Dev Update #2: Parametric CAD, and support for SG90

[jamro]

The first version of Tiny Software Engineer was built around one servo. That worked, but it also locked the 3D parts to that one body size. If you bought something slightly different, pockets didn’t fit, and there was no clean way to resize the robot without redesigning it by hand.

That’s the opposite of “easier to build.”

So the CAD is now parametric.

The Fusion model (TinyEngineer.f3d) drives printed pockets, mounting tabs, shaft clearance — and the size of the whole robot — from servo dimensions. Change those parameters, and desk, chair, body, and mounts rebuild around the servo you actually have.

📐 What that means in practice

You pick the servo first. Then you print the matching parts.

There are presets for:

• Tower Pro SG90: easiest to buy, larger desk, electronics easier to fit and assemble
• Feetech FS0307: more compact
• PowerHD HD-1370A: still there for the original V1 build

I tested the SG90 path with a Tower Pro SG90. That’s the unit the preset is based on.

If you use a different servo (including another "SG90" from a different seller) dimensions can differ. Clones are not identical. Don’t assume the ready-to-print files will fit.

In that case, open the Fusion parametric model, measure your servo, adjust the user parameters (or add a preset), and export parts that match your hardware. There’s a ServoSizingTester part for checking pocket fit before you print the whole robot.

Docs: Parametric design

🎯 Why this matters

The goal from Dev Update #1 is still the same: make the robot reproducible for software engineers who haven’t built hardware before.

Standardizing on one easy-to-find servo helps. Making the CAD parametric helps even when the servo isn’t an exact match.

You shouldn’t have to reverse-engineer the enclosure because your micro servo is 0.5 mm thicker than the one I used.

What’s still in progress

This is CAD and documentation work toward a more reproducible build. I’m not calling it a new product drop.

Still on the list from last time: print-service-friendly models, simpler electronics, and less wiring.

If you’re thinking about building one: would you rather buy the widely available SG90 and live with a slightly bigger robot, or hunt for a smaller servo and print a more compact set of parts?

[jtruland]

I've started printing the non-parametric design and sourced the HD-1370A, but I haven't been able to source the original OLED. What, if anything, do I need to re-print as 1370 to be able to use the Waveshare OLED?

[jamro]

In this case, you don’t need to reprint all the parts. You can use the Head + Hat + Neck from the new parametric model (HD-1370A version) and keep the rest of the robot from V1.

Since the neck mounts directly onto the servo shaft, it should be compatible. The overall head dimensions will be slightly different, but that shouldn’t matter.

[jtruland]

Thanks! I was hoping that was the answer.

…

On Fri, Sep 11, 2026 at 12:12 AM Krzysztof Jamroz ***@***.***> wrote: In this case, you don’t need to reprint all the parts. You can use the Head + Hat + Neck from the new parametric model (HD-1370A version <https://github.com/jamro/tiny-engineer/tree/main/3d_models/parts/hd1370a>) and keep the rest of the robot from V1. Since the neck mounts directly onto the servo shaft, it should be compatible. The overall head dimensions will be slightly different, but that shouldn’t matter. — Reply to this email directly, view it on GitHub <#28?email_source=notifications&email_token=AJAX6KGQW5QPGP6TXJQLZTL5ON3T5A5CNFSNUABIM5UWIORPF5TWS5BNNB2WEL2ENFZWG5LTONUW63SDN5WW2ZLOOQXTCOBTHE2TAMBYUZZGKYLTN5XKOY3PNVWWK3TUUVSXMZLOOSWGM33PORSXEX3DNRUWG2Y#discussioncomment-18395008>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AJAX6KE24SQE2F4GTC2E2DT5ON3T5AVCNFSNUABJKJSXA33TNF2G64TZHMYTGNBRHE4DMNJQGQ5UI2LTMN2XG43JN5XDWMJQG44TAOBTG2QXMAQ> . Triage notifications, keep track of coding agent tasks and review pull requests on the go with GitHub Mobile for iOS <https://github.com/notifications/mobile/ios/AJAX6KEHY4A4HSY6AFRLG3T5ON3T5A5CNFSNUABIM5UWIORPF5TWS5BNNB2WEL2ENFZWG5LTONUW63SDN5WW2ZLOOQXTCOBTHE2TAMBYUZZGKYLTN5XKOY3PNVWWK3TUUVSXMZLOOSVGM33PORSXEX3JN5ZQ> and Android <https://github.com/notifications/mobile/android/AJAX6KGWVN4DRTSOQHXZWZ35ON3T5A5CNFSNUABIM5UWIORPF5TWS5BNNB2WEL2ENFZWG5LTONUW63SDN5WW2ZLOOQXTCOBTHE2TAMBYUZZGKYLTN5XKOY3PNVWWK3TUUVSXMZLOOSXGM33PORSXEX3BNZSHE33JMQ>. Download it today! You are receiving this because you commented.Message ID: ***@***.***>