GUST is retired. Use its successor, Whirligig, instead!

TL;DR

GUST is a high-efficiency part-cooling fan shroud for the i3 family of printers, designed based on the results of my print cooling experiments. It meets five design criteria:

1. Dump as much cold air as possible, at the highest pressure possible, as close to the nozzle as possible. This improves the quality of short layers.
2. Do not trap hot air in the plastic deposition area. Push it away so that warping is reduced.
3. Allow easy access to the nozzle for bed levelling.
4. Provide a clear line of sight to the nozzle and an unobstructed view of the print-in-progress for filming time lapses (I recommend my super-compact bed-mounted Raspi cam).
5. Allow easy removal of the entire shroud assembly for access to the hot-end.

GUST is a work-in-progress, but it's ready to use right now! I suggest you 'Watch' this thing to get notifications about new revisions.

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Important compatibility info

Known to fit:

• Wanhao i3 Plus or rebadged versions
  • Stock hot-end/extruder
  • Micro Swiss all-metal hot-end
  • Does not fit Flexion hot-end/extruder (apparently the Flexion nozzle is too short?)
• Monoprice Maker Select V2.1 (thanks, Roykinn7!)

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This shroud is designed for a Wanhao i3 Plus, or a rebadged version of it. It fits onto an extruder bracket that has M3 holes shaped as slots spaced around 30 mm apart, on a tab that is 45 mm long.

There is a different kind of bracket that has holes (not slots) spaced 40 mm apart, on a tab that is 50 mm long. I have provided a slotted bracket to fit these measurements, but I can't guarantee that the other bracket dimensions are the same or that the shroud will fit your bracket's height.

I have also made the assumption that your nozzle is at least 6 mm tall from the heater block to the tip, which is the case for both the Plus' stock nozzle and also for the Micro Swiss all-metal hot-end's nozzle. GUST cannot fit into the space around a shorter nozzle, and cannot be made to fit there; it's already nearly too thin.

If you are able to use this shroud on a non-Plus model, could you please comment and let the community know? Info about your bracket and nozzle would be good.

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Bill of Materials

Note: Always use the latest revision of each STL (e.g. use Rev 2 instead of Rev 1). The newest files are always listed first, and they are always compatible with each other; you can use the Rev 2 duct with the Rev 1 shroud, for example, as long as they are the latest revisions of those objects. The old files remain 'below the fold' in case you want to explore them.

• 1× Cooling duct.stl. There is also a version with Meshmixer supports included, for those who don't have a slicer that can do custom supports.
• 1× Bracket.stl. The slotted bracket can fit on brackets with both 30 and 40 mm screw hole distances, and allows you to adjust the shroud along the X axis.
• (Optional) 1 mm shim.stl to raise the shroud above the tip of your nozzle. If you need a shim that is greater than 1 mm, use 10 mm shim.stl and tell the slicer to stop at the desired height. I use 3 mm of shim for my Micro Swiss hot end.
• 1× 50×50×15 mm blower fan. 24 V for Plus machines, 12 V for standard machines.
• 1× M4 screw (25 mm), washer, and nut.
• 2× M3 screw (12 mm), washers, and nuts. I bonded wingnuts to grub screws with Loctite, and I use thumb wheels to tighten them down. Tool-less shroud removal!

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Installation

1. Level your bed.
2. Join the blower fan, Duct, and Bracket using the M4 screw. Leave it loose for now.
3. Attach Bracket to the fan mounting bracket of the extruder block using the M3 screws. Leave these loose for now.
4. Looking from the side, align the nozzle with the opening of the shroud by moving the Bracket forwards or backwards. Tighten the M3 bracket screws.
5. If needed, add Shims to raise the base of the shroud about 1 mm above the tip of the nozzle.
6. Zero the Z axis. Pivot the Duct so that it is parallel to the bed. Confirm that it does not collide with the bed.
7. Tighten the M4 screw.
8. Suggested cooling profile: 0–20 % speed for the first layer. 100 % for all subsequent layers.

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Test spike slicer settings

Want to follow along? Here are the settings I used:

• PLA, 0.40 mm nozzle, 0.20 mm layer height.
• 2 perimeters with 2 bottom layers
• No infill
• 75 mm/s base printing speed
• Adjust printing speed for layers below 1 second, allow reduction down to 5 %

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Frequently Asked Questions

####Won't it melt from being so close to the nozzle?
Nope! My experience with shrouds like this is that so much cold air is passing through them that they barely deform, if at all. I have had this particular shroud printed in PLA and even touching the heater block's insulation and it isn't deformed.

If you are worried about the shroud melting while printing a large first layer without the fan running, there are four ways to deal with it:

1. Trust that PLA has bad thermal conductivity, and the design of the shroud means that only an island on the top surface of the shroud is being heated up, and the heat will find it difficult to spread to the rest of the shroud to cause a structural failure.
2. Increase the air gap between shroud and block.
3. Put extra insulation between the shroud and heating block.
4. Run the fan at a very low speed for the first layer (10-20 %) to keep air moving through it. Make sure to actually check that the fan turns at the speed you've selected; my fan won't turn for anything less than 20 % speed.

This was the best way to design the shroud as far as I could see, in order to meet the design requirement of getting right up against the nozzle. The nozzle is only 6 mm tall, so space is limited:

  | Heater block |
  ----------------
1 mm   |     | Insulating air gap
2 mm   |     | ===========
3 mm   |     | Air passage
4 mm   |     | Air passage
5 mm   |     | ===========
6 mm   \_____/ Clearance from print

There's no room, in short, and reducing the air passage just makes the fan louder and makes backflow worse.

####What kind of blower fan should I use?
The strongest one you can find with the highest static pressure rating. You can always turn it down if it's too powerful. I've had good times with Shenzhen Gdstime Technology Co. Ltd fans. I've also heard good things about YYQ fans, although I have never used one. But caveat emptor: CFM specs from random sellers are probably untrue.

####Can I use a 12 V fan in a 24 V system?
Yes, but you shouldn't. Aside from the possibility of the fans sparking because they're over-volted, they will eventually fail and start making these horrible grinding/rattling sounds.