My Five Principles for Great Physical Product Design

When starting a physical product business from scratch, as I’m doing with Parallel right now, it’s given me time to reflect on the types of products I want to design, manufacture and sell. The rules for something to constitute “good design” in my book are clear and unchanging. Physical product design is a creative endeavour that can operate without rules or guidelines if selling in very small numbers. These principles are conducive to creating and selling products in the 100s & 1000s. They allow me to grade my own work as a product designer, but also give me confidence in the commercial element of the designs themselves. If done correctly, products that are designed by these principles should be:

  • Economical to produce
  • Easy to maintain & repair
  • Foster long term working relationships with your suppliers
  • Appreciated for their aesthetics
  • Handed down to future generations
  • Reliably achieve their intended function for years to come
  • Emphasise your design decisions to the customer, without further explanation

Principle 1: The design respects the end manufacturing process.

When you have an idea for a product, at the beginning it’s tempting to totally disregard how this thing might be made. At the start, you’re just trying to get the thing to work so you shouldn’t worry about things like draft angles and uniform wall thicknesses. At Dyson, if you were in the very early stage department, you were encouraged to never thing about these things. The thinking was, get it to work first, then we’ll worry about how we’re going to make it in high volumes later. It was my job to take the working designs, then turn them into something that could be made millions of times. Nowadays, I prefer starting at the manufacturing process and working backwards. I absolutely love manufacturing and I guess my obsession with “How it’s Made” programme has stuck with me into adult life. When visiting factories in Shenzhen (in reality it was probably closer to Dongguan — Shenzhen is so built up there aren’t many factories near the centre anymore), there is an endless amount of inspiration from seeing how these factories operate. When you know how the factories like to work, if you present a design to them that is in line with this, your whole experience will be 100 times smoother. Your part price will be lower, your failure rate will be lower and the quality of the product will be higher, win-win-win.

A precision centre finder from Rutlands, using CNC’d Anodised Aluminium

When you’re designing for a given manufacturing technique there will be rules you need to follow to make the design as efficient as possible to produce. With CNC, as it’s a subtractive process, you want to start with the raw piece of material first — is it a billet, a flat piece, or a rod? The price of the part will reflect a few variables:

  1. The time it takes to machine the part, similarly, the number of operations it requires. How many features does your part have — can you simplify it?
  2. Can the part be machined from one side only? If so it will be cheaper, if not they’ll have to flip it to machine the underside which takes a bit of time, or means they’ll need to use a better machine that can flip automatically, which also increases the price.
  3. What’s the smallest bit size the machinist will need to use? If it’s a small bit, then they will need to charge you for every bit they break, which happens a lot. This slows down production too if the smallest bit is something like a 2mm diameter you should be ok. You can tell your smallest bit size by the smallest inside radius your part has.
  4. The raw cost of the material. The most common machining metals and approximate costs are Aluminium 6061 ($4 per kg), Stainless steel ($5/kg), Brass ($6.9/kg), Copper ($8.4/kg) and Titanium ($ 16.9/kg). Prices as of 13/01/21 courtesy Yi Xin, Dongguan.
  5. The finishing processes required, sandblasting, anodising, blackening etc all add processes and cost.

A part that’s been designed with these rules in mind will show in its relatively low cost to produce and also it’s aesthetics.

A custom Titanium, Sand Blasted Swiss Army Knife made using CNC.

Each process will have its own limitations and design guidelines. If you want to read more about all the different processes out there, I recommend the book Making It by Chris Lefteri. The point here is that when a physical object has been designed with a particular process in mind, these details add to the look and feel of the finished product. The way something is made should be celebrated, rather than painted over.

A simple yet beautiful cast-iron casserole dish. It has a natural finish with imperfections caused by the sand casting process.

Principle 2: Eliminate Unnecessary Details

The shoe company Feit specialises in working with master craftspeople and creates the most simple style of shoes possible. It turns out, to make something look simple, like using only one piece of leather for an entire top section of the shoe, is incredibly difficult. The result is a product without any more stitches than it requires, with a minimalist, clean look.

Feit Desert Boots, made with a single formed piece of suede, stitched onto its sole and heel.
Another example of simple, honest construction techniques.

This principle is a tricky one because it sometimes goes against principle 1. Forcing a design to look simple and minimalist, whilst using a manufacturing technique that doesn't allow for it can end badly. Trying to force a perfect design from imperfect manufacturing process treads the line between perfectionism and self-indulgence. Take Hartmut Esslinger, when designing the famous failed NeXt computer using die-casting:

The ambition here is to fully understand the manufacturing process and use it to create the most simple forms possible, that can be made in a straight forward fashion, with consistently high-quality results.

But what about progress? What if we want to do something that can’t be done? In my previous role creating injection moulded parts for Dyson, truthfully I didn’t appreciate the manufacturing technique as much as I should have in that position, even though I was supposed to be training other engineers on the subject :/ I would submit parts for tooling that required about 20 different movements, with collapsible cores and a long list of weird geometries. All of these equate to more expensive parts and tools. Instead of being pushed back, our tooling engineer was so used to designs this complex he said: “it’s a tricky one, but they’ll manage.” My point here is that settling with complicated designs because a supplier is capable of doing it can actually be lazy, rather than progressive. It boils down to learning the rules of the manufacturing process, designing within those guidelines and making the design as simple as possible. If done right, the aesthetics will be better and the design will be cheaper and easier to produce too, win-win.

Principle 3: The design works perfectly, even in our imperfect world.

Do you know how apple get to that “it just works” moment with their products? It boils down to thousands upon thousands of hours of engineering analysis and testing.

iThe apple watch strap, simple but effective.

Even something as simple as the apple watch strap, with its pin & hole style friction fit, has been designed to be made as such scale, and at every point be consistently hitting their quality standards. Not everyone can spend so much time on quality control and design as Apple can, but there are a few ways to get to a dependable quality with some good design decisions. Everyone wants high yield (the number of products that can be made according to specification in a particular amount of time, usually a day) and high-quality products. One way to do this is to set a very high standard of quality and check them all individually. This way you can only release products that hit your high standard. This will result in your products being high quality, yes, but your manufacturing yield and therefore price you pay, your relationship with the supplier and amount of time dedicated to quality control goes quite quickly out of control. The other way of doing it is to design your products to cope with even lower tier factories with poor quality control practices, this can be achieved with a choice of materials and clever approach to tolerance. Within the manufacturing industry, this is referred to as capability index. In basic terms, it means how repeatable their processes are and how consistently your parts may be made. From my experience of dealing with small numbers of parts and lower-tier suppliers, technical terms like capability index are rarely mentioned.

In short, if your design still works with perfectly with not so perfect parts, you’ve considered the possible variation you might expect from your suppliers then you’ve hit the nail on the head. I heard that on the first assembly line for the DC01, Dyson’s first vacuum cleaner, the British engineers had thousands of oddly shaped parts and would walk down the line trying each one until they found one that fit, and the entire vacuum cleaner was made this way. Nowadays, the Dyson engineers are all taught to design their products to work, even with inaccurately produced parts.

If your design still works through the extremes of inaccurate manufacturing techniques, then you’ve cracked it.

Principle 4: The product ages gracefully.

If you can design a product that looks better with use, then you’re on the money. This is the sort of product that will be cherished, used well, and hopefully handed down to the next generation. With more products made with this ethos, there will be less need to buy new things, meaning consumption goes down overall. Using the same bottle opener your entire life is a lot cooler than getting the next plastic gadget that comes out that makes it 10 times more efficient to open bottles.

A vintage brass bodied Leica camera with its years of use showing through, still looking brilliant.

My great grandfather on my mum’s side was a tailor, and he used Wilkinson sword scissors to cut the fabrics and cloth. The scissors themselves are in excellent condition and have been clearly well used, the brass handles show a good patina to the shape of his hands. On my other side, my great grandfather was a cabinet maker, I’ve also got his handsaw that’s seen just as much use, cast in steel in Sheffield during the big steel boom. For me, these objects are great examples of how well-made products can last a lifetime, and just like me, be cherished by younger generations to come.

Two of my separate great grandfather's tools, both nearly 100 years old, still in good shape.

But how do you design products to age gracefully? That comes down to understanding the right materials for the job. Generally, it means staying away from painted surfaces, unless you’re confident that when the paint eventually wears away it will still look good just like the Leica camera above. It’s also about knowing the type of life this product will be exposed to, will it be used every day? Can you maintain the product easily? Can parts be replaced if they break? All these questions should be answered to create products that can be used again and again and hopefully, be handed down to the next generations: still in good nick.

Principle 5: The construction is honest and transparent.

When you look at a product and can see clearly how it’s been constructed, for me it makes it look even better. When you try to hide how a thing has been made using covers and fascias, well for me that’s missing the point.

The engine on the left had been made using transparent construction techniques, whereas the BMW engine on the right has a plastic cover and “go faster holes” designed to make it look more ‘aggressive and manly’.

This sort of design appeals to a particular type of person, which I guess is like me, those that are fascinated with how things work. I don’t think this is a small group of people, why else would mechanical watches have clear backs?

Every rivet, dial and engraving have a purpose, which for me, makes this mesmerising.

“When you’re a carpenter making a beautiful chest of drawers, you’re not going to use a piece of plywood on the back, even though it faces the wall and nobody will ever see it. You’ll know it’s there, so you’re going to use a beautiful piece of wood on the back. For you to sleep well at night, the aesthetic, the quality, has to be carried all the way through.” — Steve Jobs

The other benefit from this approach is that the customer can understand the way that the product was made, and in doing so achieve a few things. Firstly you make it clear to them the amount of effort that was put into making the design as good as it can possibly be. The next is that by being transparent in how it’s been made, you can allow your customers to maintain, repair and replace any elements they want. This increases the longevity of the product itself, and in doing so improves the likelihood it will be used for years to come.

What are the important elements behind the designs you do or appreciate? As I learn more about the world of making physical products I’m sure this list will grow but for now these five act as a solid foundation for the things I want to create.

Alex is a product designer and entrepreneur. He is director of Parallel Products that makes well considered, personalised products.