Product Design Engineer Interview Questions UK: 8 Real Questions and What Interviewers Want

Applying for a Product Design Engineer job in the UK? Here is what you are likely to be asked. These questions come from our Product Design Engineer question bank of 16 questions, written for UK employers at mid-level level.

Eight Product Design Engineer interview questions, and what the interviewer is thinking

1. Walk me through how you take a product from concept to production release, and where you personally add the most value.

Why they ask: They want to see you understand the full product development lifecycle, not just CAD modelling.

2. How do you design a plastic injection moulded part for manufacture? What features do you look out for?

Why they ask: Injection moulding is core to most product design roles and poor design choices become expensive tooling problems.

3. How do you choose a material for a new component, and what factors do you weigh up?

Why they ask: Material selection shows engineering judgement across performance, cost, process and regulation.

4. What is a tolerance stack-up, and how would you carry one out on an assembly?

Why they ask: Tolerance analysis prevents assembly failures and is a core product design skill.

5. Which CAD and simulation tools have you used, and how do you decide when FEA is worth doing?

Why they ask: They are checking tool proficiency and whether you apply analysis proportionately.

6. Your tooling supplier says a feature on your moulded part will cause sink marks and wants a design change, but the customer has already approved the design. What do you do?

Why they ask: They are testing how you balance supplier feedback, customer commitments and cost.

7. Tell me about a time a design you were responsible for failed testing or had a problem in the field. What did you do?

Why they ask: They want evidence of accountability, root cause skills and learning.

8. Why do you want to work as a product design engineer, and what parts of the role do you enjoy most?

Why they ask: They want to gauge genuine motivation and understanding of the role.

A sample answer to question 1

Walk me through how you take a product from concept to production release, and where you personally add the most value.

I normally work in stage-gate phases. It starts with the requirements: user needs, target cost, standards and manufacturing volumes, captured in a product design specification. I then generate concepts through sketching and quick CAD, screen them against the spec with a weighted decision matrix, and prototype the best two or three, often using SLS or FDM printing so we learn cheaply. Detailed design in SolidWorks follows, with DFMA reviews alongside the tooling supplier, tolerance stack-ups, and FEA on anything load-bearing. Then comes validation testing, first-off tool samples, and a PPAP-style sign-off before release through the PDM system with a proper ECN. Where I add most value is the middle: translating a vague brief into a robust, manufacturable design, and flagging cost or tolerance issues early, because a change at tooling stage costs roughly ten times what it does on screen. I also keep a design history so decisions can be traced later.

Common mistake to avoid: Describing only CAD work; skipping validation and manufacturing handover

Want the rest?

Full model answers, key points and common mistakes for all 16 questions are on the Product Design Engineer interview questions page. The first five are free, no sign-up needed.