Saturday, January 25, 2014

New agitator design.

This is my old agitator.  When I first started etching my own PCBs, I cobbled this thing together in about an hour.  While it got the job done, it was ugly, bulky, required a dedicated micro controller, and did not accommodate different sized containers.  I thought it was time for an upgrade...

I drew this thing up last summer.  The idea here was to mechanize the oscillation, to cut out the need for a micro controller and servo.  Also, I wanted to design the frame to be adjustable, to accommodate different container shapes and sizes.  This design would also allow anyone to build one for themselves without having to own the exact same glass container I use.

The brackets for the frame, and several other key components, can be 3D printed.  I'll be publishing the designs on thingiverse in the near future.

The most complex part of the design in the oscillator.  This will convert the radial motion from a 12v DC gear motor, to an up and down sine wave oscillation. 

I designed the 3d-printed bearing block to hold one 608 bearing, and two 8mm linear bearings (the former can be salvaged from old roller skates, both can be ordered from most 3d printer part suppliers.)

The "lever" for the oscillator can be made from a small chunk of aluminum.  I cut a bit off a scrap from an old project.

One hold should be drilled in the face of the aluminum block to accomodate the diameter of the motor shaft you're using.  Mine was about 5mm.  Another hole will be threaded with a 5/16" tap, so should be drilled to about 9/32".  A third hole should be drilled in the side of the block for a set screw for the motor shaft.

Tapping the 5/16" hole.

Tapping the set screw hole (I went with a 6-32 tap for this.)

Pictured above: the newly machined lever attached the the motor shaft.  To mount the motor I just used a steel bracket from a local hardware store.

With the oscillator finished, it was time to cut a bunch of steel rods.  8mm rods are ideal... I had some left over from 3D printer projects.  But in a pinch you can get away with 5/16" rods for this design... I ended up using a couple of these as well because I can buy them locally.

Above: first test of the oscillating mechanism.  Was a bit too dramatic for the application of agitating chemicals, so I ended up moving the 5/16th hole closer to the motor shaft hole.

The last thing to fabricate was the rubber "grippers" for holding the glass container steady in the agitator.  I used some scrap rubber tubing with foam rubber super glued around them.

The finished frame, with rubber grippers attached.

As you can see, the middle bar of the frame can be slid from side to side to accommodate various containers.

First footage of the finished agitator.  I wired a toggle switch to easily start and stop the machine.

I'll be using this quite a bit in the near future for a new project, so look forward to more images and footage of this guy in action!