DIY Film Processor Project 3D-printed. Automatic lift, rinse pump and step-processor. Half-Eurobox size

[elgatosuizo]

This summer I completed my self-designed RA-4 film processor, and that was the ignition point for an older idea:
to build a small, semi-automatic rotary film processor in the spirit of the classic Jobo CPE/CPP series —
but 3D-printed, stepper-driven, and compact enough to fit in half a Eurobox (30 × 40 cm).

Originally, I discovered a nice build on Printables by @Franktion_442763 and thought I’d start from there.
But the STL files were difficult to modify (and used a DC motor, while I prefer steppers).
So I decided to redraw the entire design, and one idea led to another —
a motorized lift, automatic rinse control with a small pump, and a smart controller to orchestrate the process.
Eventually, I had moved completely away from the original model — except for the Eurobox footprint.
So, full credits to Franktion_442763 (and others who inspired DIY Jobo-style builds).

Design goals​

• Semi-automatic operation: automatic rotation, chemical dumping, and water rinse.
  (I skipped full automation with chemical pumps — too much cleaning afterward!)
• Compatibility: supports C-41, E-6, and B/W workflows.
• Heating: done via Sous-Vide immersion heaters, a proven and simple solution.
• Mechanics:
  • Stepper-driven drum rotation with three small gears centering the Jobo tank gear.
  • Stepper-driven lift with reduction gearing for torque.
  • Two-liter integrated rinse-water tank under the mechanism, thermally coupled to the main bath.
  • Three temperature sensors: one in the water bath, one in the rinse tank, and one handheld probe for chemicals.

Electronics​

After some early struggles (ESP32 was unstable with steppers + keypad),
I moved to an Arduino Mega 2560 Pro for control and a Nano dedicated to the steppers, linked via serial.
The flowmeter proved unreliable due to noise, so I now calculate volumes by calibrated pump time — works great.
Each component is isolated and filtered for reliability, and the firmware supports 7 process profiles with up to 12 steps each.

First test results​

The first full development cycles have run almost perfectly.
However, I’ve noticed a few small details to refine:

• The wide-mouth beakers I used aren’t ideal for temperature control.
  I’ve already drawn and 3D-printed three custom lids to improve chemical pre-heating in the water bath.
• The drain outlet drips slightly, so that needs a small redesign.
• The mantle bath can’t heat cold rinse water efficiently,
  but if you fill it already at the correct temperature, everything stays perfectly stable.
• To pre-warm developer and blix, I simply place their closed bottles in the water bath before pouring into the beakers.

Overall, the machine feels remarkably comfortable to use —
honestly beyond my expectations — and in terms of workflow and warm-up handling,
it’s surprisingly close to a real Jobo CPP.

Here some more Details on the mechanics:




I also recorded a demo video, which I’ll post soon.

 

[Bearman]

Amazing work! Looking forward to video and updates

 

[acrobatic_citron]

Looks great, although not wide enough it seems can it move the 3010? What would it cost to put together off the shelf? I do not own a 3d printer, UK based

 

[elgatosuizo]

Looks great, although not wide enough it seems can it move the 3010? What would it cost to put together off the shelf? I do not own a 3d printer, UK based

THe BOM is under 120€. I will publish the print files and instructions. I don't plan to sell it assembled or as kit. For moving a 2500 series or even 3010 it may can adaped to fit in a full Euro-Box. This version with 1/2 Box can only handle the 1500er series.