Sudden change in quality on outer walls of print.  

RE: Sudden change in quality on outer walls of print.

Lubricate the rods, check belt tension, check that the grub screws on the motor axles didn't come loose.

RE: Sudden change in quality on outer walls of print.

All good.. I didn't think it could be the X or Y, otherwise you would only see the issue in one direction.. Unless both axis were affected.

I have printed it on the MK3 and its perfect.. But then I looked closer at the Mini version and it looks like under-extrusion.. The bottom layer doesnt' look right.

I am thinking that the extrusion width is fluctuating.. This looks like a blocked nozzle perhaps, but I did a cold pull and its absolutely clean.

RE: Sudden change in quality on outer walls of print.

Nozzle itself worn out?

RE: Sudden change in quality on outer walls of print.

That is very possible.. I am still on the original.. I am just doing a flat 0.2mm test to see what the extrusion looks like over a bigger area.. and will then check the nozzle..

RE: Sudden change in quality on outer walls of print.

Very much an extrusion problem.. I just did a 30 x 30 0.2 print (one layer) and the entire thing is just a layer of unjoined lines.

Its odd. If I extrude into thin air, the filament comes out perfectly well.. But I am going to look at the nozzle next.

RE: Sudden change in quality on outer walls of print.

Changed the nozzle and its exactly the same.

My first layer looks like this.. It almost looks like the first layer height is wrong.. But it looks to me more like an extrusion issue...

RE: Sudden change in quality on outer walls of print.

Come to think about it.. I am not sure I have done much printing since I did the 4.4.1 upgrade a few weeks ago.. Could this have been a side effect of that? Its almost like the E steps are wrong.. And I can't for the life of me remember how to check/set it.

RE: Sudden change in quality on outer walls of print.

I started to wonder if it was first layer height.. So I started to wind it down and the first layer is joining up and getting better.

This makes no sense.. My layer height has been set to 0.9mm since day one and never had a problem.. I am now at 1.0mm and still havn't got it dialed in.. How could it have changed? By so much?

Now I have the first layer almost right, I am now printing a '3D' object to take some measurements so will let you know...

RE: Sudden change in quality on outer walls of print.

Could be a loose PINDA holder. Also, if you changed the nozzle, you need to redo the Live Z as the new nozzle will never screw in exactly as the old one did. I have this calibration strip https://www.prusaprinters.org/prints/105404 that lets you check 8 settings in in one 6 minute print. 

RE: Sudden change in quality on outer walls of print.

Cheers for that.. I fully expected to have to change the Z height after a nozzle change.. But the issue I had was before.. Suddenly, almost overnight without reason this happened.. And if its the first layer height, it will always be a mystery.

I guess its possible that the tip of the nozzle had worn down to a point where the first layer wasn't "joined" and the new nozzle is shorter than the original.

It all a possibility.. Either way the first layer is better now, so I just have to see whether that fixes my issue with surface walls being uneven.

RE: Sudden change in quality on outer walls of print.

Well.. I see it.. But I don't believe it.. The print is perfect now... Better than the MK3 infact. The walls of that object are straight as an arrow now.

It was a first layer thing after all.. I can't see how or why it changed, but really happy its working again.. Cheers.

RE: Sudden change in quality on outer walls of print.

Glad it worked out. Don't forget—3D printing is more similar to voodoo than science.

RE: Sudden change in quality on outer walls of print.

Something still isnt' right.. Here are 4 test prints:

The rightmost one is since I got the layer hight right.

The next one in from the right is the original (And slightly worse than the right).

The black on is from the Mini, after I changed the layer height and its pretty much perfect.

And the one of the left is the same green filament as the others on but on the MK3.. And it also looks pretty perfect.

So it looks like the Mini is struggling with that green filement.. But this is where it gets odd as I noticed the problem first yesterday on the the BLACK (but a different print).

I now need to do some more test prints to find out whats wrong..

RE:

I am 100% sure I have a problem.. I have some objects that I print regularly and have made 100s of them.. They are beautiful.. So smooth and its almost impossible to tell they are 3D printed.

But I just printed one now, from the same STL file.. And its horrible... I have the same effect as shown in the photos.. And interestingly, the bands appear to repeat a constant pattern..

Here is what it looked like before:

Here is the print now:

And an extreme closeup of the "pattern":

If it were random, I would think it was mechanical.. But that repeating pattern is odd, don't you think?

RE: Sudden change in quality on outer walls of print.

Have you try to replace the PTFE tube inside the heatbreak? You said earlier that you've been using mini 1000 hours, with that hours of usage the PTFE could worn out. The PTFE tube length should be 43.4mm

RE: Sudden change in quality on outer walls of print.

Yes definitely check ptfe

RE: Sudden change in quality on outer walls of print.

Thanks all for your help.. It never occured to me to check the PTFE tube and since its been a long time (years) since i last changed, it I was hopeful it was the cause.

So I took out the connected and pulled out the tube (it was quite well stuck in) and I expected to see it distorted/melted in some way.... But it was perfect.. And was EXACTLY the right length, so I was a bit disheartened to find this.

But. I was looking down inside the hotend and something was blocking the way.. And when I fished it out, it was a flat, ultrathin piece (perhasp 10x5mm) piece of clear plastic.. Like some kind of wrapping, or even a slither of PTFE.. It certainly wasn't filament and I guess because it was flat, it pushed out got out of the way when filament came through

I don't know how it got there, but I am wondering if it was wrapped around some filament and got 'sucked' in? Perhaps unlikely, but it was there.

I have now reassembed and done a test print and its back to being perfect again.

I am not 100% sure its fixed so will have to do more tests, but its looking good..

Thanks all.

Jon

RE:

For me this looks like there is someting in the extruder. When you have some dirt on the extruder gear which touching the filament, the diameter changes particularely. This would explain the pattern where you have inconsistent extrusion.