(7/8) The complete industrial designer – Hardware UX

If you landed here directly, check out the first six posts of this series, The complete industrial designer:

Stage 1: Research & observation
Stage 2: Sketching
Stage 3: Form & proportion
Stage 4: CMF
Stage 5: CAD & surfacing
Stage 6: Prototyping & model-making

We're on the last leg of the project and before you give the project to your design engineering counterpart, here's an important aspect that you should cover now. Hardware user experience or Hardware UX (HUX).

As a matter of fact, you have been covering HUX in bits and pieces through the previous stages too but this is the time we do it methodically.

One of the clear bottles I have comes with a button style flip-lid which opens 180°, and it has a shaker accessory too. I use the white one as my default at-home water bottle and the white model as my daily protein shaker. But my wife doesn't use it. She loves the bottle, by the way. She loves the quality, some of the features too, but she doesn't like how the rubber cap to seal the spout touches her nose when she tilts the bottle to drink water.

The lid fits tight and confident but once it's been closed tight it takes real effort to open. In a kitchen, where your hands could be wet and the cap is smooth matte, everyone else here just avoids the bottle. They use other bottles or ask me to open it before I leave for work.

That's a hardware UX failure, and the annoying part is that it was completely specifiable just like any other part of the bottle.

Hardware UX for this bottle

We want the bottle to feel solid, premium, and satisfying to use. Now if you break these feelings into something tactical, we're talking about specific things.

How does the button feel is actually button force that's firm enough that things in the bag can't press it, but light enough for a thumb which is already holding a kilo of water. This feeling is button force of 4 to 6 newtons.

Continuing with the button, there's how much you want to press to open the lid. The button travel could be 2 to 3mm, with a hard end to it because without a defined end, the travel feels broken. At the end of the button travel is the great click feel. The click is a feel and not a sound.

You can measure the force at the peak of the press and the force right after it drops by ~50% which gives it a proper snap. A lower drop here would feel mushy and not satisfying. This reminded me of car doors here. That thunk is seal compression, latch geometry and panel damping until the door made that sound.

Similarly, think about cap swing. Cap swing is how far the cap opens and how does it stay there. It shouldn't fall on your face while you're drinking. The method could be a bit of detent at the open position or spring-based hinge, or 10° of more travel.

Then there's seal compression, the right flow of water which will make the spout roughly 20 to 25mm wide with a vent.

One-thumb reach is an important UX to solve for. Hold the bottle at its natural balance point. The button has to sit under the thumb without re-gripping. On a litre that balance point is high, which pushes the button up onto the wall of the cap.

Now there are numerous use cases you should consider closely.

When the lid is closed but not latched, can the user tell but just looking? A button that doesn't sit flush unless it's locked or a coloured surface that only shows when it's open.

When the bottle is open and someone is drinking from it one-handed and walking, is the cap swung back and looking flimsy or is it rigid and touching the back of your hand and the profiles of the cap cannot be ribs-like.

How's one filling the bottle under a tap? How much clearance is required? How often the cap needs to be fully off for washing? How easy or difficult should the threads be? When the parts of the bottle are kept for drying, will the intended parts stand inverted so it dries completely to not let smell hold? Do the seals come out without a tool? If a seal needs fingernail dug into a groove, user's won't take it out and it'll grow a black ring. And if the seal doesn't go back right, they'll not seat properly and may leak.

And all the things we covered in the earlier stages of design - how's it carrying with the loop, how's it swinging, even if it's hitting a doorframe, or in the bag, on the side of the bag, or kept next to a laptop, half empty in a meeting where it might get noticed the most.

The button and latch. A crisp snap reads engineered and a soft plastic clack reads cheap. The difference comes from that force drop, plus how much air gets trapped behind the button.

The uses cases don't stop here. There are a lot more a bottle absorbs through the day, through the week, through seasons over years.

How you know it's all covered

Once you write the use cases from above, mark these as annotations on the sketches and prototypes you've done already. If you've done the previous stages properly, the above should just be a checklist. Since you're focusing on just the UX for this bit, it'll help you focus more. The ones you can't put in earlier explorations are the ones you haven't handled yet.

You'd now also be able to assign a specific number for each of the UX markers. Be it for hinge, spring, latch, seal, or such.

Everything you do here will lead to the first ninety seconds when a user takes the bottle out of the box and operates without any instruction and falls in love with the bottle.

Deliverable

Couple of simple documents really.

The interaction specification document. Make a table with five columns. The interaction, the number with its range, the unit of measurement, how to measure, and the trade-off.

Keep a clear document for user states. What the user is doing, what the product has to do, and whether the current design handles it. Colour code the ones product already does or needs to be fixed.

A test plan for the bottle. It should have all the moving parts, its cycle target, the test method, and the pass criteria.