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Principal Mechanical Engineer Vacuum

Commonwealth Fusion Systems

Job Location:

Milpitas, CA - USA

Yearly Salary: $ 150000 - 225000

Posted: 22 August 2026 (20 hours ago)

Application Deadline: 19 November 2026

Vacancies: 1 Vacancy

Job Summary

About Commonwealth Fusion Systems:

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

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

Were in the best position to make it happen. Since 2018 weve raised $4 billion of capital making us the largest and leading fusion company in the world.

Now were looking for more thinkers doers builders and makers to join us. People wholl bring new perspectives solve tough problems and thrive as part of a team.

If thats you and this role fits we want to hear from you.

Join the power movement as a Principal Mechanical Engineer

Were looking for a Principal Mechanical Engineer to join our R&D and equipment design team to help build the next generation equipment. You will be responsible for the end-to-end design integration and implementation of advanced thermal vacuum equipment and R&D machinery.

This role requires you to be a technical expert who can drive innovative architecture while maintaining the procedural discipline necessary for high-performance hardware. If you enjoy solving complex thermal-mechanical problems in vacuum environments and mentoring others in a collaborative fast-paced setting this is your opportunity to make an impact.

What youll do:

Lead System Design: Drive the design integration and validation of advanced R&D processing equipment
Define Requirements: Establish system-level requirements and innovative design concepts that directly correlate mechanical precision to product quality
Standardize Best Practices: Implement and maintain engineering workflows and best practices using semiconductor standards as your guide
Lead Design Reviews: Conduct rigorous reviews for overall mechanical systems and sub-systems emphasizing manufacturability (DFx) and best practices for mechanical design
Collaborate & Interface: Generate and maintain critical interfaces with cross-functional teams including scientists vacuum specialists and electrical engineers
Project Accountability: Report on project milestones to stakeholders ensuring delivery of on-time and in-spec outcomes
Mentor Talent: Coach engineering staff on technical delivery procedural discipline and professional development
Get Things Done: Act with speed to drive projects from concept through assembly testing and implementation

What were looking for:

Education: Masters degree in Mechanical Engineering or a related field (or equivalent industrial experience)
Experience: 15 years of experience in the design and implementation of complex R&D systems or semiconductor manufacturing equipment
Thermal & Structural Expertise: Proven capability in high-temperature structural design and complex thermal management within vacuum environments
Vacuum System Proficiency: Deep understanding of vacuum architecture including material outgassing seal integrity and pump-down optimization
Software Mastery: Expertise in 3D modeling (SolidWorks and/or NX) and FEA/Thermal simulation tools (COMSOL ANSYS)
Hands-on Capability: Ability to bridge the gap between design and the shop floor including experience with manual/CNC machining prototyping and hardware troubleshooting
Vendor Management: Experience selecting and qualifying global vendors for specialized components or custom sub-systems
Leadership: Demonstrated ability to lead effectively in both direct and matrixed organizational structures

Bonus points for:

R2R Expertise: Experience designing or integrating roll-to-roll (R2R) systems for material processing
Semiconductor Background: Prior success building first-of-kind or experimental tools for semiconductor R&D or thin-film deposition
Standards Knowledge: Familiarity with SEMI ASME ASTM and other industry-standard mechanical codes
Motion Control: Experience designing precision motion and motor-controlled systems within challenging environments

Must-have requirements:

Ability to lift up to 25 lbs occasionally
Perform activities such as stooping climbing standing sitting for extended periods of time
Willingness to travel or work required nights/weekends/on-call occasionally
Dedication to safety to mitigate industrial hazards that may include heat cold noise fumes strong magnets lead (Pb) high voltage high current pressure systems and cryogenics

$150000 - $225000 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

13 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

#LI-Onsite

At CFS we excel in fast-paced environments driven by our values of integrity execution impact and self-critique. As we grow were 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.

Required Experience:

Staff IC

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