MK4 Bi-Directional Fan Duct - Lightweight and Effective
Description
PDF*NOTICE*
If your duct is not centered to the nozzle, please print the offset version of the duct that offsets the ducts 2mm to the right to try and correct for this. There does not seem to be a reliable pattern for what machines need the offset version.
Description
After some issues with cooling the opposite side of the cooling fan duct, I designed this new fan duct that allows air to be directed onto the print from both sides while still allowing the duct to be swung away from the nozzle in the same manner as the stock shroud while remaining as light as possible. While this duct takes up a larger footprint than other designs, it is actually slightly lighter than any other multi-directional fan duct I have found on Printables with a standard weight in ASA of 7.75g versus the 8g+ weight of the other popular designs.
See the includes pictures to show examples of improved performance with PLA using the same GCODE with the stock duct and the new duct. The original fan shroud sees corner curling at overhangs on the opposing side of the cooling fan. This effect is a problem at as low as 45 degrees. With the new duct, overhanging corners are cooled evenly at all angles with great performance up to 55 degrees of corner overhang. Also, bridging shows less sagging over longer lengths with the example showing a 50mm bridge printed with the stock duct and the new duct.
Also included is a test print to show overhanging performance at different angles. I recommend printing this before and after your new duct has been installed to verify that more even cooling performance has been achieved.
Compatibility
- Works best with this fan door that helps align the vents to the nozzle properly:
- Designed for Prusa MK4 printheads
- Works with silicone sock attached to nozzle
- Works with hinged fan door for nozzle access
- Works with hotend fan draft shields - a low-profile shield I designed is linked below
Print Parameters
- Make sure you grab the correct model
- If the nozzle isn't aligned to the vents, you may have to print the other model
- Unfortunately there doesn't seem to be a rhyme or reason for why some printers have the nozzle offset
- Print in ABS/ASA or another temperature resistance material for the longest service life and for lighter weight
- For 0.4 nozzle - Use 0.15mm STRUCTURAL stock profile
- For 0.6 nozzle - Use 0.20mm STRUCTURAL stock profile
Installation
Optional but HIGHLY RECOMMENDED: Install a new fan door to help center the vents to the nozzle. Use this model: Revised Prusa MK4 Fan Door - perpendicular to X-axis by Mike81622 | Download free STL model | Printables.com
Carefully break off the custom bridge supports between the two vents and clean up any uneven surfaces on the edges of the vents with a razor blade.
Remove the two screws connecting the existing fan duct and use the same two screws to attach this one.
Do not overtighten - the threads are only plastic and can strip
Feedback
This is actively being worked on and improved, so please give feedback to assist in the design work. I only have one Mk4 to go off of and depend on information from the community to determine if there are any alignment issues or performance issues.
Changelog
V1.0
- Initial Release
V1.1
- Added internal bridge to improve poor bridging characteristics on the top of the far vent
V2.0
- Major redesign of the duct
- Added an alignment plate that snaps to the hotend fan housing to act as protection from fan turbulence and as a way to align the vents to the nozzle
- Changed vent geometry to better clear silicone socks
- Added more material to the top of the vent to keep it from sagging over time from thermal saturation
- Added version information to the fan duct
V2.1
- Inclusion of Alignment Tool to allow end user to determine nozzle position in relation to the hotend fan housing
- Breakup of the model into three variations, A, B, and C, that correspond to the markings on the Alignment Tool
- Added material behind the alignment plate to make chamfer more consistent
- Slightly changed geometry of alignment plate to make the duct sit more horizontally and clip into place more snug
- Moved version info to new location and added variation info to each model
V2.2
- Redesign of exhaust vent geometry to further even out cooling performance across all angles of the print
- Retired the alignment tool as the new geometry is far more forgiving for nozzle placement than the previous design
- Slightly loosing snap-on mechanics to lessen strain on hinge when closing fan duct
- Added custom supports to ensure consistency of exhaust vent overhangs
- Added an “S” version of the duct to work with a purpose-built draft shield of my own design, and a remix of a popular design
V3.0
- Exhaust vent geometry completely reworked to increase airflow velocity
- Internal surfaces smoothed out to help improve airflow through to the far duct in particular
- Removal of the alignment plate as it was determined to be no longer necessary
- Fixed issue with vent scraping hotend with silicone sock attached
- Rounded most hard edges on the exterior of the model
V3.1
- Internal bridging improved drastically with stepped bridging through the entire duct
- Wall geometry changed to allow printing with either a 0.4 or 0.6 nozzle
- Significant weight reduction to 7.75g when printed with ASA
- Chamfering on bottom surfaces to help with elephant's foot
- Vent overhangs improved to reduce post-processing
V3.2
- Very minor change to vent alignment to center vents to nozzle
- Thicker bottom surface
- Internal chamfers added to aid in layer adhesion of bottom layers
Tags
Model origin
The author marked this model as their own original creation.
