NBN Sorter - Automated Bolt, Nut & Washer Sorting Machine

A mechatronics project by students of **Kasetsart University Sriracha Campus**
Industrial Engineering Program

Project Overview

NBN Sorter is an automated mechanical sorting machine designed to separate mixed hardware fasteners — bolts, nuts, and washers — by type and size (M3, M4, M5) without human intervention.

The system uses a combination of gravity-based rail sorting, magnetic conveyance, rotating disk mechanisms, and a real-time TFT dashboard to classify and count each fastener type.

Input: Mixed bolts (M3/M4/M5), nuts, and washers poured into the input hopper
Output: Sorted fasteners separated into individual collection bins by size and type

System Architecture

The machine consists of 4 stations connected in sequence, plus a display/wiring unit:

Station Details

Station 1 - Rail Sorter

• Mixed fasteners are poured at the top-right input hopper

• Gravity guides bolts along one path to Station 2

• Nuts and washers slide down to separate sorter rails

• An adjustable gap mechanism separates by thickness:

  • 1.2 mm gap → washers pass through
  • 3.8–4.1 mm gap → nuts pass through

• An acrylic cover guide prevents parts from bouncing off due to motor vibration

• Spring-loaded coupling increases incline force to prevent jamming

Accuracy: 85% (255/300 over 10 test runs)

Station 2 - Pink Box (Bolt Feeder)

• Receives bolts from Station 1
• Internal rotating disk with hidden magnetic buttons picks up bolts individually
• Bolts are lifted and guided along a rail to Station 4
• Magnetic hole offset: 2.0 mm (optimal for single-bolt pick-up)
• Guide rail incline was increased to reduce friction-related jamming

Accuracy: 39% (39/100 over 10 test runs) — lowest performing station; main bottleneck

Station 3 - Rotating Plate (Nut Sorter)

• Receives nuts from Station 1

• A rotating disk with a fixed semi-circle plate directs nuts into size-based curve paths

• Sorting gap parameters (distance between rotating plate and fixed semi-circle):

  • M3 section: 4.4 mm
  • M4 section: 3.5 mm
  • M5 section: 2.8 mm

• Drive system: bevel gear reduction at 1:4.5 ratio (replaced original belt-pulley drive)

• Front support added to the semi-circle plate for perpendicular stability

Accuracy: 97.6% (117/120 over 10 test runs) — best performing station

Station 4 - Magnetic Conveyor (Bolt Sorter)

• Receives bolts from Station 2
• Bolts attach to magnets embedded in the conveyor rail surface
• As the belt moves, bolts drop into M3/M4/M5 collection boxes below
• Wall thickness between bolt and magnet: 1.5 mm offset (optimal release force)
• Gear ratio: 1:3
• Conveyor belt uses custom-designed PLA linkage (replaced thin metal wire)
• Rail designed from scratch in SolidWorks with embedded magnet holes

Accuracy: 64% (64/100 over 10 test runs)

Display & Wiring — NBN Dashboard

• Built on ESP32 with TFT eSPI display
• GUI rendered using LVGL library
• Displays real-time count of sorted bolts (M3/M4/M5) and nuts/washers
• Serial communication with sensors via circular buffer
• Dynamic label updates via updateUI() function based on sensorOut\[] array

Overall Results

Station	Component	Accuracy
Station 1	Rail Sorter	85%
Station 2	Pink Box	39%
Station 3	Rotating Plate	97.6%
Station 4	Magnetic Conveyor	64%
Overall System	End-to-end (3 runs)	40.95%

End-to-End Test Summary (3 runs)

Size	Bolt	Nut	Washer
M3	26.6%	40%	—
M4	3.3%	40%	—
M5	10%	80%	—
OTHER	—	—	90%
Category Total	35.71%	30%	57.14%

Overall system accuracy: **40.95%**

Known Issues

• Station 2 (Pink Box) is the primary bottleneck — magnetic clumping causes multiple bolts to jam together
• Washer sensor reads 0% — washers could not be detected reliably in the dashboard
• Bolt detection in the dashboard is slow and error-prone
• PLA deformation requires manual filing with vernier caliper to maintain tolerances
• End-to-end accuracy is limited by inter-station transfer reliability

Design Iterations

The machine went through 6 design versions before reaching the final build, iterating on:

• Structural layout and station arrangement
• Drive systems (belt-pulley → bevel gear reduction)
• Conveyor belt material (metal wire → PLA linkage)
• Sorting gap dimensions (empirically tested)

Team Member

• Chanaprachpakorn Ngernmo
• Theerapol Guanmuangtai
• Thanakrit Wongkha
• Warut Tongrung
• Norawich Lorttrakanont
• Kunasin Laysak
• Danuphat Parnpradit
• Thanakon Chaichana
• Jerich Brylle Sison
• Sajakorn Chutikarnmongkol

Institution

Kasetsart University Sriracha Campus
Industrial Engineering Program

This project was developed as part of an academic engineering design course. Full Demonstration Video: 🔗 Watch on YouTube