The Role
Design and validate mechanical and electromechanical systems for GRID, an autonomous rebar-tying robot. Responsibilities include chassis, gantry, actuators, powertrain, terrain performance, CAD and drawing packages, structural analysis, prototyping, system testing, troubleshooting, DFM/DFA, manufacturing readiness, documentation, and mentoring engineers. The role collaborates across software, electrical, and manufacturing teams and supports field deployment and higher-volume production.
Summary Generated by Built In
Senior Mechanical Engineer
About the Company
About the Role
Responsibilities
Required
Preferred
Compensation & Benefits
About the Company
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.
About the Role
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.
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
Required
- 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
This is an in-person role, five days a week, in the San Francisco Bay Area. You must be based in the Bay Area or willing to relocate.
- 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
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.
We're a startup moving fast, and being in the room together is how we build.
- Daily lunches
- Flexible PTO
- Kaiser Gold HMO health plan
- Pet Friendly
Arn Autonomy is an Equal Opportunity Employer. All qualified applicants will receive consideration for employment without regard to race, color, religion, sex, gender identity or expression, sexual orientation, national origin, age, disability, veteran status, or any other characteristic protected by applicable law.
Skills Required
- 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 for mobile platforms, including sizing electric motors and gearboxes from system requirements
- Proficiency with at least two CAD packages, such as CATIA, SolidWorks, or Fusion
- Strong GD&T and tolerance-stack fundamentals
- Experience creating complete drawing packages for machined parts, BOMs, specifications, and engineering change documentation
- Practical knowledge of CNC machining and 3D printing and when to choose each
- Structural analysis skills, including hand calculations, FEA judgment, and optimization for strength and stiffness
- Experience taking hardware from prototype through design validation and low-volume production
- Strong hands-on prototyping, debugging, and testing skills
- Experience mentoring or guiding less experienced engineers
- Experience with mobile or outdoor robotic platforms, AMRs, construction or agricultural equipment, or off-road vehicles
- Experience with strength-optimized structures, topology optimization, load path design, high-strength aluminum and steel alloys, or composites
- Experience reading and interpreting patents; named inventor experience is a plus
- Experience with IP-rated enclosures for outdoor, dusty, or wet environments, reliability testing, and failure analysis
- Experience owning supplier relationships for machined parts or weldments
- Experience working in a fast-paced, early-stage startup
- Based in the San Francisco Bay Area or willing to relocate
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The Company
What We Do
CX2 (Cox Exponential) is the early stage venture vehicle for Cox Enterprises. Founded by technologists with decades of experience leading startups and building AI/ML products, CX2 partners with exceptional entrepreneurs and early stage companies to maximize their business potential.
