Please help with strange one-sided under extrusion on ABS prints

[FeherAron 0]

Hello everyone!

I've purchased an Anet A8 3D printer, and after finishing the initial PLA sample, I've ordered some ABS filament from farnell. 

Somehow I've managed to tune the settings so everything went relatively good for approximately a month.

Last week I've updated Cura to version 3.6.0 and from that day on everything became worse. If I print my calibration cube (img1) everything is nice, but any other print has under extrusion on one side (img2, img3). The setup I use (I think it's the same before the update of the software):

 

Layer height: 0.08 mm

Infill: 20% density, grid pattern

Material:  240°C Printing temperature, 85°C Plate temperature, 2mm retraction distance 25mm/s retraction speed

Print speed: 50 mm/s

Cooling: 75%

Support: Everywhere

Build Plate Adhesion: Brim, 8mm width, 20 line counts

 

So far I've been talking to some colleagues, who only use PLA, and they said that the retraction could be the culprit. I've tried with retraction enabled, disabled, but no effect.

img1 - shows the reference cube.

img2 - shows the parts with one under extruded side.

img3 - shows some more parts with the printing cancelled, so we can see the inside of an object.

 

I'm starting to get a little frustrated, since this build will be used for  the development of lab exercises in the university...if only I could print them normally, so any help and advice for improving this mess would be appreciated.

 

Thanks in advance,

Fehér Áron.

 

PS: I'm relatively new to 3D printing, so please be gentle.

[Smithy 1,144]

Hi

it looks like under extrusion, but why only on one side? So I guess it is not under extrusion, but maybe your cooling fan is blowing too much cool air on this side and you get some kind of warping of the layer itself before it can get bonded to the previous layer.

 

Check if you fan, I think the A8 has only one, is on that side. If so try to decrease fan, 75% is normally too much for ABS, turn it off completely or try around 10% fan speed.

 

That said, printing ABS without an enclosure is very difficult to not possible. You need an enclosure around your printer to keep the warm air inside.

[FeherAron 0]

Thank you for the fast reply.

My fan duct is placed in the front, so the air should go to the front of the objects. But even if the fan would be the problem (I don't think it is, but tomorrow I will give it a try at 10% speed),  why didn't I have any problem so far (I've attached an image of the incomplete seesaw model)?

[Smithy 1,144]

To be honest, I don't know and I was just guessing it could be the fan. It looks as under extrusion, but I have no idea why it is only on one side. 

 

You could also try to rotate the object by 90° to see what happens.

[yellowshark 153]

OK firstly, you say it worked before upgrade but not now. I assume you are printing the same model with same settings (as far as you know) and the same filament, otherwise the statement is not really valid. Assuming yes, have you compared the 3.6.0 and the prior version settings in detail - I mean every single setting whether you use /change them or not- to see if something has changed that you were not aware of.

 

It looks like a very small piece - do you have your minimum layer time set to a minimum of 10 seconds?

 

What width of filament are you using - is that what is defined in your Cura settings?

 

What is your setting for flow %?

 

Is it right that all the model parts in your 4th picture were printed before you upgraded to 3.6.0?

 

What is your z-alignment setting? If it is not random is the new layer starting in the area where the possible under-extrusion is happening?

[FeherAron 0]

@Smithy I'll create a 90° print sideways, and one oriented with the shorter side down, and post my results.

@yellowshark The model is the same. The settings are the same, with exception to the retraction - this is what I was testing without results. I am generating a RepRap style Gcode, and the setting part is the same.

Minimum layer time is 5s.

I use a filament with 1.75 mm diameter, and I've measured it on a 10m piece with a micrometer and it holds between 1.748 mm and 1.753 mm.

If you mean the flow rate compensation, that's the default 100%.

Every part was printed before the update.

Z seam alignment is set at the sharpest corner - Now this is a setting I can't remember if it was before 3.6.0 or not.

 

Edited December 18, 2018 by FeherAron

[yellowshark 153]

This is all very strange! I would definitely set minimum layer time to 10 secs. OK so on layer change it starts on one of the rear corners; is it the right hand side I.e. the side with the mess? I am just wondering if it travels direct to the mess area and the previous filament has not had time to cool before you come along and print more filament, so we are not looking at under-extrusion but just a simple mess; clutching at straws here!

 

Are you able to print PLA too. It might be interesting/helpful to see a PLA version. 

[FeherAron 0]

@yellowshark I'll set it to 10, and test it. The starting point is right in the middle of the problematic side. I've ran out of PLA at home, but tomorrow I'll ask my colleague to print my design with the university printer, which uses PLA. 

 

I've created a test design with cylindrical and box holes and extrusions. This print clearly shows that my problem is somewhere with the round shapes.

Edited December 18, 2018 by FeherAron
Print update

[yellowshark 153]

Ah, well I am not sure where you are now with the retraction setting but it was 2mm which seems awfully short to me. But I am talking about 2.85 PLA and I do not know if that needs different settings. It may just be that you are not retracting enough so when the printing starts on the next layer you are over-extruding. Probably worth trying say 5.5 unless you know it needs to be shorter for 1.75/ABS. I am not sure but I have never seen your symptoms before. It could be cooling but I do not understand why the problem is localised if it is.