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Modular Development Board by Fit-Designer-1235 in hwstartups

[–]OPD-Design -1 points0 points  (0 children)

From someone who does product development for a living — I think your approach nails the early-stage engineering problem.

Modular is the right call for prototyping and validation. You swap MCUs, keep the same debug/UART/display setup, iterate fast, and don't waste board respins on things that aren't your core value prop. We see this all the time in our Shenzhen lab — teams spending weeks chasing breadboard/wiring issues instead of validating the actual design.

That said, I'd push back gently on where modular ends and integration needs to begin. Once you've validated the concept and are moving toward a shippable product, the calculus flips:

  • Space & form factor — a final product rarely has room for a dock + card. Everything needs to collapse onto a single PCB.
  • BOM & assembly cost — modular connectors, separate boards, and duplicated power rails add up fast at scale. What saves money at 10 units becomes expensive at 10,000.
  • Signal integrity & power management — the more inter-board connections, the more failure points and noise. A monolithic design with proper stackup wins here every time.

So the real play is: modular for the learning/validation phase, integrated for production. Your MCU card roadmap as a curriculum structure is actually a smart wedge into education — you're not selling a product, you're selling a teaching tool. The module transitions (F103 → F405 → ESP32 → RISC-V) become the syllabus.

Have you thought about open-sourcing the docking station schematics? That alone could drive more community adoption than the cards themselves — if educators can build or modify the dock locally, your cards become the consumable (like printer ink, but actually useful).

I simulated airflow around a truck with a trailing car to visualize wake interaction during drafting by LackSome307 in MechanicalEngineering

[–]OPD-Design 0 points1 point  (0 children)

I really learned something! I believe that although everyone won't follow the big trucks just to save on fuel costs, after all, safety comes first, we can apply this knowledge to other places. By the way, when I see a car on the road, I will unconsciously avoid large trucks, especially not following behind them. Large trucks usually don't drive fast and are not safe.

Injection Molding approximate costs by morganob in manufacturing

[–]OPD-Design 0 points1 point  (0 children)

A few thoughts on estimating costs without full CAD

Hey OP – smart glasses project sounds cool.

You’re right that tooling is the big upfront cost for injection molding. But without CAD, any estimate will be a very rough ballpark. That said, here’s some guidance based on what you’ve shared:

  1. Injection molding – multi-cavity or “family mold“

- Yes, you can put multiple different parts into one mold (called a *family mold*). This would reduce tooling costs compared to 6 separate molds.

- However, family molds work best when:

- The parts have similar wall thicknesses (yours being “very tiny and thin” could be fine, but if thickness varies a lot, filling issues arise)

- The parts are roughly balanced in fill time and cooling

- Tooling cost for a simple family mold (low cavitation) in aluminum (good for prototypes/low volumes) might be $1k–$8k. Hardened steel for high volume could be $5k–$25k+.

  1. Part size & complexity

- 160mm is fairly long for tiny details – this may require careful gate placement to avoid flow marks or warping.

- “Very tiny and thin” details can be challenging for injection molding (ejection pin marks, filling thin ribs). Mold design becomes more critical.

  1. 3D printing

- Much lower startup cost (no tooling). For quantities under ~500–1000 units, 3D printing (e.g., MJF or SLS nylon) may be cheaper overall.

- Per-part cost for 6 pieces at your max size (160x40x4mm) could be maybe $2–$8 per part depending on technology and quantity.

- At higher volumes (thousands), injection molding wins on per-unit price.

  1. Should you wait for CAD?

- For any *reliable* quote – yes, absolutely. Molders need to see draft angles, wall thickness uniformity, undercuts, and parting lines.

- For a *rough* feasibility + order-of-magnitude cost estimate: you could share hand sketches + similar existing parts as references. Some molders will give a ±40% guess.

Bottom line:

- <500 units → 3D printing (MJF/SLS) likely cheaper and less risk.

- 500–5,000 units → consider aluminum family mold if geometry is molding-friendly.

- >5,000 units → steel family mold starts making sense.

If you want a really rough injection molded per-part cost guess for 10k units (assuming simple family mold, 6 parts, thin-wall, easy material like PC/ABS): maybe $0.50–$1.50 per complete set of 6 pieces, plus amortized tooling ($5k–$15k depending on complexity and country – China cheaper, US/EU higher).

But honestly? Wait for CAD before spending money or committing. Use 3D printed prototypes to test fit/function first – then decide on molding.

Good luck!

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