Spool Inspector
Place a spool on the scale. The Inspector scans the QR code or reads its RFID tag, weighs the spool, and syncs everything to your account in seconds. Remaining filament, project costs, even storage location — all without touching your phone.
Owning one unlocks Pro features, free. Build it or buy it — your first weigh unlocks full Reports & 20 AI scans/month, free for as long as you have a device. Buy an assembled unit and the code in the box adds 3 months of Pro (a full year with an Inspector RF).
RF units are in stock now. Already own an Inspector? A $10 upgrade board retrofits it if you're comfortable soldering — see the retrofit guide. A fitting service is coming later this year.
Adding a second scale? Each additional RF unit is $35 off — one at the printer, one at the filament shelf. Already own an Inspector, or already on Pro? You’re eligible for the same $35 off, since the free Pro year in the box would be doubling up on what you have — your code is in Settings → Plan.
Hardware
How it works
Place spool on the scale
The scale detects weight over 50g and begins stabilizing.
It identifies the spool
The autofocus camera locks onto your QR label and reads the spool ID — or, on an RF unit, the reader picks up the spool's RFID tag.
Data syncs instantly
Weight, remaining filament, and project costs update in your account automatically.
Set location (optional)
A prompt asks if you want to update the spool's storage location. Pick from your list or skip.
Remove spool
Take the spool off. The station resets and is ready for the next one.
Features
Automatic QR Scanning
Place a spool on the scale and the autofocus camera reads its QR code automatically — no manual entry needed.
RFID Tag Reading
An added NFC reader recognises a spool from its RFID tag as it lands on the platform, and writes blank tags so generic and refill spools identify themselves too. It works alongside the camera rather than replacing it — the camera still reads QR labels and anything without an RFID tag.
Precision Weighing
A load cell weighs down to the gram. The system subtracts the empty spool weight to calculate remaining filament.
Instant Sync
Weight readings sync to your account in real time. Remaining filament, project usage, and material costs all update automatically.
Set Spool Location
Update a spool's storage location right from the device. Moving a spool to the printer? Scan it and set the location — no need to open the app.
Near-Empty Detection
When a spool has less than 10g remaining, the device prompts you to mark it as empty. Never start a print with an empty spool again.
Scale Mode
Turn the Inspector into a plain digital scale — weigh anything, not just spools. No camera, scan, or syncing; just a live, stable readout. Auto-returns to Weigh mode after a few minutes idle.
Drying Mode
Scan a spool before your dryer cycle to record its start weight, then scan again after to capture how much moisture came out — drying history tracked automatically.
Five Modes
Cycle with a single button press: Weigh (update inventory), New Spool (calibrate empty spool weight), Set Location (move spools), Dry (log drying sessions), and Scale (weigh anything).
Offline Queue
No WiFi? No problem. Weighings are saved to flash memory and sync automatically when connectivity returns. No data is ever lost.
OLED Display
A built-in display shows weight, current mode, scan progress, WiFi status, and prompts — no phone or computer needed to operate.
Easy WiFi Setup
Long press a button to start the captive portal and enter WiFi credentials. From then on you can paste an API key straight into the device's own page on your network, scan a QR from Settings, or re-run the portal — your call.
Button reference
OLED indicators
Specifications
Bill of materials
Estimated total parts cost: ~$60 (excluding tools and 3D printing filament). Or get a complete kit from 3dcreator.shop. Building the RF version? Add the PN532 RFID board ($10), or start from the RF DIY kit.
Some links below are affiliate links. We may earn a small commission at no extra cost to you.
Headers, fasteners, and wire typically sold in bulk packs. This crimper kit (paid link) includes the crimper, housings, and pins. Or skip the crimping and grab a pre-made cable set from 3dcreator.shop.
Important: Direct-wire the load cell
Do not use Dupont connectors on the load cell wires. Solder them directly to the PCB pads. Dupont connectors cause intermittent contact issues that lead to weight drift and unstable readings. The OLED and button connectors are fine — this only applies to the load cell.
STL files provided. ~450g of filament total. Don't have a 3D printer? Get the pre-printed parts from 3dcreator.shop.
Most 3D printing hobbyists already have these tools
Thermal label printer for printing QR code spool labels. Works with our label export feature.
Get one
Every part you need to build a Spool Inspector — source nothing yourself. Already have some parts? Exclude them at checkout and pay less.
- ✓All electronics, hardware, and connectors
- ✓Base PCB set included
- ✓Optional add-ons: pre-crimped cables, USB, scale
- ✓Customize — exclude items you already have
- ✓You 3D print the enclosure (STLs provided)
Just the main + button boards. Source the rest yourself using the BOM below.
- ✓Main board + button board
- ✓Pre-compiled firmware via web flasher
- ✓BOM, STL files, and assembly guide
- ✓Source parts yourself (~$50 more)
- ✓Same features as pre-built
Fully assembled, tested, and ready to go — just plug in and connect. Two versions: camera-only at $99, or the RF at $125, which adds the RFID tag reader.
- ✓Fully assembled and tested
- ✓3D printed enclosure included
- ✓Firmware pre-loaded
- ✓OTA firmware updates
- ✓RF reads spool RFID tags as well as QR labels
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