Like many here, I was having significant difficulty in getting reliable prints in PLA, due to filament jamming caused by heat creep. After much consultation with others on this forum, and lots of experimentation on my own, I have concluded that the stock miniature blowers are just not adequate. The following upgrade appears to have completely solved my PLA heat creep issue.
I located a 20mm 5V fan that has nearly three times the airflow of the stock blower:
I designed a shroud to concentrate the airflow on the heat block. I also designed a mounting clip, making it reversible to allow some flexibility in the mounting location. I printed both of these parts in ABS, and here’s what they look like, along with the fan:
The holes in face of the shroud are sized to be tapped for 2-56 screws.
I added a layer of copper foil on the surface nearest the heater block, just for good measure:
Here’s how I have them installed on my Dual Head V2:
I replaced one of the extruder bolts, the one underneath the stepper motor, using an M4 x 35mm machine screw with a 7mm hex head. This also solves the annoying problem of trying to hold the extruder mounting nut in place during reassembly. Underneath the fan mounting clip is a 6mm tall spacer with a 4mm clearance hole. The screw comes down through the spacer, through the clip, and another nut goes on the end to hold it all together and hold the extruder down. I printed the clip at 100% infill so that it could withstand the force needed for that task.
I had originally intended to place the fans both on the same side of the head, which is why I made the clip reversible. However, I found that it works better for me as shown, with the fans diagonally opposed, mainly because in these locations the shrouds don’t interfere with the thermistor wires. In light of this, the clip could be re-designed to make it non-reversible, and extended to eliminate the need for the through-hole spacer. I may get to that…
Everything just barely fits, with very little room to spare! I have not tried, but I believe this design may also work on the single head.
There is about a 2mm gap between the bottom of the shroud (copper foil side) and the top of the heater block. There is no sign of the shrouds melting or discoloring as of yet, after many hours of printing PLA at 205C with a 60C bed. I still need to do a “torture test”, setting the nozzles to 240C and the bed to 110C and lowering the head down to the bed and just letting it sit. Hopefully the shrouds will withstand this.
Here’s the whole thing put back together:
I have attached STL files for both parts.
Clip 2016-04-19 01.stl (25.3 KB)
Shroud 2016-04-19 01.stl (80.4 KB)