Y-Axis Stepper and Einsy Trimec fan cooling duct for Prusa Box / Printer Box

The main goal of this model is to deal with random false Y-Axis crashes and layer shifts when printing in enclosure, particularly the Prusa Box / Printer Box. After some tests, I have tracked down the issue to the fact that crash detection is based on sensing resistance in the steppers, and sensitivity to resistance increases with temperature of the steppers. Consequently, printing in an enclosure makes steppers significantly more sensitive to things like any drag in the rails, U-turns in the print path, opening doors to the enclosure etc. What's more, crash detection is used to identify the home at the beginning of each print as well as when resuming a print after a crash. As a result, the location of the home would vary with the temperature of the stepper, sometimes by as much as 1mm for 10C of temperature increase. This results in shifted layers whenever the printer detects a “crash” and resumes the print. Y-Axis gets it the worst, since it sits under the hot bed and close to the PSU (at least in the Printer Box design).

https://forum.prusa3d.com/forum/original-prusa-i3-mk3s-mk3-hardware-firmware-and-software-help/y-axis-crashes/paged/2/#post-629068

This model builds up on Juanfra's original Einsy cooler design to also cool the Y-Axis stepper. For this, the model utilizes two fans. The mod keeps the stepper at about 35C and Einsy at 45C with the ambient temperature at 21C and enclosure at 37.5C. I've repeated my crash test and got 0 crashes in about 3 hours of printing at 150% of the speed, compared to 10 crashes within first 20 minutes before tuning belts, rails etc and 1-2 crashes in an hour with after tiding everything up.

https://www.printables.com/model/334251-an-object-for-testing-false-crash-detections-on-y-

Important:

This model is designed to work with rubber cylinder feet that come [optionally] with Prusa Box (https://www.printer-box.com/product/dampers-for-3d-printer/)  and also with some feet under the box to provide a clearance for the bottom fan:

• https://www.printables.com/model/249820-tapered-feet-raisers-with-rubber-bottoms-for-print

I'm also using this mount for the Y-Axis stepper, which puts the stepper about 1mm further from the frame compared to the stock mount.

Supplies:

1. Noctua 40x20mm fan Noctua NF-A4x20 (sits below the box). You can use a different fan, but would have to adjust the height of the fan's housing.
2. A Noctua NF-A4x10 40x10mm fan, bu you can use any 40x10mm fan of your choice.
3. Some shrink tubing and possibly 1/8" friction tubing.
4. M3x30-35mm to mount the 20mm fan.
5. M3x16mm bolts for the 10mm fan.
6. 7 of M3 1.8mm square nuts.
7. Optional - a fan controller https://www.amazon.com/gp/product/B07LBLWYZF/, 2 of M3x18mm bolts, and 4 8x3mm round magnets.

Printing instructions:

• The only part requiring supports is the stepper duct - see the images for the location of pain-on supports.
• Use “detect thin walls” and “detect bridging perimeters” in the slicer.
• Depending on your filament, the very top ("roof") of the stepper duct might be pulled together by the bridging filament cooling down. This would result in small overhangs on either side of the roof. They have no impact on functionality and can be trimmed away with a knife. Since the part is not structural in any way, a 5% fill should work just fine.
• Use the “Cut” feature in the Slicer to adjust the height of the 20mm fan housing if you are using a smaller fan.

Assembly instructions:

• Bolt the 10mm fan to the middle duct and route its cable though the opening in front of the duct.
• Insert the middle duct into vertical duct, making sure to not pinch the cable.
• Disassemble the 20mm fan's connector by pressing on the tabs with a needle and add an extra shrink tubing and/or friction sleeve to cover the exposed wires right next the fan. It is probably fine as it is, but it is nice to have for an extra piece of mind.
• Place the middle duct/vertical duct assembly over the vent hole in the box. Make sure to not pinch the cable.
• Place the 20mm fan in its housing, put the housing under the enclosure, route the fan's cable up through the opening and then through the cable hole in the vertical duct, and bolt the fan housing to the vertical duct. While bolting, make sure neither fan cable is pinched.
• Slide in the top vertical duct into the bottom vertical duct. Optionally, secure with a paper clip using the two holes.
• Carefully cut a zip tie that holds Y-axis and Z-axis stepper cables to the frame of the printer. You want the one closest to the Y-axis stepper. Reattach Z-axis cable with a new zip tie.
• Lift the back of the printer, place the stepper duct under the Y-axis stepper while routing the stepper's cable though the slot in the duct, and put the printer back down. The wall of the duct should be touching the back of the stepper. Don't worry about inserting the housing into the middle duct - we do it in the next step.
• Slide the stepper duct towards the middle duct and insert it fully.
• Route stepper's cable under the cable guide on the middle duct. You might need to lift the bracket slightly to help the cable go in.
• Slide the top cover through the slot in the stepper duct duct to seal of the holes.
• At this point, the ducts should be fully assembled. You can use some super glue to attach fan cable holders (remixed from here) to where you need them.

Fan controller

• Disassemble buzzer connector and add some extra shrink wrap close to the base of the buzzer. Gently bend buzzer's legs to the side and wrap its wires around the base of the buzzer.
• Insert the buzzer into the opening in the lid. You might need to rotate the buzzer a bit with some pliers in relation to its connector on the board so the wires are wrapped neatly.
• Attach some dielectric tape to the controller board under the buzzer to make sure the board is protected from buzzer's contacts.
• Bolt the lid to the base using two 18mm bolts.

More info on the controller can be found over here.