I noticed some problems with bridges and at the fore of the benchy when testing my ender.
So I looked for a duct. I had some standard fans here, but just one design, attached to the original printhead used one. And this one didn´t work for me.
So I decided to make my own.
This fan duct is mounted magnetically to the original printhead to allow to remove it any time without tools. So, for example the laser can still be attached without effort.
BEFORE you print this one: My issues with benchy were allmost solved, when I finaly replaced the original fan (24 V) in the tin-housing of the printer with a new one. The principle of the fan cooling the heatbreak and blowing down as well isn´t that bad.
I removed previous versions of my fan since the one with the bigger and rounded outlet has less resistence to the airflow. This one leads to the most improvements in print, as shown in the pictures.
Print it with „support touching printbed“.
In addition you need
40 mm fan - preferably 24 V
2 neodymium-magnets 10 mm in diameter and 3 mm thick
2 to 4 screws for the fan
a plug connector for the 12V or 24 V (i.e. 2 wire JST battery-plug)
wire with a connector (eventually mounted at the fan) to the controller-board
Depending on your fan can use the 24 V on the ender-4 Board (some use it for the LEDs) or the 12 V right under the plug that is labeled "laser" - this one is controlled by marlin (2.0 the version I use) too.