Hi Folks,
I'm using a J head MK V clone on my mini Kossel that looks great in terms of machining, dimensions and sticking to the proper design (right number of fins on the PEEK etc). It was supplied with two PTFE liners, one for 3mm filament and one for 1.75mm. I'm using 1.75mm PLA to print with and am getting a lot of blobbing and drooling.
There even seem to be times when filament is actually pulled out of the head during a move and one part of a model develops a sort of beard (for instance on the inner edge of the rear fins of "mr jaws" the shark from thingiverse).

It also takes a while to start extruding at the beginning of a print (even though it's drooling nicely while heating up) so the first 10cm of a skirt will be unprinted.

I thought this might be a problem with the melt chamber being too big for the filament and queried the vendor but he claims no complaints from many customers... what does the reprap hive mind say?

Cheers,
Robin.

While the nozzle is idle, the filament will ooze out through gravity. This means that if there is a period of time - say 60 secs before the print begins, then the extruder has to "catch up" so to speak, to replace the lost filament that oozed. What i do,(and I control temps manually) is, after temps of bed and hotend are up to target, is to extrude 10-15mm of filament manually to get a "head" then immediately press the "Print" button. It will start printing the skirt fully then from the beginning. Set your temp to 185C initially to see how it goes.

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Waitaki 3D Printer

+1

Blobbing and drooling sounds like too high temperature. It's normal for filament to ooze out slowly under gravity, but it should come out as a nice clean strand, not a blobby one.

I have set up my slicer such that it adds some starting g-code so that upon pressing print it hovers the head 1mm above the bed in the corner of the print area, extrudes 5mm of filament, zeros the extruded amount and then starts the print.

If you have extrusion set to absolute then you must zero the extrusion before printing (or else the extruder is liable to spin backwards undoing any prime)