USB Powered Servo Driven Agitator Table for PCB Etching

When making hobby Printed Circuit Boards (PCB), one method requires an acid bath (most often ferric chloride) to dissolve (etch) away the copper that's not needed in the "traces" for the circuit. This project describes how to use a servo motor to make an agitator table (more like a gently wave machine) for etching PCBs and uses a Parallax Continuous rotation servo, with a standard "horn", and a Servo "Tester" to drive the motor. If you have the parts, you can be up and running with this project in about an hour. Instead of the Servo tester, you could use an Arduino Nano to control the servo.

The design is laser cut and can use 3D printed legs, or the arched supports that are in the laser cut design. You can also cut this out by hand using project board and a hot glue gun.

The servo is connected to the sliding table that support the "bath", with a wire, which provides a way to de-link the bath if needed. Varying the distance from the attachment point of the wire, on the servo horn (higher torque center of the horn), to the ends of the horn or changing the Test mode between slow, fast and sweep, can produce different wave patterns. A small container holds the PCB that you want to etch (usually face down).

The project costs under 30$, and you can probably get that down under 20$

- Servo tester (about 6 dollars) or less from Geek, has multiple modes.

- Parallax continuous rotation servo motor (under 15$)

- USB inline switch, just for convenience (under 2$)

- 1/8 (~3mm) inch board about 2' square "Hardboard" or project board and a hot glue gun

There isn't much to this project.

If using a laser cutter, download the SVG file for the cut (for a 40W CO2 Laser I used speed 130, power at Full), for engraving the wave design (clipart from internet) I used speed 400 and power at 20), your settings may vary.

If cutting this out by hand, from project board, or even foam board, use the pdf file to print out the pattern and cut out the shapes by hand with an Exacto knife.

Glue the parts together (do not glue the sliding table to the support structure, or it can't slide).

The tabs are to keep the bath from wnadering off the sliding table.

You can 3D print legs instead of the arched wood supports ("Shaker Leg.stl"), or assemble the supports that were cut from the pattern. Then glue the assembled support frame to the top section.

You can also use other, smaller servo motors. Surprisingly these work very well.

One image above shows the cut out support structure and another shows the 3D printed legs.

https://youtu.be/63jRVdmIvnE

This is how the parts look after assembly.

Bend a small piece of fairly ridged wire to connect the sliding table to the Servo horn.

Choose the speed on the controller/test unit.

Vary the speed with the tester or by moving the wire out to the end of the servo horn.

I guess you could also make a custom horn (if needed).

The project runs off of USB and it ran it for 2 hours with no problem.

I've used this now for several PCB projects and it works great.