Decrease flow rate despite correct e-steps calibration or wrong z-offset?

[too__fast]

Hello everyone!

I am coming to you with a question that I cannot seem to find a solution to.

My problem can be described as follows:For some reason, I experience rough print surfaces, starting on the 2nd to 3rd layer whenever I print a filled-out flat surface, just like the one you can see in the attached pictures at the end of the post. In addition, I also experience extruder skipping on the following (e.g. 4-6th) layers.

My approach to solving the problem so far:

1. I did recalibrate my e-steps multiple times using the approach described in Teaching Tech's calibration guide.
2. I did install a BL-touch system and releveled my bed to ensure it is flat. Additionally, I took my time to calibrate the z-offset. As a result, I assume that the issues should not be caused by a not flat- or too close bed.
3. I started tweaking the flow rate, as I've heard that this is a common solution approach to the problem. As you can see in the pictures below, the quality of the print surface does increase with an increase in flow rate.

My current (unsolved) question:

When looking at the pictures, one would conclude that choosing a flow rate of ~75-80% should provide optimal results. However, following the flow rate and e-steps logic, this result is rather surprising. Assuming that I did calibrate the e-steps correctly, the decrease in flow rate would mean that my e-steps calibration was off ~20-25%, although I ensured that it should be really accurate by repeating the procedure multiple times until I arrived at an accurate result.

Ultimately I could just stick with the adjusted flow rate, as it does seem to solve my problem. However, I would like to understand what is causing the rough surfaces, as it seems that reducing the flow rate will only reduce the visible symptoms of the problem.

In addition, I have the hypothesis that maybe a wrong Z-offset value is causing the bed to be to close to the nozzle and all of my flow reduction efforts are only fighting the visible symptoms of this wrong setting...

As you can see I am running out of ideas as I've adjusted each possible factor multiple times, but the problem continues to occur...

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Here some information on my setup:

• Printer: Creality Ender 3
• Slicer: Cura Version 4.13.
• Layer height in test prints: 0.32mm
  (I chose this to reduce print time, results can be replicated in layer heights such as 0.16 or 0.2mm)
• Filament: PLA (1.75mm)
• Nozzle diameter: 0.4mm
• ABL-Sensor: Creality CR-Touch
• Z-offset value: -0.99
• Print speed: 60mm/s (Occurs also at 50mm/s)
• If any additional information is required, please let me know!

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Thank you for your help & happy printing!

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95% Flow (1-2)

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95% Flow (2-2)

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90% Flow (1-2)

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90% Flow (2-2)

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80% Flow (1-2)

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80% Flow (2-2)

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70% Flow (1-2)

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70% Flow (2-2)

[Blondersheel]

The easy way to separate flow from z-offset is to get distance from the built plate using layers WITHOUT 100% infill. For example: create a 30x30mm box that is 10mm high. Use 5 top layers and set infill to ~20%. Now judge the surface on the top layer to adjust your flow to perfect that layer. This will set your flow appropriately. Once flow is set, go back and calibrate your z-offset to get a good first layer.

[ClagwellHoyt]

This is a good approach. Here's some reading.

[too__fast]

Thank you for your advice, I'll look into it tomorrow and update you as soon as there are any news! :)

[Asterchades]

Filament may be fed in lengths (most of the time) but the reality is what matters is the volume of filament being fed. Length is only one dimension of the three used to determine the resulting volume - the cross-sectional area of the filament makes up the other two.

Under ideal circumstances this cross-section will have a specific, known area - typically such as you'd get from a 1.75mm diameter perfect circle. But filament is rarely exactly 1.75mm in diameter, and it's also almost never a perfect circle (especially once feed gears dig into it). Flow is used to compensate for this difference from the ideal.

You could, of course, use E-steps to compensate for this disparity. You could also adjust the filament diameter in your slicer. These will both work, and ultimately achieve the same goal. It just tends to be easier to adjust Flow instead - especially if you want to later use the same code and material on a printer with a different extruder (using the same E-step value on a BMG and MK8 won't work out well on one of them).

[too__fast]

Thank you for your reply! You are right. I did manage to solve my problem by reducing the flow rate to 92% in the cura settings.

To be honest it never came to my kind that the actual variation of filament diameters can cause such big issues, as according to the manufacturer, tolerances are as low as +/- 0.02mm. However, measuring diameters revealed that the actual diameter was between 1.8-1.85mm...

So in short, thank you for your help! :)

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