Ideas on what is wrong?

[Larry Bowers]

Hi,

Been printing with my new Ender 3 Pro for a few weeks now and all of a sudden the nice clean top layers are not so clean anymore. I tried making one before this and it was a lot worse so I changed to Creality white PLA (was using black). I thought perhaps over extruding so I double checked the E-Steps and it was slightly over extruding so I adjusted it an tried again changing to Creality white and got this. This one is better than the first one I made but not like other items I've printed in the past couple days. I don't believe I changed anything profile setting in the last few days. I was running a Dr Vax bed leveling STL today and ran it three times to make minor screw adjustments to the bed. I saw this pattern starting to show up while running it the Dr Vax STL, but not to this degree. Would this be referred to as 'scaring' or something else?



Using Cura 4.10.0 slicer. .4 nozzle. .2 layer height. Print speed 50mm. Creality PLA (200c extruder / 60c bed). Retraction enabled - 6MM (I think that is Cura default). Combing Mode - Not in Skin (default distance with no retraction is 30mm - Cura default).

So what happened and ideas on what to try to fix??

Larry

[Ender5r]

This looks like the nozzle is too close to the printbed. Have a look at this: https://www.youtube.com/watch?v=RZRY6kunAvs

[Larry Bowers]

Ender5r,

I would agree with your thought the bed is not level, but this image is after 10 layers, 2mm, has been printed.

I downloaded the file in the video and will test it again.

Thanks

[Ender5r]

The 2 things (bed level & nozzle offset) aren't necessarily related. The bed could perfectly "level", in that all points of the bed are the same distance below the nozzle, but the Z Offset could be such that the nozzle is too close to the bed when printing.

[Geit]

What did you use as infill? It looks like the entire plate has a very low infill and the top layers are sagging in. The diagonal dark lines seem to be the infill pattern and one can clearly see the surface to fall in at the sides of those lines. The fact that you are printing very slow (60mm/s is kind of default) is effecting this, too and not helping.

You probably need more infill or at least one additional outer wall at the top to compensate the sagging.

To me it looks like your entire surface is just a gigantic bridge between infill, which is fine, but you need more top layers to get a proper finish. For a thin part it mainly does not matter how high you set the infill. The material usage is small anyway. I would go for at least 40% infill on a thin part and use two top layers. Or less than 20% and three top layers.

[Ender5r]

Interesting observation Geit. I look forward to hearing more details.

[Larry Bowers]

I'll first admit I am new to this and Cura slicer settings so I'm probably not understanding them correctly. This model is 1mm tall with a .2 layer height so a total of 10 layers which shows in the slicer preview. The infill is 15%, but the layers show 5 bottom layers and 5 top layers so to me there would be no infill.





To me it appears when the nozzle starts its diagonal move it extrudes a little more than needed and 'plows' through the excess and by the time it reaches the end of the line its extruding an amount that does not squish out the sides. For instance the upper left and lower right side of the holes appears like the nozzle is pushing material to the sides. Sorry for my choice of adjectives.

Here are the speeds I'm using. I think these are the defaults...



I'll mess with this some more. I will test a model without holes at the same thickness and make it thicker to see when infill is used if the top surface looks any different

Thank you for your advise

Larry

[Ender5r]

From your description of "plowing" it really does sound like your nozzle is too close. Try printing the test squares I linked to and, while the print is ongoing, go into the menu system on the Ender 3 & change the Z Offset, setting it to move the nozzle up a little (say, in 0.1 mm increments) as it prints the diagonal infill lines.

[Larry Bowers]

OK ran the test squares. Followed Hobby Hoarder's instructions and preheated the extruder and bed 200/60c and used preliminary paper gauge.

I restarted the test a couple time because nozzle initially not low enough. Overall I'm pleased with the results. I have uploaded picts with light from two different angles for each test square. Te front right I think is a little to low right now.



Front Left (top light)


Center (top light)


Back right (top light )


Back left (top light)

As the she skirt was being laid down I was live adjusting the leveling screw and I must have put upward pressure on the screw causing the nozzle to get to close to the bed


Front right (top light)

I'm thinking nozzle is to close

I did not make any Z adjustments while printing

Larry

[Ender5r]

Back left looks the best. The center is pretty good. All the others still look a bit close -- only a tiny bit, but the "bumps" on the surface are the telltales. The surface should feel smooth & pretty even. Overall, well done. You are really close at this point.

[Larry Bowers]

A question Ender5r on the Z Offset you mentioned. If I home the nozzle, disable the steppers and move the nozzle to above one of the leveling screws and us a piece of paper then run the square test and make a Z Offset when I home the nozzle again will it be adjusted by that Z offset?

Also this 'plowing' is happening multiple layers up the model so if I change the Z offset for layer 1 and the layer height is .2 the Z Offset would have only been done to the bottom layer. Maybe I'm over thinking this.

[Ender5r]

Really good question. After making any changes such as Z Offset, be sure to use the "Store Settings" menu option to lock them in the firmware on the control board. Sorry I didn't mention it before.

And remember, as virtually everyone on Youtube (including Hobby Hoarder & DrVAX) say, be sure to preheat the nozzle & printbed before levelling. In fact, I level mine with them at the temps I will use at print time (i.e. I don't arbatrarily set the printbed to 60C when I print with it at 80C). All metal expands & contracts with heating and cooling, so the offset will change depending on temperature.

[Larry Bowers]

huh, I might have found a clue....

Geit asked about infill percentage. My response was I don't feel there was any since the model is only 2mm thick and slicer settings of 5 bottom and 5 top layers. At .2mm per layer there is no infill.

So I increased the height to 5mm and that gave 3mm of infill. The slicer was set to 20% infill.

So during the print infill was printed...


When finished I was pleased with the results


The surface is not nearly as rough as the 2mm thick model which almost seems there was over extrusion in places. I'm OK with this result.

So maybe it was my own issue....

[Ender5r]

I think the extra height helped, partly by allowing for any levelling issues to be ironed out by filament settling, which is fine. There's only a small amount of "ghosting" on 1 side of each hole. Your photos are good; they show off the issues quite clearly.

However, I would still make the small adjustments to get the 20mm squares even better than they are. If you haven't already seen it, watch this DrVAX video, & take note of the 1st layer torture test he shows in the video. There's a link to download the model from thingiverse below the video window. First layers are critical to successful prints, so a little extra time spent on getting them right is usually worth it.

[Alanaland]

I have had a similar problem, uneven surface. Found the X gantry needed adjusting. With the Z stepper on one side, i.e. not duel Z steppers, the other end of the horizontal X carriage can allow the nozzle to track poorly. To test this print a 1mm high 30X30mm square on the left and right side. The left hand square ( near the Z stepper ) will have a smoother surface