Paterson System 4 motorized stirrer

This system assists with easy and consistent film development by enabling automatic agitation in a Paterson System 4 developing tank.

It is sized for a NEMA-17 type stepper motor. I drive my motor with an Arduino microcontroller and EasyDriver stepper driver.

This system should not be inverted, as is conventionally done during film processing. Liquids would get into the drive motor. 

I use a nearly continuous reversing agitation cycle with acceleration and deceleration at each end, peak speed approx 60 rpm. Most sources on the internet suggest reducing development times by something like 10-15% when using continuous agitation compared to conventional intermittent agitation. When placing the motor mount onto the tank after pouring in the chemicals I recommend having the motor running. This permits easy engagement of the drive slot on the rotor with the tabs on the reel central spindle.

I personally prefer longer developing times in dilute chemicals as this reduces concerns about accurate timing.

The driveshaft hole in the rotor is sized for a 5mm shaft with a flat. As printed by my printer with ABS filament this requires an oversized hole. So 5.4mm. My printer may be overextruding or something. If this does not work for your printer I suppose you could scale it in the XY plane or some such workaround.

Also, expect the film development purists to tell you that you will be going to hell for sure, due to not doing intermittent agitation with inversions every so many seconds.