4-inch to 3-inch Adapter for Spray Booth vent outlet

thingiverse

I've been eager to learn airbrushing on small models for quite some time now, so I acquired a spray booth that boasts a 4-inch vent hose to expel paint fumes outside. (Search on Master Airbrush Spray Booth) We have a bathroom in our basement that receives minimal use, so I set up the spray booth there and designed an adapter to connect the 4-inch hose to the 3-inch ceiling exhaust fan outlet which vents to the outside of the house. The adapter is composed of two pieces for effortless printing without support. I sanded the mating surfaces and bonded the two halves together with epoxy, allowing it to cure overnight. I removed the bathroom exhaust fan grill and then disassembled the motor/impeller unit so that the adapter could be installed. Since the exhaust fan housing is made of sheet steel, I added two 1-inch recessed areas to the adapter for gluing in some round magnets to support the weight of the adapter and hose. The 3-inch outlet on the housing was approximately 2mm below the top of the housing so I created areas for the magnets 2mm deep and utilized 4mm thick by 1-inch diameter ceramic magnets. These ceramic magnets proved strong enough to support the adapter - neodymium magnets would offer even better support. A thrust plate on the 4-inch section of the adapter allows for a piece of hard foam to be wedged in place to keep the 3-inch end of the adapter firmly against the outlet. The 4x6 inch hose that comes with the spray booth was not long enough for my needs, so I ordered a 10-foot dust collection hose from Harbor Freight. I used the rubber collar that came with the booth to attach the hose to the adapter and then employed a 4-inch hose clamp to attach the hose to the flange that attaches to the spray booth. It leaked some air around the hose clamp, so I also applied some duct tape there to seal it well. The 3-inch part of the adapter features a slot in it to accommodate a long screw that was used to secure the bathroom fan housing to the hose that goes to the outside. Your fan unit may have similar screws but likely in a different location. You could probably simply cut off the slotted portion of the adapter in your slicer before printing and it would function perfectly as long as your fan housing is 3-inch diameter. Some tape or silicone can be used to create a good seal where the adapter fits into the fan housing.