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- Tasks: Lead the design and testing of innovative low-carbon technologies in a collaborative engineering team.
- Company: Cocoon is revolutionising construction with greener steel and cleaner cement solutions.
- Benefits: Enjoy competitive salary, stock options, and flexible working arrangements.
- Why this job: Join us to make a real impact on climate change while developing cutting-edge engineering solutions.
- Qualifications: 5+ years in mechanical systems, strong CAD skills, and a passion for problem-solving required.
- Other info: Be part of a diverse team committed to sustainability and innovation.
The predicted salary is between 46000 - 65000 £ per year.
Cocoon is driving the circular economy between steel and cement by turning steel slag into a low‐carbon cement substitute.
We\’re backed by leading climate and hardware tech investors, including Gigascale, Wireframe, and Celsius Industries. In under two years, we\’ve gone from concept to deploying our breakthrough technology at one of the largest steel producers in the US. We\’re doubling the team in 2026 to tackle the next wave of technical challenges as we scale towards our first permanent production plant.
As part of Cocoon, you\’ll own end‐to‐end development and validation of our mechanical systems, working alongside engineers, scientists, researchers, and technicians to develop and scale our technology. The role will be challenging; design, build, and validate new systems, giving you the chance to materially cut emissions from two of the most carbon‐intensive industries in the world.
The RoleWe\’re looking for a Mechanical Engineer to lead the design, build, and validation of mechanical systems and test rigs that underpin Cocoon\’s next‐generation slag activation technology. You\’ll work closely with engineers, material scientists, researchers, and technicians to mature R&D outputs into robust, scalable system designs.
This role spans experimental design, detailed mechanical engineering, supplier coordination, and hands‐on testing in the UK and overseas. You\’ll own end‐to‐end development and validation workstreams — from concept through commissioning — and play a key role in scaling our technology toward our first industrial plant.
ResponsibilitiesMechanical Design & Development
Lead mechanical engineering for R&D workstreams, owning delivery from concept to validation.
Design experiments, methods, and associated test rigs to validate and advance core technologies.
Develop mechanical designs for hydraulic systems, industrial instrumentation, and bulk material handling systems.
Use simulation, first principles, and engineering judgement to validate designs.
Build, Testing & Validation
Source components and manage subcontractors for delivering designs and test rigs.
Manage the build and delivery of test rigs; create assembly documentation and direct manufacturing and installation activities.
Lead validation and testing activities in the UK and overseas, from requirements definition through commissioning and testing.
Create documentation for validation and compliance activities (DFMEA, risk registers, operating instructions, test reports).
Support testing campaigns at Cocoon\’s London R&D facility, UK pilot facilities, and US partner sites.
Collaborate closely with the process engineering team to translate R&D outputs into system specifications for industrial deployment.
Provide technical direction to engineers, technicians, and suppliers.
Contribute to scaling technologies from R&D toward pilot and industrial deployment.
Travel extensively during test campaigns to support installation, commissioning, and testing activities.
You\’ll Succeed In This Role If You…
Hold a Master\’s degree in engineering and have at least two years of industry experience in mechanical, hydraulic, or electromechanical systems.
Have experience defining experiments, designing test rigs, and managing validation testing.
Are comfortable owning complete development and validation workstreams in a fast‐moving environment.
Bring strong problem‐solving skills and enjoy hands‐on troubleshooting and prototype building.
Communicate clearly with technical and non‐technical stakeholders and can lead work delivered by others.
Knowledge of industrial automation, instrumentation, or PLCs.
Understanding of process engineering (material handling, heat transfer, unit operations).
Experience with high‐temperature fluid handling or metallurgical systems.
Experience scaling technologies from TRL 4/5 to TRL 8/9.
Background in steelmaking or related heavy industrial environments.
What We Offer
A hands‐on engineering role at the centre of Cocoon\’s scale‐up journey.
Ownership of real hardware development and validation work.
Close collaboration with a multidisciplinary, mission‐driven team.
Competitive salary, stock options, and flexibility where possible.
If you\’re excited about designing, building, and validating first‐of‐a‐kind mechanical systems — and helping decarbonise heavy industry — we\’d love to hear from you.
Referrals increase your chances of interviewing at Cocoon by 2x.
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Mechanical Engineer employer: Cocoon
Contact Detail:
Cocoon Recruiting Team
StudySmarter Expert Advice 🤫
We think this is how you could land Mechanical Engineer
✨Tip Number 1
Familiarise yourself with Cocoon's mission and values. Understanding their commitment to decarbonising the steel and cement industries will help you align your passion and expertise with their goals during conversations.
✨Tip Number 2
Network with current employees or industry professionals who have experience in mechanical engineering within sustainable practices. This can provide you with insider knowledge about the company culture and expectations.
✨Tip Number 3
Prepare to discuss specific projects where you've led product lifecycles or implemented innovative solutions. Highlighting your hands-on experience with prototypes and troubleshooting will demonstrate your practical problem-solving skills.
✨Tip Number 4
Be ready to showcase your proficiency in CAD software, especially Solidworks or Catia 3Dx. Consider preparing a portfolio of your designs or simulations that illustrate your capabilities in mechanical systems.
We think you need these skills to ace Mechanical Engineer
Some tips for your application 🫡
Tailor Your CV: Make sure your CV highlights relevant experience in mechanical, hydraulic, or electromechanical systems. Emphasise your proficiency in CAD software and any experience with product lifecycle management.
Craft a Compelling Cover Letter: In your cover letter, express your passion for sustainability and how your skills align with Cocoon's mission to decarbonise the construction industry. Mention specific projects or experiences that demonstrate your problem-solving abilities.
Showcase Technical Skills: Include specific examples of your technical skills, such as FEA, mechanism design, and GD&T standards. Highlight any experience you have with PLC programming or industrial automation, as these are valuable for the role.
Prepare for Interviews: If invited for an interview, be ready to discuss your previous projects in detail. Prepare to explain how you approach problem-solving and your experience in leading projects, as well as your adaptability in a dynamic startup environment.
How to prepare for a job interview at Cocoon
✨Showcase Your Problem-Solving Skills
Cocoon is looking for practical problem solvers, so be prepared to discuss specific examples of how you've tackled complex engineering challenges in the past. Highlight your adaptability and how you thrive in dynamic environments.
✨Demonstrate Your Technical Proficiency
Make sure to showcase your experience with CAD software like Solidworks or Catia 3Dx. Be ready to discuss your familiarity with FEA, mechanism design, and how you've applied these skills in previous projects.
✨Prepare for Hands-On Discussions
Since the role involves being hands-on with troubleshooting and building prototypes, be ready to talk about your practical experiences. Share any relevant projects where you had to lead testing campaigns or manage product lifecycles.
✨Communicate Effectively
Strong communication skills are essential for this role. Practice explaining complex technical concepts in simple terms, as you'll need to convey ideas to both technical and non-technical audiences. This will demonstrate your ability to collaborate effectively within a team.
