The tricorder tools are finished well enough to test their function. The tools have been fitted to the relevant injection moulding machines and used for the first time to run off a set of trial parts; this step is called ‘first shots’.
As this project has moved through its development, our confidence that the tricorder really is moving out of fantasy and into reality has increased with each step. Even though each one of those steps have felt like major milestones, the practical leap to ‘first shots’ really is a genuine watershed. It is the first hard evidence that all the plans, the dreams, late nights, and hard work are actually coming together to create something solid, something real, something, dare I say it, good!
Nothing can quite describe the feeling you get the first time you get your hands on an almost-production-ready version of the product you have been developing for so long. For the tricorder project, it’s a moment we’ve been looking forward to since the very first kick-off meeting, way back when. Again, the integrity of the design is apparent. Personally, I’m struck by how much more compact it is than I thought it was going to be, even though I have already held the 3D model – I think that is something to do with the combination of the size plus the finished weight and solidity of it. To me anyway, that combination certainly feels about perfect. Although not a technical term, the word that springs to mind is ‘meaty’… and it is satisfyingly so. It’s compactly weighty, without being over heavy, in a way that says its volume will be filled with tech promise. It feels tight and balanced. On the whole, even though these are first shots, it’s neat and accurately finished in a way that shouts real-world production kit.
The disc ejection mechanism works as expected. Push any disc about a quarter of an inch (5 mm) inwards with the tip of your thumb until a satisfying click tells you that the disc is ready to be ejected; release the pressure and the disc slips out, protruding by the perfect amount to grip it between thumb and forefinger in a way that I know will be repeated, over and over by every owner just for the fun of it.
Changes can still be made at this stage, but they are typically (hopefully) limited to small adjustments: minor technical refinements to the fit and function of each part to improve how they work together. 3D printing can only take the design so far, as injection-moulded parts made in the correct materials behave differently – better, it is always hoped – obviously. With foresight, where possible, most of the parts have been designed so that where changes are required, the affected components only need to be made bigger in certain areas to refine the fit at critical points. When this is the case, the tool revisions are relatively simple, ‘metal-off’ changes, where only a small amount of machining is needed to make sure the moulded components fit together perfectly. For problems that go the other way, where the fit is too tight and less of a component is needed, then ‘metal-on’ changes are required. Metal-on changes are more difficult and time-consuming and, as the name implies, involve adding metal to the tool (by welding or fitting an insert into it) to enable further machining back to make the new revised cavity or core. As some degree of tooling modification is almost always required, this step is a planned-for stage of the project, typically referred to as ‘tool touch up’.
Main patterns and particular surface features that are part of the underlying design are included in the tooling, but at this stage the tool cavities haven’t been properly finished. They aren’t polished, plated or patterned with any fine surface textures, and won’t be until we are happy that the parts are just how we want them and performing exactly as they should.
The first shots are a big test of every part of the mechanical design and its translation to the production phase of the project. It’s also the injection moulding tooling’s first trial run which enables the moulding shop to see how the tool cavities perform and what minor adjustments of flow, cycle time and temperature profiles will need to be optimised in order to minimise any shrinkage and sink marks that will affect the mechanical performance and aesthetic appearance of the finished parts.
As the different areas of the development are running concurrently, this is the first time that all the mechanical parts have been assembled together with the functioning electronics inside it. Making the jump from the bench rig into the production unit, with the proposed production chipset, is a critical move and allows the internal sensors to be tested in situ. It enables the electronics team to check if there are any unexpected issues when all the internal (and external) sensors are working with each other in the same vicinity. Factors that are difficult to replicate or accurately predict on the bench, such as thermal effects and component cross-talk, can be observed directly.
To help the transition, a special development screen dynamically displays the status of the sensors on the LCD, and code has been written that allows the development software to be updated via the USB port, to avoid having to open the hood and dismantle the assembly to make software updates. The software is complex (for us, at least) and will require months of trials and study as it now moves towards the optimised production version.
After nearly three year’s work, as milestones go, ‘first shots’ is a biggie. Seeing the injection-moulded parts assembled together for the first time stirs some strong feelings in the hearts of engineers not normally known for getting emotional.
Coming next time
Edith Keeler – Developing content
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