Histology Tissue Processor

1.   I have made a processing station out of wood with 5 bottles, 5 servos, and a magnetic mixer.  Magnetic mixer works well.

2.  Change of plan for the pinch valves.  I decided to use fewer and smaller 3D printed parts.  Printing big parts is slow,  making changes tedious, so I moved to make more use of wood and aluminium.   The servos are screwed to a wooden bar.  An aluminium bar is fixed beside the servo as "anvil" for  the cam to press against.  I will probably just use polymorph to hold the silicone hoses in place.

The servo horn has been changed from a helical cam to a straight horn. 

3.  3D printed joiners.   I only have 1m of 6mm od, 4mm id silicone tube and think I will need about 3-4m.  The tubing is fairly expensive to buy in Australia and very slow to bring in from China so I am only going to use silicone tubing in the pinch valve  and use clear vinyl tubing elsewhere.  This will not affect function.  All silicone tubing would be cleaner and more aesthetic.  I order to to this I printed 10 joiners to connect the vinyl to silicone.

3. Second air pump did not work.  I had ordered a second air pump a while ago from China.  Sadly it did not work,  (being open circuit)  so I did a destructive autopsy.  The problem seemed to be the  flimsy metal coated plastic brushes.   Another one ordered (bit more expensive this time).

4.   Servo connector.  I made a "dead bug" style servo connector for 8 servos.  For the  power leads I   soldered a thin wire along a row of 9 pins (two rows).  For the control leads I joined two rows of 8 pins by thin wire,  then glued all 4 rows together with epoxy.  I soldered a row of 8 female headers to some rainbow cable for the connector for the Arduino 2560 Mega.  This is compact, seems strong and tests out OK with a multimeter.  

Next:  

 Test new servo valves.

Test sero connector.

A magnetic flea is a rod about 30-40mm long which is placed at the bottom of a container to mix fluids.  The flea is magnetic and is rotated by an external magnet.

A placed a small neodynium magnet on each end of an 8mm steel rod to make a bar magnet.  This is enclosed in a 3D printed plastic case with central ridge to facilitate rotation.    I glued the two halves of the case and covered it in expoxy because some of the chemicals  in the retort are noxious and the 3d print seemed slightly porous.  The flea is dropped in the bottom of the retort.

 An openscad sketch of the case is provided.  It would be easy enough to make a non-3d printed version.

The motor is a geared robotic wheel motor held down by a zip tie.  I cut a steel rod to the same size as the one in my flea and put a magnet on each end then drilled a small hole in the centre which I glued over the axle of the motor.  This made a rotating bar magnet which I placed under my retort.

Testing of the system was successful.

Initial log entry covering progress so far.

1.  Working 3d pinch valve.  The valve (see openscad file) works but I will tinker a bit more before the final version.  Valve just tested  by blowing.

2.  Tested air pumps to move fluid.  Works well.  (Automated pinch valve not used in this setup).  Only have one air pump.  Second one ordered.

3.  Tested Arduino Mega with firmata and Johhny five. Works well,   controlling LEDs to mimic heaters and mixers.  Pyfirmata works but prefer interactive Johhny Five while prototyping. 

4.  Tested magnetic flea with  motor to drive magnet.    Flea in water in plastic bottle.  Works well.

Most individual components work.  

Next stage is to prototype a complete module with movement of chemicals and mixing.