[DIY] Automatic Fan Door / Blast Gate - 3D Print

Needing a wall-mounted fan with an automatically opening / closing door for the camper van, the search was on for such a device. That came out empty though, which led to designing the custom 3D printed fan-holding blast gate devices above.

Made 2 versions: a small bare one (right in pic above), and a completely covered version for the 'garage' area inside the van next to the rear doors.

Design files link at the end, below. For a 92mm fan, but might publish later the 100mm & 120mm versions as well. If spare time suddenly materializes out of nowhere... Yeah, right 😂

Happy printing to all !

 

Overview

There's a plethora of blast gate types out there, especially for dust collection via 4" pipes: iris, butterfly, ball valve, guillotine, etc. Alas, most of them are either too expensive, or too big for a van, or require a micro-controller for the servo / motor, or use a too-jerky solenoid, or count on gravity to close the door back down...

Disappointing. Need an affordable 12V 92mm fan holder with a simple sliding door, low profile, reasonable width / height, and no complex electronics.

A somewhat simple hack could consist in using an existing blast gate for dust collection (Home Depot examples: plastic, aluminum) and graft on it some form of motion device for the door:

But they are not really designed to be mounted flush on a wall, nor do they have provision for holding a fan or a cover, and mounting an actuator would require a few tricks.

 

Custom Blast Gate

All that can be solved by 3D printing a custom fan holder with a sliding door. So it totally had nothing to do with feeling like playing with Addi(c)tive Manufacturing, I swear !

The motion can simply be accomplished with a 100mm (4") 12V actuator. Those already have integrated limit switches to automatically stop at the start & end of their range.

The user just has to toggle a 2-position permanent DPDT switch to start the fan (door opens) or stop it (door closes). And a simple diode in series with the fan powers it when the actuator is extended, while preventing feeding it a negative voltage when the switch is in the "User-wants-OFF" position (i.e. inverted polarity, which makes the actuator retract and then stop).

Fritzing diagram:

The diode used here is an SR540 (Schottky, 40V, Vf 0.55V, If 5A). Many other diodes could be used though. Their If just needs to be at least ~2A since the actuator barely uses any current and since small 12V fans rarely get close to 1A.

Finally, a local fuse protects the cabling that is routed inside the van's walls and coming from the switch. Kind of the opposite of this one 😂:

 

Mini Holder

The holder consists of 3 parts, Front / Back / Outlet, that are glued together:

 

The outlet's outer diameter is 4" (10cm). But this part can easily be modified to match other pipe diameters.

 

The parts were printed with ASA filament to resist ~120°F (50°C) summer temps inside a Ford Transit camper van.

Warping was initially very bad. Took 2 weeks to refine the print settings and the chamber heating / cooling process. Details below(*). Anyhoo, finally, reasonably flat and dimensionally accurate parts:

Glueing started with Front + Back thanks to the self-aligning groove & tongue designed into them. Last is the outlet, rotated such that its 2 inner bumps match the ones on the Back part.

The electrical components were simply soldered on an Adafruit half-sized perma-proto breadboard. Finally, the actuator was installed with a couple of M4 25mm flat head machine screws.

Completed assembly:

Applying 12V to the power input terminals got the fan spinning and the door whizzing:

And, of course, reversing polarity stopped the fan and closed the door. Sweet 😄

Fully Covered Version

This version is designed for a 25mm thick fan. Supporting a 38mm fan can be done by tweaking the model of the Cover Top part to make it bulkier.

This holder is too long to fit on the 256x256mm printer bed, so some parts were split in half, with proper matching surfaces for a strong glued joint. The joints are also all staggered across the 3 assembly layers (back, mid, front) so as to make for a stronger glued assembly.

The Back Top & Bottom are first. Next are the 2 small rectangle Bars, followed by the Front Top and the Front Bottom.

Once the base is ready, it is used as a support to help glue the Cover Top and Bottom parts together. That ensures that the edges of the cover close properly against the base's shape, and that the cover assembly's length fits snuggly prior to installing the magnets.

The cover holds in place thanks to an inside lip at the top, and six 8x2mm magnets at the bottom:

The actuator is secured with a 20mm flat head M4 screw at the top, 25mm at the bottom. Glueing the pipe Outlet, and installing the electricals and the fan, completes the build:

Ready for installation in the van. C'est parti !

Add pic once installed in the van.
Sorry, got down to -20oF (-28oC) weather lately.
Have not been able to work on the van for the last month 😅

 Need to find me more stuff to 3D print, that was a fun project...

 

Design Files

Both the F3D and STEP files are posted on Github

Feel free to copy, hack, remix, or to let me know if there are questions. 

 

Meanwhile, it's now time to design a proper chamber heater for the P1S. Herehence starts another '3D printing should-just-be-a-tool-but-is-not-there-yet' quest... 😂

(*) Settings for Elegoo ASA on a Bambu Lab P1S, 0.4mm nozzle:

• PEI textured plate, Bambu's liquid glue stick, insulation blanket on and around the printer, fans OFF
• Preheating with bed at 100°C + heat gun pushing 280°F (140°C) air at slow speed at the top of the printer until the chamber reaches ~55°C (takes about 30' @ 50°F / 10°C ambient)
• 1 part at a time on the bed, no cramming of the space as the part corners lift if anywhere close to the edges of the bed
• All speeds capped to 150mm/s max, and accelerations to 1000mm/s2 max, to avoid overcooking the belts & stepper motors (the heat gun creates hot spots. Will replace soon with a chamber heater+fan lid)
  
• Printing temps: 270°C nozzle, 100°C bed, heat gun ON
  
• Slicer: 0.93 flow, 10mm3/s, 0.2 / 0.45 layer height / width, 3 walls, 3 top & bottom layers, 35% adaptive cubic sparse infill, 2% infill / wall overlap, 12mm outer + inner brim
  
• Support necessary only on the door of the 'covered' version, on the underside of the actuator mount
• 30' cooldown at the end with heat gun ON, bed OFF
• 30' cooldown with both gun & bed OFF
  
• Pop off the parts, then 5' of bed reheat at 100°C to peel away the brims

Yep, it was a nightmare to get to that point. Almost 1Kg of filament just for filament tuning and warping tests over 2 weeks. Followed by excruciatingly slow 2 to 3 hour prints + 1.5 hour of preheat & cooldown for each part which took another 2 weeks...

Note though that printing these parts with Bambu Lab's PLA was a breeze. Just default settings, bed crammed with parts, 45' prints, no warping. Love PLA 😍  Really need someone to invent a high-temp-no-warp high speed PLA variant !