How to Interview a Product Design Engineer

As a former Product Design Engineer, I’m often asked for advice on how to hire Product Designers (PDs) or mechanical engineers (MEs). In small teams, this is an especially tricky hire because the PD is never “just a PD” – they are often a combination of PD, quality engineer, and engineering program manager (EPM) who will own all the parts of the hardware process. Luckily, many experienced PDs have had broad exposure to the hardware development process, and can usually cover these other roles too, as long as the product design isn’t too complex.

Stage 1: Job Description

Most PDs will oversee the following, which you’ll want to make sure you cover in your job description:

• Owning the end-to-end mechanical design
• Understanding and defining the product requirements
• Creating robust designs that balance performance, manufacturability, and cost

You’ll also want to reference the specific challenges your product requirements will have in order to attract candidates who are excited about the challenges you are solving (and hopefully have some relevant experience). Some challenges that are considered exciting for PDs might be:

• Aggressive waterproofing requirements
• Working with “cool materials” such as ceramics or organics
• Challenging mechanisms designs (if there are moving parts)
• Designing new manufacturing processes

If it’s applicable to your product priorities, it may also be worth mentioning that the PD will be a champion for product quality. Even if you have a dedicated quality engineer — or a quality team — your PD will be in a key position to understand and drive the aspects of quality that matter for your product.

What about experience required? Every PD was a new graduate once, and some of the best ones I know didn’t even study mechanical engineering. I went to graduate school and I don’t feel like I really learned how to be an engineer until I was sitting on the line figuring out how to retool a design to make it more manufacturable. In my personal experience, book learning didn’t prepare me for the education I got in my early years doing high volume consumer electronics with a lot of responsibility. If you’re a small team looking for your first PD, find the most experienced one that you can. If your team already has an experienced PD, hiring someone with less experience can be a great growth opportunity for the new hire and your existing teammate. If you’re a large organization, hiring new graduates gives you first dibs on the best new talent.

Stage 2: Technical Depth and Breadth

The basic goal for the first conversation is to understand the candidate’s depth and breadth. Does the candidate “think like an engineer”?

(1) Can the candidate describe the process behind how something is made?

I remember when I was interviewing to be a PD at Apple, and I was handed the double-shot plastic face of an iPod classic and asked where the gates were in the tools used to make it. It was the first double-shot part that I had ever seen, and even though I had a little experience with injection molding, I couldn’t see any gate marks. It was a trick question: the part was gated in the scroll wheel area, and the evidence was removed in a post-process CNC step. As a candidate, my mind was blown; I wanted to solve problems in clever ways like that. I’m not advocating for trick questions in your process, but having a candidate talk you through their thought process can give you a sense of their background and creativity.

(2) Can the candidate defend a material selection choice for a mechanical component?

For example, what material should a snap be made out of, and why? Hint: Both sides of a snap interface should never be aluminum. You’ll also want to listen for words like flexibility, fatigue, lubriciousness. These are all considerations.

New graduates will probably not do well on these questions because most university students have only experienced 6061-T6 aluminum, 304 stainless steel, and maybe some plastics like Delrin and acrylic. But if a new graduate remembers the grade of materials they have worked with, and can come up with an exhaustive list of things to test and specifications to look up – this can indicate a thought process that is ready to absorb new learning on the job.

(3) How many samples does the candidate think should be tested in reliability testing and why is that the right amount?

Stellar answers to this line of questioning will consider the use-case scenarios and demonstrate a basic understanding of manufacturing variability and statistics. This is a very revealing question, the why being more important than the number. Except in extreme situations, any answer that is less than five or more than 100 is probably wrong.

PD’s need to have to have a certain amount of grit – spending days on manufacturing lines in China solving hard problem takes a certain kind of character. So in addition to understanding technical depth and breadth, I suggest detailed lines of questioning about a really gnarly engineering challenge he or she had to solve will give you a lot of insight into how the candidate breaks down problems and digs into tough situations.

Stage 3: Design Skills

By now you’ve already determined that your candidate looks like a potential fit based upon their background experience – now it’s time to see how that candidate applies their experience and intuition to solving design problems. This part of the interview can be particularly challenging if you are hiring your first PD, because you need a PD to help to design and grade the test.

You’ll want to make a design problem that is deceptively simple, but due to trade-offs that must be made, is actually quite difficult. As with all interview questions, you want to create a spread between candidates – and that difficulty will do that. What determines pass or fail in the interview isn’t whether or not the design will “work”, but rather whether the candidate took into consideration all the facets and trade-offs and made good decisions. Here’s several examples:

• Apple iPod / Watch PD famously uses a battery door design challenge, so in addition to doing it myself back in 2009, I’ve also seen many 10s of them during my time at Apple. The prompt is to design a battery door that uses a push-push mechanism. What makes this difficult and creates a spread among candidates is really in how he or she approaches and defends the resulting design. A candidate who considers material selection, manufacturability, assembly complexity, part cost, system and part reliability (including test plan and quantities), and (because it’s Apple) cosmetics is going to do well, even if it’s unclear that the design will work.
• Pick an important sub-system of your product that your new hire will need to get right – such as a water-sealed enclosure. There’s many ways to solve this problem, but you’ll want to look at the details. Did the candidate consider cost, reworkability, manufacturability, design complexity, materials, reliability testing, and cosmetics? For example, if the candidate used an o-ring gasket, is the groove designed such that added pressure actually makes the seal better? Is there even compression all of the way around?
• Or pick a challenge that is explicitly a trade-off challenge: A processor chip that needs to be EMI shielded with a solution that also sinks heat. Have the candidate develop two heat sink / EMI solutions that take up the minimum amount of board space around the processor and also minimize custom part count, cost, complexity, and time to assemble on the line – and then develop criteria to select the best one. By creating two solutions and requiring the candidate to choose the best one, you can get insight into how he or she will make important trade-offs in his or her daily work at your company.

Stage 4: Interpersonal and Team Skills

While it may seem like a PD should be spending most of his or her day doing CAD, doing failure analysis, or watching parts going down the line (all pretty solitary activities) – the role is often incredibly cross-functional, and interpersonal skills like communication and collaboration are just as important.

You’ll want to understand whether your candidate will work well with your existing team. In order to do this at Instrumental, all roles have a “team exercise” portion where we seriously work together on a made up problem. If you are building in China, you’ll want to consider the candidate’s experience working with remote teams and communicating with non-native speakers and writers of English.

You’ll want to see you candidate defend his or her ideas. One easy way to do this is to have him or her present the design test to a broader panel of engineers and face some questioning. This can take on whatever culture your company has and whatever level of intensity is required for success in the role. At Instrumental, this is a friendly discussion where the candidate takes the lead and panelists ask thoughtful questions along the way to probe depth of understanding. At Apple, the panel was much more pointed and perhaps at times could be considered a bit brutal (by design), because withstanding intense scrutiny was what the team believed was required for success in the role.

If the role is going to be multi-faceted, you’ll want to test instincts around quality, program management, general program organization, etc.

I also always want to ask a PD about Geometric Dimensioning and Tolerancing (GD&T). One might think something as boring as GD&T wouldn’t create controversy, but depending on your industry, it can. The key reason is because Chinese manufacturers don’t follow it. It doesn’t matter if you have specified the flatness of a surface or a profile callout on a drawing using formal GD&T if your vendor won’t (or cannot) measure it. If that’s an environment that you work in, you’ll want to get a sense for the candidate’s intuition about what really matters to get the desired outcome. In consumer electronics, this usually means using “simple dimensions” (which is a term of art). I usually dig into issues around GD&T by asking a series of questions around defining datums for a complex part. My go-to part is an iPod home button: how do you define the datums to reduce the gap and offset between the button and the glass, and the tilt of the icon with respect to the glass? I usually draw a few views of the button on the whiteboard and have the candidate explain his or her thought process. This question is not easy, but the decisions your PD makes when making drawings will dictate how tools are made, which dimensions are actually being controlled, and ultimately the final fit and finish of your product.

Final Note: Specialized Backgrounds

Specialized backgrounds give candidates specialized experience. Think about what you need for your product and consider targeting candidates from specific industries. For example, candidates from the medical device industry will be trained to design things to be robust and to conduct extensive sub-component testing to make sure the first build is good (because medical devices usually only get two builds). Whereas, engineers from a BigCo consumer electronics background will have been trained that schedule is king, often preferring to kick off many backup versions in parallel to each other. Candidates from startups will be used to working with a budget and fewer resources to do experiments, and so may be scrappier. All of these candidates can bring different kinds of experience to your team, so you may consider sourcing directly from a pool of talent most likely to have the skills you need.