Voron Zero Top Hat Exhaust (Temp Controlled Fan)

Background

During longer prints and/or operation of my Formbot Voron 0.1 I had many issues with hot end heat creep causing print failure.    I started with a Dragon HF in the standard tool head before switching to the Bondtech LGX tool head.  Further I downgraded to a Dragon SF and finally downgraded further to a Dragonfly where I could use a 3010 fan.   I tried many fans of difference brands, changed the part fans not that it should have had any direct effect.  Tried different filaments, messed with settings and revisited the infamous Ellis guide.   

Finally it was a conversation with a super helpful Redditor that we came to the conclusion that the enclosure temperatures were just overcoming the hot end.   I was hitting mid 60s and had seen it as high as 70.   

Due to the location of the printer, propping the lid open was not an option and I couldn't just add a vent.  It needed to be filtered for the ABS fumes.   I also wanted a simple standalone solution that I could make without taking my Zero offline.  So this was when I designed the Zero Exhaust.

Of course there are many other potential solutions using the Pi GPIO, Macros and/or external PSUs. However, I liked the idea of a stand alone system that I could put together with parts I had lying around.

How it works

It uses an AZDelivery Arduino Nano powered from one of the Raspberry Pi USB ports.  The temperature is sensed by an Adafruit SHT31 Breakout because it was what I had lying around but other sensors would work of course (The Base Step File is included for mods).    There is a N-Channel Power MOSFET (IRLB8721) that switches on the ground and enables the 5v fan to take its power direct from Vin.  

Fans

You can use any 40mm fan.   My first experiment was with a 1.0A LED Fan which maybe gave around 4.95 CFM & 0.075 in/H20.   I later tried a 4020 Non-LED fan that at 0.14A gave just over 7.0 CFM & 0.135 in/H20.  You could use a 4010 Non-LED fan that at 0.14A would be around 6.12 CFM & 0.12 in/H20.  This data is based on GDSTime fans.

Materials Required

You will need:

• Arduino Nano.
• SHT31 or similar sensor.
• N-Channel Power MOSFET (IRLB8721) or similar.
• 40mm 5v Fan.
• M2.3 screws for fitting sensor.
• 6 x  M3x6x5 Heat Inserts.
• 4 x 6-8mm M3 bolts for the lid.
• 4 x 30mm M3 bolts with nuts for the fan.
• 2 x 6-8mm M3 bolts for mounting the Exhaust to the lid.
• Mesh (Stainless Woven 20 mesh).
• Nevermore Carbon - I use Nevermore as it is acid free and will not damage the printer.

Building

1. Print the base and optional inlet frame.   You don't need the inlet frame but it does make a good template for cutting the mesh and makes it look neat inside.  I use a little hot glue to hold the mesh and frame in place (see image).
2. Attach wires to your sensor and fit into place (see image).   
3. Attach wires to the Nano.  You can do this while the sensor is in place and this allows you to get the cable length just right (see image). 
4. Attach the 3 wires that go to the MOSFET and Fan to the Nano. 
5. Fit the Nano.  A little hot glue will hold it in place if required.
6. Solder the wires to the MOSFET with small pieces of heat shrink in place to cover the legs.   (see image)
7. Fit the the MOSFET. A little hot glue will hold it in place if required.
8. Prepare the lid mesh by making holes for the fan bolts.   The sharp end of a Scriber works quite well for this. Temporary use of M3 bolts will hold it in place as you do each hole and working over a fan allows the Scriber to penetrate deeper through the mesh making a larger hole.  (see image)
9. Fit the fan to the lid with the mesh making sure you get the cable run sorted.
10. Now you are pretty much ready to add the heat inserts (if you have not already done this), add carbon and put everything together.   

Mounting the Exhaust and Drilling your Voron Lid

There is a template to help in marking holes and drilling the lid.   I STRONGLY recommend removing the panel and drilling on a supported flat surface.

Programming the Arduino

To program the Arduino you will need access to the Arduino IDE.   Most of the variables you will need to adjust are at the top of the file and clearly documented.  I've included a simple test mode for simplicity.

During testing I have found that 35 degC is a good threshold temperature for printing ABS at 245/110.   You should conduct your own evaluation.