Core One - Servo Driven Automatic Chamber Vent

This Mod adds a printer controlled servo to the chamber vent at the top of the printer. It will open and close the vent automatically depending on the filament you are printing. Being servo driven will ensure the vent will stay open if its needed and closed otherwise.

This mod uses a Sparkfun Servo Trigger to handle the two positions, open and closed vent,  of the Serve. It will also Supply the 5V power to the Servo as the GPIO board cant supply continuous power. The Sparkfun Servo Trigger is then controlled by the Prusa GPIO Board for the Core ONE, allowing us to control the chamber vent via g code now.

I have been testing this mode for a couple weeks now and it works very reliably for me. I have included some build instructions but they are not nearly as detailed as for example a the instructions that come with a Prusa kit. If you need help or have any questions you can message me or leave a comment.

UPDATE: 28.08.2025
I designed a magnetic pushrod connector allwoing you to more easily attach the servo pushrod to the nut of the chamber vent. This also makes removing the Top Cover a breeze as its now just held in place by a tiny bit of friction and a magnet. I recomend using my Top Cover Locks to hold your top cover in place with four easily removable magnets instead of the nylon rivets.

WARNING: This MOD is supplied as is and you build it at your own risk. I will NOT be responsible for any damage or injury to you or your property that may occur.  

Requiered Parts:

1x Prusa GPIO Board
1x GPIO Enclosure (Needs to be printed)
1x Sparkfun Servo Trigger
1x Servo Trigger Envlosure (Needs to be printed and is included in this mods print files)
1x Metal Gear Micro RC Servo
1x 600mm Servoextensioncable
26 x 6x3mm Magnets
1x 1mm x 180mm Stainless Steel Pushrod 
2x Female to Female Jumper Cable
10x M3x8 Screws
2x M3 Washers
2x M2x8 Screws
1x M2x6 Screw
1x Break Away Headers
1x 24v to 5v USB-C Power Transformer
1x Snapfit USB-C Port
3x M2 Heatset Inserts
1x PSU Cover Mount Mod (Needs to be printed)
1x Servo Mount (Needs to be printed and is included in this mod print files)
3x Magnetic Wire Mounts (Needs to be printed and is included in this mod print files)  


Assembly Instructions:

1. Buy and print all the required  parts
   IMPORTANT: During the printing of the Magnetic Pushrod Connector the print needs to be stopped at the right moment and a magnet inserted into the print. This is not possible after the fact. The 3MF file has a pause already setup at the right moment.
2. Take off the PSU cover and attach the power transformer to the newly printed PSU cover.
3. Wire the power transformer into the PSU.
4. Screw in the new PSU cover with the two original screws.
5. Cut to length and solder the break away headers to the GPIO board and the Sparkfun Servo Trigger board.
6. Solder the USB-C Port to the power input of the Sparkfun Servo Trigger (See Wiring Diagram)
7. Put both boards into their printed housings and secure them with the 8 M3x8 screws.
8. Add the 10 required magnets to the two housings. 
9. Add the 6 magnets to the little cable mount pieces.
10. Add the 10 reuiered magnets to the servo mount. IMPORTANT: There is a smaller round hole right behind the servo. This is a cutout a nylon rivet that sticks out from the side wall. DO NOT try to force a magnet in there!
11. Add the two M2 heatset inserts into servo mount.
12. Attach the servo to the mount with the two M2x8 stews. Thread the servo wires though the hole in the Servo mount and along the cable Chanel on its backside.
13. Attach the servo horn that came with the servo to its top gear and fixate it with the supplied screw
14. Insert the 180mm pushrod into thetiny 1mm hole on the side of the Magnetic Pushrod Connector
15. Insert the M2 Heatset insert into the 3mm hole on the frontside of the Magnetic Pushrod Connector and screw in a M2x8 screw half way.
16. Attach the push rod to the servo arm and install the servo mount. See images.
17. Attach the Magnetic Pushrod Connector to the closest nut of the chamber vent
18. Attach the Sparkfun Servo Trigger to the servo (Be careful to plug it in the right way. There are small dots on the enclosure to mark were the Ground Pins are!) 
19. Plug in a 5V USB-C powersupply into the Servo Trigger. IMPORTANT: Only a “dumb” powersupply will work as there is no logic to negotiate power delivery on the board or the connector)
20. Once the Servo Trigger is powered on, use an appropriate small screwdriver to adjust the potentiometer (Hole Marked “A” on the Sparfun Servo Trigger Enclosure)  so the servo arm just closes the vent.
21. Bridge the two input Pins (the ones in the wiring diagram that are connected to the GPIO board) with a jumper cable.
22. Now adjust the pot in hole “B” to move the servo arm that the vent is fully open.
23. The pot in hole “T" determines the speed the servo will transition between the open and closed state.
24. Remove all cables from the Servo Trigger and attach the 600mm extension cable and route it under the xy gantry to the back of the printer. (see picture)
25. Affix the servo extension cable to the side of the printer with the provided magnetic cable mounts.
26. Attach the Servo Trigger to the back of the printer and attach the cables according to the wiring diagram.
27. Last step is to add the supplied G-Code to the printer profile in Prusa slicer.

GCODE that needs to be added to the "Start G-Code" Section in Prusa Slicer :

;
;Automatic Chamber Vent Control
;
{if filament_type[initial_tool] =~ /.*(PLA|PETG).*/}
M262 P0 B0
M264 P0 B1
{else}
M262 P0 B0
M264 P0 B0
{endif}

I recommend adding it right after the G28 (home all) command.


GCODE that needs to be added to the "End G-Code" Section in Prusa Slicer :

; 
; Auto close the vent if it was opened
;
{if filament_type[initial_tool] =~ /.*(PLA|PETG).*/}
M264 P0 B0
{endif}