Mechanical Engineer C5R San Francisco, CA Job Details Full-time $135,000 - $200,000 a year 3 hours ago Benefits Relocation assistance Health insurance Paid time off Referral program Qualifications Rapid prototyping Motion controls Schematics 3D printing Debugging Full Job Description C5R builds research facilities for frontier models: physical environments where models can design experiments, operate instruments, learn from results, and be evaluated on real scientific work. We build facilities end to end, bringing together the physical site, instruments, robotics, software, and operations. By working closely with model developers, we continuously produce the data and physical feedback their models need for pretraining, lab-in-the-loop post-training, and evaluation. The role We are hiring a mechanical engineer to design, build, and iterate on the physical systems that make an automated research facility work. Our facilities are built from smart benches, robot arms, mobile carriages, custom fixtures, and reverse-engineered scientific instruments — all of which have to work reliably, repeatably, and around the clock. You will own the mechanical design that holds it together, and you will be on the floor when it doesn't. You will work across the mechanical stack: CAD, fixture and tooling design, structures, enclosures, thermal, tolerance stack-ups, and fabrication.

Examples of work might include:

Designing a gripper fingertip or plate fixture that survives ten thousand pick cycles without drifting out of calibration tolerance. Building the mechanical interface between a robot arm and a scientific instrument that was never meant to be automated. Designing enclosures, mounts, and cable management for benches packed with arms, cameras, power distribution, and networking. Running tolerance and structural analysis on a bench frame, then machining or printing the part yourself the same week to prove it out. Collaborating with controls and ML engineers to understand why a robot failed, then concretely improving the fixture, mount, or mechanism to fix it. Who we're looking for Strong practical mechanical engineering experience. You should have built and debugged real hardware, not only models. CAD fluency (Onshape, Solidworks, or equivalent) with real design intent — parts that get made, not parts that look good in a render.

Hands-on fabrication experience:

3D printing, machining, laser cutting, sheet metal, or other rapid prototyping workflows. Good fundamentals in tolerancing, materials, fastening, and mechanism design. Comfort at the boundary with other disciplines — you should be able to read a schematic, reason about a motor's torque curve, and talk to a controls engineer without a translator. Nice to have Precision motion, kinematic mounts, or repeatable fixturing. DFM/DFA and experience taking a design from one-off to a small production run.

Electromechanical packaging:

connectors, cable routing, thermal management, interlocks. Experience with lab automation or scientific equipment. Compensation & terms We are open to full-time roles and temporary stints of at least 3 months. Compensation depends on experience and structure. This role is on-site in San Francisco only.

Pay:

$135,000.00 - $200,000.00 per year

Benefits:

Health insurance Paid time off Referral program Relocation assistance

Work Location:

In person