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SpoolBuddy Assembly Guide

This guide walks you through assembling the SpoolBuddy from 3D-printed parts and electronics. Follow the steps in order — each section builds on the previous one.

SpoolBuddy assembly — front angle SpoolBuddy assembly — three-quarter view SpoolBuddy assembly — side profile

Assembly Video

Prefer to watch instead of read? The full assembly walkthrough is available on YouTube:

Watch on YouTube

Download Printed Parts

All parts are designed for SpoolBuddy and printed in PLA or PETG. Download the full project as a single .3mf file (recommended — all parts pre-arranged for slicing) or grab individual .stl files if you only need specific pieces. The editable .f3d Fusion 360 source is also available if you want to tweak the design.

SpoolBuddy.3mf — full project (all parts)

SpoolBuddy_V2.1.f3d — Fusion 360 source

Part File Description
Case — Part 1 (Electronics) case_part_1_electronics.stl Electronics base — holds scale module, display rail guides
Case — Part 2 (Scale) case_part_2_scale.stl Scale housing — load cell channel, joins to Part 1 via dovetails
Case Cover case_cover.stl Lid for the scale housing (Case Part 2)
Case Back Cover case_backcover.stl Back cover for the main enclosure
Display Holder display_holder.stl Back bracket for the display, screws to case
Display Cover display_cover.stl Front bezel frame, clips over the display
NFC Reader Cover nfc_reader_cover.stl Cover for the PN5180 module on the spool plate underside
Spool Holder - 10mm Version spool_holder.stl Spool plate — mounts on load cell (10mm), holds filament spool
Spool Holder - 15mm Version spool_holder_-_15mm.stl Spool plate — mounts on load cell (15mm), holds filament spool
Spool Stopper spool_stopper.stl Curved arc, clips into spool plate rim

Parts Inventory

Before starting, confirm you have all printed parts:

Part Qty Notes
Case Part 1 — Electronics 1 Holds scale module, has display rail guides
Case Part 2 — Scale 1 Load cell channel, dovetail joins to Part 1
Case Cover 1 Snaps onto Case Part 2 (scale housing)
Case Back Cover 1 Closes the back of the case, shared screws with display holder
Display Holder 1 Bracket screwed into display standoffs, slides into case rails
Display Front Cover Frame 1 Beveled bezel frame, clips over the front of the display
Spool Plate 1 Multiple hole positions for adjusting distance from display
Spool Stopper 1 Curved arc, clips into spool plate cutout
NFC Module Cover 1 Clips onto spool plate underside

Hardware Required

Screw Qty Used for
M4 × 25 mm hex socket 4 Load cell → Case Part 2 (2), Spool plate → load cell (2)
M3 × 5 mm self-tapping 2 Display assembly → case rail lock

Before You Print — NFC Module Cover

Do this before printing the NFC Module Cover

The NFC Module Cover has a circular wire exit hole on the right side. If your NFC wiring requires a larger or differently shaped cutout, use a negative body/part in your slicer to enlarge it before printing. It is much easier to do this now than to modify a finished print.

Step 1 — Join Case Part 1 and Case Part 2

  1. Align the two dovetail joints on Case Part 1 (Electronics Base) and Case Part 2 (Scale Housing)
  2. Slide the two parts together until they are fully seated
  3. No screws are required — the dovetails hold the parts together firmly
  4. If you want extra rigidity, a small amount of superglue can be applied to the joint, but this is usually not necessary

Step 2 — Install the Scale Module (NAU7802)

  1. Place the NAU7802 PCB onto the 4 standoffs inside Case Part 1
  2. Press down until the board seats on all four standoffs
  3. Route the NAU7802 cables through the oval cable routing hole in the case wall

Step 3 — Mount the Load Cell

  1. Lower the load cell beam into the channel in Case Part 2 from above
  2. Secure it with 2x M4 × 25 mm hex socket screws through the top holes
  3. Route the load cell wires through the oval cutout on the side wall of Case Part 2

Step 4 — Fit the Case Cover

  1. Align the Case Cover over Case Part 2 with the open gap facing the front (towards the load cell beam)
  2. Press down until the two rear clips snap in and hold the lid in place
  3. The front gap is intentional — it allows the load cell beam to pass through freely

Step 5 — Display Sub-Assembly

LAFVIN display standoffs

The LAFVIN 7" HDMI Touch display comes with standoffs in the box. Use these to mount the Raspberry Pi — no separate standoffs are needed.

  1. Mount the Raspberry Pi onto the back of the display using the included standoffs
  2. Connect the HDMI and USB cables between the Pi and the display
  3. Attach the Display Holder to the back of the display — press it onto the display standoffs
  4. Press the Display Front Cover Frame onto the front of the display until the retention clip engages

Step 6 — Install Display Assembly into Case

  1. Tilt the display assembly at an angle and align it with the two sliding rail guides on Case Part 1
  2. Slide the assembly along the rails until it is fully seated

Step 7 — Install Case Back Cover

  1. Place the Case Back Cover against the back of the case, aligning it over the display holder
  2. Fasten the 2x M3 × 5 mm self-tapping screws into the Case Part 1 holes to lock the display assembly in place

Step 8 — Spool Plate Sub-Assembly

  1. Mount the PN5180 NFC module into the bracket on the underside of the spool plate
  2. Route the NFC cables through the wire cutout in the NFC Module Cover
  3. Clip the NFC Module Cover onto the underside bracket — it secures with side clips, no screws needed

Step 9 — Mount the Spool Plate

  1. Choose a screw hole position on the spool plate based on how far you want it from the display
  2. Lower the spool plate onto the load cell, aligning the chosen hole with the load cell mounting point
  3. Secure with 2x M4 × 25 mm hex socket screws from the top

Step 10 — Attach the Spool Stopper

  1. Align the curved spool stopper arc with the cutout on the spool plate rim
  2. Press/clip it into place — no screws needed

Assembly Complete

Your SpoolBuddy is now fully assembled. Before powering on:

  • Check all screw connections are snug
  • Confirm the load cell beam moves freely through the case lid gap
  • Verify NFC module cables are routed and not pinched
  • Plug in the angled USB-C connector to the Pi's USB-C port — the cable exits through the cutout on the back of the case

Proceed to the Installation guide to set up the software.