blistering suddenly appearing

Hi All,

I guess I should address this to a dedicated 3D print forum but everyone is so knowledgable and helpful her, I thought I would try it first...

My 3D kossel has worked perfectly for ages, no issues at all until the last couple of days. Today I put out a print that had a flat bottom directly onto the print plate and a series of blisters appeared as per the photos. It appeared that the print was going down but not firmly attaching on the unsupported side and then lifting up and away as the head moved past. The end result was a series of ploughed furrows that instantly killed the print when the next layer started because the ripples interfered with the print head.

I tried several changes including bed temperature settings, nozzle temperature, print density, etc. Finally, needing the job done, I printed on a bed and the result was successful.

I put it down to a probable height control issue.

The next print has a flat surface some 12mm above the bed and exactly the same problem appeared...

Any thoughts?

The filament has not been changed, in fact nothing has changed over the last few weeks so I am rather bemused.

Hoping someone will take a look and recognise the problem.

BR
Simon

It looks a bit like 'pillowing' caused by too-thin a top layer or insufficient cooling fan, but doesn't look quite right.

Things to think about: First has your filament been exposed to humidity? Second, it could be a worn print nozzle. Is your printer running too cool? Any of these could cause poor adhesion.

The worn print nozzle, rather than letting too much filament out, causes symptoms of under-extrusion - you get short fat beads rather than long thin ones, so they periodically run out.

Edited By Neil Wyatt on 25/09/2017 21:15:09

Has it lifted from the bed? This could be ploughing???

Neil,

I don't think its that - it has been working well up until now, and nominally nothing has changed.

Humidity was a good call, we have had a couple of much more humid days here than normal - but when I changed to a virtually sealed different filament, the result was the same.

Cooling - again, if it was just layer #1 then I would think it likely but this was 2 hours into a print and its some 20mm above the base. And it only seems to happen when travelling in one direction (more difficult to confirm though).

No obvious reasons why the nozzle would be suddenly worn - but I tried a cleaning cycle that may be of use to others:

Nozzle removed and dropped into my old ultrasonic tank along which was loaded with a solution of caustic soda (all taking place out in the open air I hasten to add). A 5 minute run removed all traces of PLA from the externals and the thread. I then cleaned and dried the nozzle in clean water and turned the blowlamp on it for a few seconds which resulted in a blob of molten filament popping out the large end. Back into the ultrasonic then resulted in a visably very clean nozzle.

Had no effect on the problem however.

@Robin - it seems to happen at all levels - the photos I didn't upload show the same effects on layer #1.

I am starting to think its some alignment issue that has just happened, but nothing is obviously wrong.

Thanks for your thoughts though.

Simon

Edited By Simon0362 on 26/09/2017 13:32:28

Nozzle wear is odd, it caught me out because I wasn't expecting it and the problems came on very suddenly.

The people who supplied my printer kit suggest a nozzle change every 2 rolls of filament, so worth offering it up to a calliper to see if you can estimate the size. Mine was closer to 0.6mm than the original 0.4!

What printer do you have?

Neil

Looking at the photos, it is definitely caused by poor adhesion between layers. The fill and thin walls are OK, but the top surface is a continuous sheet so shrinkage is pulling the top layer away and towards the previously printed parts.

So... measure your filament, is it undersize?

Check your nozzle, is it oversize?

Check your print temperature too.

Neil