Principal Mechanical Engineer

Commonwealth Fusion Systems is on a mission to deliver the urgent transition to fusion energy.

Combining decades of research, top talent, and new technologies, we're designing and building commercially viable fusion power plants. And working with policymakers and suppliers to build the energy industry of the future.

We're in the best position to make it happen. Since 2018, we've raised nearly $3 billion in capital, making us the largest and leading private fusion company in the world.

Now we're looking for more thinkers, doers, builders, and makers to join us. People who'll bring new perspectives, solve tough problems, and thrive as part of a team.

If that's you and this role fits, we want to hear from you.

Join the power movement as a Principal Mechanical Engineer

We're looking for a Principal Mechanical Engineer to join our R&D and equipment design team to help build the next generation of thin-film deposition technology. The Principal Mechanical Engineer will be responsible for the design and implementation of advanced R&D equipment and complex machinery. This role requires strong technical expertise, procedural discipline, and the ability to collaborate across engineering and technology functions to ensure safe, reliable, and high-performance equipment. If you enjoy working on complex design problems, mentoring others, and solving problems in a collaborative, fast-paced environment, this is your opportunity to make an impact.

What you'll do

• Lead the design and implementation of advanced R&D equipment for thin film processing, including ownership of key mechanical modules and sub-systems
• Define system level requirements and drive innovative design concepts to meet these requirements
• Lead design reviews for overall mechanical system and key mechanical subsystems
• Generate and maintain interfaces with other engineering subsystems
• Report on and be accountable for project progress to stakeholders
• Work effectively within a multi-disciplinary team of top scientists and engineers
• Mentor engineering staff for effectiveness and delivery of on-time & in-spec outcomes
• Get things done: drive projects, consistently deliver, act with speed

What we're looking for

• Master's degree in Mechanical Engineering or related field (or equivalent industrial experience)
• 15+ years of experience with at least 7 years of experience working as a principal mechanical design engineer or engineering team lead in a relevant context: design and implementation of R&D systems and manufacturing equipment
• Ability to conceive of novel solutions for complex engineering systems in challenging environments
• Expertise with 3D modeling; preferred experience with SolidWorks and NX
• Experience with COMSOL, ANSYS or other FEA tools
• Ability to select and qualify vendors for components or subsystems
• Demonstrated ability to lead in either direct or matrix structures
• Strong verbal and written communication skills and a dedication to high-quality documentation

Bonus points for

• Ph.D. in Mechanical Engineering or related field (or equivalent industrial experience)
• Prior success building first-of-kind or experimental tools for material science or semiconductor R&D
• Familiarity in applying Semi-S8, ASME, ACI, ASTM, and other mechanical standards to design solutions
• Experience with the operation of equipment in a manufacturing environment

Must-have Requirements

• Ability to occasionally lift up to 50 lbs
• Perform activities such as stooping, climbing, standing, or sitting for extended periods of time
• Dedication to safety to mitigate industrial hazards that may include heat, cold, noise, fumes, strong magnets, lead (Pb), high voltage, and cryogenics
• Willingness to travel or work required nights/weekends/on-call occasionally

$150,000 - $225,000 a year

Salary range for this full-time position + equity + benefits. The actual salary will depend on level, location, qualifications, and experience. The range displayed on each job posting reflects new hire salaries for the position across all US locations. Benefits include:

• Competitive compensation with equity
• 12.5 Company-wide Holidays
• Flexible vacation days
• 10 sick days
• Generous parental leave policy
• Health, dental, and vision insurance
• 401(k) with employer matching
• Professional growth opportunities
• Team-building activities

At CFS, we excel in fast-paced environments, driven by our values of integrity, execution, impact, and self-critique. As we grow, we're eager to bring on mission-driven folks who offer diverse perspectives and fresh ways to tackle challenges.

We value diversity deeply and are proud to be an equal opportunity employer by choice. We consider all qualified applicants equally, regardless of race, color, national origin, ancestry, citizenship status, protected veteran status, religion, physical or mental disability, marital status, sex, sexual orientation, gender identity or expression, age, or any other basis protected by law.

This role requires compliance with U.S. laws concerning the export of controlled or protected technologies or information (collectively, "Export Control Laws"). Any offer of employment will be contingent on the need for compliance with such Export Control Laws.