Spiral ducting hose cuff 50mm

This is for 50mm inner diameter spiral hose (aka convoluted hose, or flexible ducting hose), the kind typically used in a workshop for dust extraction (although often it's larger diameter in a workshop). I find that for short runs, 50mm is great for fume extraction from a printer enclosure as you don't need (or want) a huge amount of airflow, so typical 100mm/4" duct is overkill. I'm also working on some other 50mm accessories, including a window or wall mount external vent with anti-wind-blowback - I'll post those once properly tested in real use. I'm using a typical 120mm DC fan, which can push a decent amount of air over a short run (eg, 2-4 metres).

Search (eg, ebay) for “pu flexible ducting hose”.

Clockwise or Counter-clockwise?

Look at the cut end of your hose. Starting at the cut end of the spiral wire, which way does the wire go? If it moves clockwise away from the cut, you need the clockwise model. If it moves counter-clockwise away from the cut, you need the counter-clockwise model. Somewhat counterintuitively (at least for me), you will have same direction on both ends of the hose.

Counter-clockwise

Clockwise

Dimensions

This model was designed for the hose that I have, which has the following nominal characteristics:

• Inner diameter: 50mm
• Outer diameter (widest): 58mm
• Spiral wire diameter: 1.4mm
• Pitch: 14mm
• Thickness of single wall: 0.45mm (note, the wall material is doubled up in places due to the construction of the hose, this measurement is for the single thickness).

There are two complete rotations in the “threaded” section of the model, and 20mm length of the straight section, which also has 50mm inner diameter. My original Fusion 360 model tries to be parametric, but working with coils in F360 can be quite a nightmare, and I had several nasty crashes and hangs to work around. Some aspects just can't be made properly parametric due to F360 limitations (notably the terminus of the thread, where it smoothly blends into the straight section). If there is demand for other sizes, I'll see what I can do.

Printing

You are strongly advised to use the supplied gcode, or your own from the supplied 3MF files with PrusaSlicer, as the settings are customized to suit the model and the material.

Print with a sturdy TPU. I used Flexfill 98A (Traffic Black in the picture). Vase mode, 0.4mm nozzle, 0.2mm layer height, 0.8mm layer width (yes, 0.8mm), no elephant foot compensation. The model is sized for 0.8mm wall thickness. These settings produce a very nice print that's also very tough, with a decent wall thickness and excellent layer adhesion.

Fitting

Make sure the cut end of the spiral wire is not sticking out - bend it slightly inwards (ie, towards the centreline of the hose) so that it won't catch on the cuff. Use a little silicone spray lubricant on the inside of the threaded section of the cuff, then carefully “screw” the cuff onto the hose. It should be a satisfyingly snug fit, if your hose has the same dimensions as mine. If the join is not sufficiently airtight, you could try using some silicone sealant on the outside of the hose before joining, or perhaps some silicone grease (I've not tried these ideas yet).

If the straight section is a bit snug to go over your 50mm outer diameter fitting, you can stretch it a bit with your fingers.