MK4 Bi-Directional Fan Duct - Lightweight and Effective

prusaprinters

*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. DescriptionAfter 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.  CompatibilityWorks best with this fan door that helps align the vents to the nozzle properly:Revised Prusa MK4 Fan Door - perpendicular to X-axis by Mike81622 | Download free STL model | Printables.comDesigned for Prusa MK4 printheadsWorks with silicone sock attached to nozzleWorks with hinged fan door for nozzle accessWorks with hotend fan draft shields - a low-profile shield I designed is linked belowLow-Profile Design: https://www.printables.com/model/607780-mk4-low-profile-hotend-fan-draft-shield-compatible Print ParametersMake sure you grab the correct modelIf the nozzle isn't aligned to the vents, you may have to print the other modelUnfortunately there doesn't seem to be a rhyme or reason for why some printers have the nozzle offsetPrint in ABS/ASA or another temperature resistance material for the longest service life and for lighter weightFor 0.4 nozzle - Use 0.15mm STRUCTURAL stock profileFor 0.6 nozzle - Use 0.20mm STRUCTURAL stock profile InstallationOptional 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.comCarefully 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 FeedbackThis 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. ChangelogV1.0Initial ReleaseV1.1Added internal bridge to improve poor bridging characteristics on the top of the far ventV2.0Major redesign of the ductAdded 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 nozzleChanged vent geometry to better clear silicone socksAdded more material to the top of the vent to keep it from sagging over time from thermal saturationAdded version information to the fan ductV2.1Inclusion of Alignment Tool to allow end user to determine nozzle position in relation to the hotend fan housingBreakup of the model into three variations, A, B, and C, that correspond to the markings on the Alignment ToolAdded material behind the alignment plate to make chamfer more consistentSlightly changed geometry of alignment plate to make the duct sit more horizontally and clip into place more snugMoved version info to new location and added variation info to each modelV2.2Redesign of exhaust vent geometry to further even out cooling performance across all angles of the printRetired the alignment tool as the new geometry is far more forgiving for nozzle placement than the previous designSlightly loosing snap-on mechanics to lessen strain on hinge when closing fan ductAdded custom supports to ensure consistency of exhaust vent overhangsAdded an “S” version of the duct to work with a purpose-built draft shield of my own design, and a remix of a popular designV3.0Exhaust vent geometry completely reworked to increase airflow velocityInternal surfaces smoothed out to help improve airflow through to the far duct in particularRemoval of the alignment plate as it was determined to be no longer necessaryFixed issue with vent scraping hotend with silicone sock attachedRounded most hard edges on the exterior of the modelV3.1Internal bridging improved drastically with stepped bridging through the entire ductWall geometry changed to allow printing with either a 0.4 or 0.6 nozzleSignificant weight reduction to 7.75g when printed with ASAChamfering on bottom surfaces to help with elephant's footVent overhangs improved to reduce post-processingV3.2Very minor change to vent alignment to center vents to nozzleThicker bottom surfaceInternal chamfers added to aid in layer adhesion of bottom layers