welded parts, and build test fixtures and procedures to scale toward field deployment and higher-volume production
• Documentation & IP: Document designs, test procedures, and results for traceability and knowledge sharing; contribute to patent work, including invention disclosures and prior-art review

Benefits

• Salary range: $90,000 - $165,000, depending on experience, plus equity.
• Pay offered may vary depending on multiple individualized factors, including market location, job-related knowledge, skills, and experience.
• The total compensation package for this position may also include other elements depending on the position offered; details will be provided if you receive an offer of employment.
• Daily lunches
• Flexible PTO
• Kaiser Gold HMO health plan
• Pet Friendly

What This Job Offers

• Job Type: Full-time
• Career Level: Senior
• Education Level: No Education Listed