Can you build another?
A working prototype doesn’t always mean you’re ready to build more.
The situation
A founder came to us with a haptic system that translated audio into physical vibration. The product used floor mounted platforms that a person could place their feet on, connected to a separate controller containing the electronics, audio processing, and firmware.
The product already worked. There were functional systems in use, along with mechanical designs, electronics, firmware, BOMs, and other engineering assets. The founder wanted to build more of them.
The ask was essentially: help us reproduce what we already have.
The plan
We brought together mechanical, electrical, firmware, and manufacturing resources and started with the existing product.
The idea was to use the working systems and available documentation as the reference, close any remaining engineering gaps, source the parts, and move into a small build.
On the mechanical side, there were already assembly sequences, enclosure designs, finishes, BOMs, and packaging concepts. There was also existing electronics and firmware. We had enough to begin working toward additional units rather than starting product development from scratch.
As the engineers got into the hardware, though, some of what looked complete from the outside became less clear.
Where uncertainty remained
One example was the audio system. The product produced the intended experience, but there wasn't a complete engineering specification describing exactly how the audio pipeline was supposed to behave. The team still had to understand signal paths, filters, wiring, power, grounding, and how the controller interacted with the haptic platforms.
The reference hardware wasn't always consistent either. Different team members had access to different versions of the product, and some units were incomplete or behaved differently from others.
That created questions we needed to work through before another team could reproduce the product. If one unit was wired differently from another, which one represented the intended design? If a component had been changed during debugging, was that now part of the product? If something worked in the prototype, could we source and assemble it the same way across the next batch?
We were trying to understand exactly what needed to remain true for the next one to work the same way.
What needed to be proven first
Before building more units, the team needed to turn those unknowns into defined engineering decisions.
We refined parts of the mechanical design, simplified wiring, developed a custom interface PCBA, updated firmware, worked through audio and grounding issues, sourced components, and began defining how the finished systems should be assembled and tested.
Each step gave us more confidence that the product could be reproduced by a team that hadn't built the original prototypes.
The work eventually moved into an 11 set build. At that point, we were assembling and testing multiple systems rather than relying on one working reference unit.
The original goal hadn't changed. The founder still wanted more of the product he already had. The work in between was figuring out what had to be captured, clarified, or changed before that could happen reliably.
The pattern
The first few units of a hardware product are often built by the same people who designed them. Those people know which board revision to use, why a component changed, how something should be wired, and what to try when the system doesn't behave correctly.
Not all of that knowledge necessarily makes it into the CAD, schematics, BOM, firmware documentation, or assembly instructions.
That can be fine while the original team is still building every unit. It becomes more important when somebody else needs to build the next 10, 50, or 100.
A working prototype shows that the product works as intended. Reproducing it with another team starts to show whether the product has been defined well enough to built repeatedly, with the same quality.
If you're in a similar spot
If you already have working hardware and you're preparing to build more of it, imagine handing everything you have today to a new engineering and manufacturing team.
Could they build another unit that works the same way without the original team explaining the decisions behind it?
If not, there may still be some development work between having a working prototype and having something you can reproduce.