What determines the exact size/tolerances of a product?

Non-Industrial Designer here, might be a dumb question.
Who determines the exact dimensions of a product? Using a phone as an example, do the designers give requirements to engineers who might have some wiggle room as to how everything comes together, or is it the other way around? I know it probably depends on the product and how much testing/iterations are involved.

Who decides where to make trades like only having this exact space to put a battery or deciding the phone must be 3mm taller? I guess I’m looking at it as a huge organizational undertaking as much as engineering and design.

If we are talking about complex product configurations and supply chain networks, it is mostly a team effort with several designers and engineers closely collaborating after the initial concept phase.
Based on engineering (and all other) requirements the industrial designer typically determines final component arrangement, while design engineering typically takes the design freeze toward production level. Tolerancing for complex assemblies typically takes expertise in optimization of so many parameters that you need an engineering team. But a lot of industrial designers can do the hardware engineering as well for simpler products up to, say toasters.

There are a ton of factors. with something like a phone, there are industry standards on screen sizes usually driven by the LCD fab sizes and how to cost effectively split them up. Deviation is possible but costly. Then there are a bunch of other factors like module stack up (chips and board, and usually sensors) necessary antenna placements and clearances (usually there are 4-6 different kinds of antennas, some duplicates, and they usually can’t be near each other), battery size, I/O port size… yada yada yada. A lot of these things are defined by the product manager’s specs and the engineering constraints. When I’ve worked on smartphones a lot of what I’m doing is negotiating placement of these things. For example I worked on a phone about 10 years back that had a particular cross section to the back which was a direct response from the product brief, so there was a lot of working with the engineers to push and pull internal components to make that work.

The best analogy I can make to this is that it is like dancing with another person. You have to pay attention to what the other person is doing and create some kind of back and forth. When design is doing its job we are understanding all of the parameters and influencing the others in the dance (engineering and product management) to follow along, and we are doing that for a specific resin that will benefit the end user.

As others conveyed, a collaboration of what to do (designer) and how to do it (engineer).

And as a rule of thumb, the better the collaboration, the better the outcome.

definitely… and an open minded engineer is worth his or her weight in gold! I’ve worked with a few engineers in my career that I just loved. You tend to get in a groove together and I would show them a concept sketch before I would even show another designer.

Excellent, thanks for the replies. So I guess that’s not how they do things at Kramerica. :smiley:

Every piece of a stack has some constraints. For example, battery cells actually can grow slightly during use. In the old days the engineers would say “I need 2mm around the battery” and people would agree. As every 10th of a MM became more important you wound up getting to modern packaging constraints like stacking chips on top of each other, wild antenna configurations, and in the case of the infamous Galaxy Note explosions, a case that was actually too small to properly grow and caused explosions.

Most of these are based on the material property, the tolerance that the vendors can achieve with each part, etc. Adding all those tolerances up is considered the tolerance stack and you need to make sure that the design can accommodate the movement and shifting of parts.

Actually, the customer determines the dimensions.

Speaking of the customer deciding, many companies view the retailer as their customer, and many retailers have size constraints. I’ve worked on a few products that landed in Home Depot, The Apple Store, and Target. There were times where we had to redesign the packaging to meet their shelf requirements (luckily the product accommodated that…). If you are developing something that is made from sheet goods (like flat pack furniture for example) nesting and cut efficiency is going to impact dimensions as well… in the end, there are tons of factors depending on the industry.

This is truly a chicken and an egg question.

It is definitely a team afford between engineering and industrial design teams, I have lots of experience in designing consumer appliances, first step is to have very loose dimensional constrains determined by industrial designers in mind, that’s what engineers and technical team would use as a guideline to proof that technically the geometry can work, or not… and what must change in order for it to work.
Once a proof of concept and a working model are finalized, it’s time to make it pretty.
At this stage technical KPIs, aesthetics, ergonomics, packaging requirements, shipping constrains (how many boxes will fit into a shipping container) and more are all working as a team to come up with an amazing product.

Customers deciding – is a terrible idea! Customers often have literally fantasy desires which geometrically and functionally aren’t possible… at least not on this planet LOL


They decide with their money.

Lest you forget, small phones were all the rage just a few years ago.