Precision Machine Design and Instrumentation- Fall 2019 course project
Goal: Design a machine that automates the entire process of fretting guitar necks. This includes the entire process from cutting the slots for the fret wire to precisely grinding down the sides of the guitar neck. The machine had to accommodate many different sized guitar necks and shapes.
My contributions included:
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Design the fret wire feeding and cutting module
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Calculate the proper sizing for the motor, pneumatic air snipper, weight sensor, and linear drive
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Design a custom fixture that can:
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Accommodate any size guitar neck
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Lock onto to the linear drive and easily slide on and off the conveyor belt
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Mock up a user interface for the machine operator
Automated Guitar Fretting Machine
by Caroline Carbo, Kara Krone, Shai Almagor, and Alice Wei
Fret wire feeding and cutting module
A weight sensor underneath the spool feeds back to the software to let the operator know when it is time to change out the spool.
Most of the components in this module were sourced from manufacturers and sized appropriately to the size of fret wire.
The springs give the friction force for the drive and allow for the adjustment in size depending on the size of the fret wire.
The fret wire is fed from a spool through a friction drive feeder and cut by pneumatic air snippers.
The entire module is mounted on a linear belt drive that can move the system toward and away from the guitar neck.
The custom fixture had to adjust to hold guitar necks that had a radius at the top of 10"-16", variable widths along the length of the neck of 1.69"-2.25", scale sizes of 24-25.5, and any standard shape. We decided to zero the z-axis of each neck at the top of the fixture. This was accomplished using telescoping tubes that lock into place. The rounded part of the neck is fixtured with a V-shaped jaw.
The fixture slid into a rail system on the linear drive and was locked into place using two pneumatic stopping pistons. Even though the fixture can adjust in length, the length of the rail is always the same so the lock is a tight fit. The front portion of the fixture extends past the linear drive to aid in the transition off of the drive onto the conveyor belt.
Other things to note about the fixture:
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It is capable of accommodating any head shape, including extreme downward bending, like in the model.
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The nut is considered the zero on the musical scale and fret placement is measured from the nut.
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The front of the fixture slides right up against the nut so that the position sensor in the machine can find the zero point from which to measure each slot to cut.
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The fixture takes up much less space than would be needed for even the shortest distance to the first fret.
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The extended portion at the front of the fixture will not bump the pneumatic stopping piston. There is a gap so that the piston can be in the stopping position while the fixture is slid onto the linear drive.
Custom Fixture
User Interface
There is only one operator who sets up the machine before each use. This is a mock up of the machine's software. There are weight sensors under each rack and the spool of fret wire which are indicated by the green bars.
Here is the link (it will open in a new window):
https://docs.google.com/presentation/d/1ws_gRzKiV0ce7k6kpvw8nioSuJkJI9jTeX_PBhnBarw/edit?usp=sharing