Periodic layer delamination

So I have been printing just fine for a while, but to resolve some rapping and delimitation I got a heat lamp. I ended up putting to close to the abs extruder parts and got everything distorted.
So I installed my spare gregs extruder printed parts and started printing calibration objects. While printing a 1 layer wide part I got a layer every 4cm getting not extruded completely. So I checked the print and realised the bad layer happens every revolution of the big gear at the same spot after retracting.
I tried changing the big gear, did not change anything.
I tried lowering retraction.
I also checked the hobbed bolt, it seems ok.
I dont think it is linked but I canged from a Jhead to a E3dv6 when changing the extruder parts, and I am printing Abs.

Do you have any other idea on where the problem could come from ?
Thanks

Edited 1 time(s). Last edit at 12/14/2014 12:38PM by akkotaire.

If it's occuring every rotation of your extruder gear then that sounds like an extruder issue. Try heating up your V6, then turn off the extruder motor and extrude by hand-turning the big gear. You should be able to feel if there is a high friction/torque spot in the extruder. Since you have changed everything else I would still suspect the hobbed bolt. Is the extruder skipping stepps on the failed layers? Perhaps you are running at near the limit of your extruder motor's torque and there are one or two teeth on the hobbed bolt that are a bit less sharp, causing the extruder to have to work just a bit harder there. I've noticed that there is a significant increase in torque required to extrude over the filled teeth of a hobbed bolt that has some plastic in the grooves. I assume it would be similar if there were a dull tooth. In either case the plastic filament "climbs" higher on the bolt which causes an increase in extrusion torque required at that point.

Also if this is a bowden extruder you might look for friction in the bowden line.

And just in case you might try checking for a bit of grit in the nozzle. They can be intermittent as the grit gets pulled out of the nozzle opening on retraction then slowly works its way back in. A warm pull with PLA is a good way to completely clear the nozzle. Or just clean it using your method of choice and check the nozzle visually.

Thanks a lot for the clear information and suggestion. I checked the hobbed bolt again,
I took everything apart and with only the hobbed bolt and the bearings I could feel a pressure at some point when turning, I think it is slightly curved. I cant see it, but it must be that.
Thanks again