Nozzle keeps blocking

Hi all, after 3 days I'm still trying to get my reprap to print. I'm running a j head 0.4mm nozzle with pla at 185. For some reason, whenever I manually extrude it comes out as a loop and it constantly keeps blocking if I turn the printer off and then go back to it. Please can someone help?
Thanks
Ben

All I can say is I'm running at 230 and 60 for pla, 240 and 100 for abs. Until I installed a fan above the extruder blowing on the filament were it enters i was melting the filament above the hot zone causing endless failures. Since installing the fan I'm getting awesome prints on my $400.00 Prusa i3 knockoff. Also, if you heat the hotend to 80c (for pla) and pull out the ftlament, it will take everything out right to the nozzle hole. Run a wire through the hole to check for clear, cut your filament end nice and square and reinsert. I used a 40x40x20 mm fan with a 100 ohm pot for adjustment. Hope this helps.

Elwood127, Can you please post a pic of your fan you added? I have the Aurora Z605 and it came with one fan and mount, but it is focused on the end, not the chamber. This was working great with the sample filament that came with my printer. But I have just started with a roll of ABS and am having a hell of a time with the extruding. I am thinking part of it is temp control, because I think it keeps lowering my temp when it starts. But I keep getting a bump from the extruder motor because of back pressure and the line it is laying down gets thin at that spot.

I've just got a 25mm fan that's aimed at the all metal j head fins now and along with blue tape on the bed with temps at 185 and 60, my pla is printing great.
Thanks for the help.
Ben

Hey Willy, I have no bumping at all now. Fan is everything. Also, today I jumped in feet first into speed settings in Slic3r. For ABS I'm at 240 and 100c with these speed settings.
Perimeters-70mm
Small Perimeters-30mm
External Perimeters-70%
Infill-100mm
Solid Infill-90mm
Top Solid Fill-80mm
Those are the only ones I've changed so far. Had to back off slightly after initial bump up to 100mm, extruder started bumping trying to keep up. I reloaded a part that I ran last night at old settings that took 51/2 hrs. With new settings Slic3r said 3 hrs. Perimeters aren't quite as smooth so I'll probably back those settings up a little more. Part quality seems better than at slower settings, go figure. I've attached 2 photos of fan mount and 100 Ohm pot for fan control speed. I back the pot off of full on just slightly to not stress the fan. I ran wires directly to spare 12 volt connectors on power supply. Only draw back is limited access to hob and filament if there is a bunch up. I also uploaded my drawing file for the fan mount. I made it with PLA but it broke soon after. Reprinted it with ABS and all is good. One more thing, I started using Purple Elmer's Glue Stick instead of ABS juice on my build glass, it's fantastic. Rub it on, dries clear in seconds and sticks like a mother. Let glass cool and part literally pops off. Great stuff. Hope all this helps. I know my learning curve was brutal. Thanks to all of the members here. Would have been lost without you. If you need any other setting suggestions I'd be happy to help. Brian.

Quote
elwood127
All I can say is I'm running at 230 and 60 for pla, 240 and 100 for abs. Until I installed a fan above the extruder blowing on the filament were it enters i was melting the filament above the hot zone causing endless failures. Since installing the fan I'm getting awesome prints on my $400.00 Prusa i3 knockoff. Also, if you heat the hotend to 80c (for pla) and pull out the ftlament, it will take everything out right to the nozzle hole. Run a wire through the hole to check for clear, cut your filament end nice and square and reinsert. I used a 40x40x20 mm fan with a 100 ohm pot for adjustment. Hope this helps.

what temperatures are you melting PLA at? I keep running into the same issue. currently im at 200 nozzle and 65 bed and its not working.