"Cold spot" on my heated bed?

[ciutateivissa]

Could the problem be caused by air coming off the extruder fan? Also, should the air pass over the extruder fan from the front of the printer to the rear, or vice versa?

Yeah, the extruder fan is ONE possibility. No mater from which direction the air comes, you should in any case prevent the print from any cool air. This was the reason I changed my hotend to a different type which needs no fan

Another reason could be, that a fan from the electronics (e.g. RAMPS or PSU) get sidetracked by the printer chassis and hit your print in this area. This was the case in my I3 as well, so I made a special box for my electronics where the fan is blowing in a direction away from the printer.

[old man emu]

The fan is the same size as the one supplied with the printer.

Maybe it is the heat bed temperatures I'm using. When printing with ABS, do we use 90 or higher for the heated bed?

OME

[Roxy]

Maybe it is the heat bed temperatures I'm using. When printing with ABS, do we use 90 or higher for the heated bed?

I print ABS at 110 C. But remember, that temperature is going to vary. In my case the thermistor is taped to the bottom side of the heater and the sides are sealed off. By the time the heat gets up to the surface of the glass, I suspect it is significantly cooler.

[ciutateivissa]

Maybe it is the heat bed temperatures I'm using. When printing with ABS, do we use 90 or higher for the heated bed?
OME

The heat temperature could even be higher, at last for the first three or four layers. I´m using 105° C for the first three layers, then reducing temperature to 96° C. It is quite important to get a consitant temperature over the whole heat bed so let the heat bed work at least for 10 to 15 min before your printing on it.

The fan is the same size as the one supplied with the printer.
OME

Ok, I understand. But maybe the new cooler is more effective (more rotations per min). I´m pretty sure that a smaller one would work much better, just give it a try... Disable the big one and use a 25 o 30 mm fan just for testing, you could just fix it with a tape, just to see what´s happening.

The fan schould just cool the tube of your hotend, not the nozzle itself.