Blobbing... technical term!

Hi,

Can anybody help me identify potential sources of this problem please? The attached is whilst printing a raft.

I recently updated firmware to 1.07k think it was from 0.78. I use pronterface.

Haven't used printer for a while so not sure if related to firmware or not.

Thanks,
John

The picture is a bit too low res. to tell anything




Erik

Bigger version attached.

Thanks

I only printed with raft once, but remember it was laying down plastic nice and thick, do you hear a knocking sound from the extruder? - or tried to lower the printing speed? - the repeating pattern seems a bit strange though..



Erik

Hi Erik,

The raft just shows a good example of what is happening. It's the same with all prints just easier to visualise with this raft.

Didn't notice anything strange noise wise. The pattern is so uniform it's what makes me think it's not just the nozzle too close to the bed. Have tried some increased z heights but same up to pint where it's just laying on top of bed (not sticking).

John

It looks like your z0 height is too low - there are a few step by steps on this forum on how to check that, so I won't repeat the whole exercise here, suffice it to say that at z0 the nozzle should very lightly grip a standard piece of paper. There might be an over extrusion problem too.

Basically what happens is that the plastic can't extrude because it's pushed against the plate, so the pressure builds up until it's enough to lift/tilt the head up, and the plastic comes out in the blobbing line. That drops the pressure again and the head drops which blocks the nozzle, so the pattern repeats.
The second line happens in the same place because the nozzle is being lifted by the bumps of the previous line of plastic..

Edited 1 time(s). Last edit at 06/27/2016 03:23AM by VortyZA.

Thanks Vorty.

Sounds like this is the problem. Something has happened to my bed in that it's got a low point half way along one edge strangely, so this is probably a by-product of me trying to compensate for that.... I'll take the bed apart and start there. Cheers,
John

Edited 1 time(s). Last edit at 06/27/2016 08:36AM by johnrees.