Kobra S1 Fan Duct with LED Lighting

I wanted more light, especially to see that first few layers at the print head.  I created a new duct with mounting for a strip of LEDs. If you made my ACE Pro lighting upgrade, you’ll already have the LEDs needed.  There are plenty of ways you can do this project, so feel free to do something different.

Parts List

• New Fan Duct (printed)
• LED Cover (printed)
• M2.3 x 5mm flat head self tapping screw – I bought this kit of screws for various projects including this one: https://www.amazon.com/dp/B0D12MDPRL
• LED 24V COB strip 20mm long x 5 mm wide, 4000K (cut at the marks on the strip) https://www.amazon.com/dp/B0CWV93XZN
• Package of 2-pin JST ZH 1.5mm connectors (male and female), with 150 mm wires https://www.amazon.com/dp/B0B58M7D49
• Package of 2-pin JST GH 1.25 mm connectors (male and female), with 80 mm wires   https://www.amazon.com/dp/B013JRWCBU
• 2mm diameter heat shrink tubing

Printing Parts

Print the new duct in PTEG or ABS. We used transparent blue PETG. PLA is not recommended as it will deform under heat.  If you use very high bed temperatures, you may need to use a different filament designed to resist higher temperatures.

We did tests at 15% and 30% fill (very little difference) and tests at 0.12 mm layers and 0.20 mm layers, and again there was very little difference in quality.  Note that the tree supports were a pain to remove, and worse with 0.12 mm layers.  We did some tweaking of the support settings, but didn’t find a great fix. Final print was 15% @ .20 mm layers, tree supports.

Print the LED cover. We used clear PETG, with 100% Infill, 0.20 mm layer height, and normal supports.  White PETG will likely work as well if you don’t have clear.

When working with transparent filaments, you typically get the best results at the higher end of the recommended temperatures and running at a slower printing speed.

 

Printer Preparation

If the bed is not lowered about halfway, on the Printer, go to Settings -> Move.  Select Home. When complete, you can lower the Z+.  I recommend going down about 100mm.  

While you can have the printer powered while doing the rest of the work, do not attempt to home the printer with the front cover off!

Duct Wiring and LED Installation

Remove the front print head cover.  Remove the two screws holding the orange duct and remove the orange duct carefully sliding it up off the post and then out.  Nothing needs to be forced.

Using the female JST ZH connector with 150 mm long wires tin the two leads. Feed the connector wires through the hole in our new fan duct.  On the LED strip, remove a portion of the backing where it shows the polarity. Further, remove the clear adhesive from the two copper solder pads.  Tin the pads. Bend the wire ends 90 degrees and connect the wires facing to the center of the strip (see photo). The red connects to the +24V and the black to the minus.  Cut any excess wire that goes beyond the LED strip.

Remove the LED backing and attach to the slot.  It will be about 1mm from the nearby perpendicular edge, so the cover fits. Attach the cover with a M2.3 x 4 mm long self-tapping screw. The cover is optional, but we are concerned the LED strip’s adhesive might fail under the high heat conditions and drop into the printing causing no end of issues.

Dress the wires to the side as shown, so they don’t encounter the hotend’s heatsink.  Tighten the two screws holding the duct in. Avoid overtightening these screws!

Power from Hotend Fan

This fan is on whenever printing active and is on at 100% power (24V).  There are likely other power sources. 

We tried the model fan (in the front cover) for power, but it proved to be a poor choice. The model fan is off for the first 3 or so layers. When the model fan is on, it may be under 100%, causing the LED to not light, be dim or flicker. 

Cable Assembly

Have ready two 2 mm diameter x 10 mm long heat shrink tubes.  Then cut, trim and tin the following wires:

• JST GH 1.25 mm male connector, cut wires to 20 mm
• JST GH 1.25 mm female connector, cut wires to 20 mm

Insert the heat shrink tubing over each of the 20 mm long male wires and solder the JST GH male and female wires together as shown to the 150 mm long JST ZH male connector. Important: the premade JST GH connectors are backwards – where the black wire is 24V and the red wire is ground! Be sure to connect the long 150 mm ZH connector wires BACKWARDS!  See our photo.  Move the heat shrink tubing over the soldered joints and shrink the tubing.

Final Assembly

Remove the rear cover (four T20 screws).  Remove the F1 hotend fan connector from the PCB. Insert the male short cable into this connector. Connect the hotend fan to the cable’s short female connector. Carefully dress the 150 mm cable with the other wires over the top and down the front like the model fan’s wires.  You want it to go under one of the two black plastic clips at the top so it will not interfere with the rear or front covers.

Install the rear cover and insert the 4 screws.  Do not overtighten these screws to avoid cracking the plastic. A light touch is required.

With the front cover, attach the model fan (all black wires) to its mated connector. Connect the LED red/black wired connectors together.

Press the front cover into place.

Testing

On the printer’s menu, you can change the hotend temperature.  Enter a value one degree higher than the current temperature, and the LED should light up.

Weight

In our design, the new duct is lighter than the original, and with the LEDs and wiring, it is only 1 gram heavier than the original without LEDs.  The total for the new duct, front cover and fan is about 82 grams. Since the weight did change slightly, we recommend doing a new Resonance compensation on the next print.

Final Notes

Do not use a power screwdriver. Hand tighten all the screws related to this project, and be careful not to overtighten, or you may crack the plastic.  The LEDs consume about 7 mA, a trivial amount.