Project Objective: Automate the gluing and pressing of frets into guitar necks for Paul Reed Smith (PRS) to reduce dependency on skilled labor and high turnover rates. The goal was to create a system where a skilled operator was no longer needed for this stage of the process.
Project Requirements:
Cost-effective compared to training and hiring new employees.
Maintain or improve current quality and speed of operation, with a focus on significantly increasing speed.
Minimize manual labor and allow for minimal human intervention.
Ensure frets are fitted flush to the fretboard with consistent glue application.
Mechanical and Sensing Sub-Systems
Detection & Gluing System:
A laser detection system identifies the location of every empty fret slot, ensuring precise alignment for glue and fret placement. This alignment process needs to be performed only once and can be applied to partially fretted boards.
Once the system detects open slots, the glue arm applies a precise amount of glue to 3-5 slots simultaneously in a square wave pattern. The number of slots chosen is based on the glue's drying time and the system's operating speed.
Fret Feed & Press:
Pneumatic Fret Feeder and Pressing Arm: This system component was designed to automate the process of pulling fret wire directly from the spool, cutting it to length, and pressing it into place. This innovation eliminates the manual step of pre-cutting frets to length. The feeder pulls the wire, straightens, and forms it through a series of bending steps to achieve the necessary bend radius. The wire is then fed forward, cut to a specified length by a pneumatically driven cutter, and the process is repeated for each fret.
Linear Carriage:
Custom Stepper Motor Driven Linear Stage with Fretboard Alignment Platform: This subsystem accurately drives the fretboard to ensure each operation occurs at the precise location. A high-precision linear encoder tracks the stage's position throughout the process, complemented by two limit switches at the beginning and end for automatic and precise homing and position control. Initially designed with a hold-down "finger," it can be upgraded to a vacuum hold-down for future revisions to enhance stability and performance.
Electronic Sub-Systems
Arduino Daughter Board
The system's core is an Arduino Mega with a custom daughter board that converts low voltage control signals to high voltage output drivers. Designed with several safety interlocks, the system ensures user protection and operates by pressing two buttons to initiate the control system. If any interlock is triggered, the system will not run. All code, written in C++ using custom and open-source libraries, was thoroughly documented. Detailed documentation on the code and electronics was provided to PRS, along with a comprehensive training walkthrough upon delivery.
Electronics Box
All the electronics were housed in a single enclosure, carefully wired and assessed by a certified electrician prior to delivery. To accommodate future servicing or upgrades, we used standard XLR and 1/4” audio connectors for wiring motors, sensors, and valves. This choice not only facilitated ease of maintenance but also resonated with the company's guitar manufacturing culture, adding a familiar and personal touch to the product.