1
$\begingroup$

I have a LultzBot TAZ 6 3D printer and the software I use for my prints is "Cura LulzBot Edition - 3.6.3". Recently, I have begun to play around with the parameters in Cura relating to initial layer adhesion. One such parameter is the Initial Layer Flow Rate.

Now, after manipulating this parameter several times and evaluating the pieces that have been printed subsequently, it seems quite apparent to me that a manipulation in this parameter is affecting all subsequent layers that are printed.

For example, if I increase the Initial Layer Flow Rate from the default setting of 100 % to 130 %, layer 2, layer 3,...layer n all appear to be printed at at a flow rate of 130 % resulting in prints that are clearly "overextruded" (e.g. the finished surfaces are incredibly uneven, bumpy, etc).

Similarly, if I decrease the Initial Layer Flow Rate from the default setting 100 % to 70 %...all subsequent layers are clearly underextruded (e.g. walls are not connected at all and floor/ceiling have visible gaps).

Why is this happening? Directly above the Initial Layer Flow Rate parameter is a parent setting that is simply named "Flow". (refer to below picture)

Cura Parameters

Do I need to manipulate flow in order to avoid this from happening?

All I want to do is change exclusively the initial layer's flow rate (for better adhesion on larger pieces)...but my current method is not accomplishing this. Any suggestions?

$\color{red}{\text{EDIT}}$ - After reading the comments, I just wanted to clarify that I have let my parts "be printed to completion". The obersvations that I am making about underextrusion or overextrusion are in reference to the total structure (not just the first several layers). These are large structures (~12 hour prints).

Improve this question
$\endgroup$
4
  • 1
    $\begingroup$ Hi S.Cramer, welcome to the site. You could include photos for better replies. Flow in 3d printers is how much plastic you extrude, so this sounds correct. There can be a residule effect (more melted plastic in the barrel) between the layers. Its not much plastic to be an over vs under. I'd let it keep printing and see what it looks like after 5 or so layers. $\endgroup$ – StarWind0♦ Mar 10 '20 at 21:34
  • $\begingroup$ @StarWind0 I think you may have misunderstood my post. I HAVE let it finished printing complete structures...using several different values for the initial layer flow rate. In all cases, it is evident that the initial layer flow rate has completely influenced the overall structure of the print. Hence the question. $\endgroup$ – S.Cramer Mar 10 '20 at 21:55
  • 1
    $\begingroup$ Welcome to the 3DPrinting Stack! $\endgroup$ – 0scar♦ Mar 10 '20 at 21:55
  • 1
    $\begingroup$ In the generated G-Code, flow-rate translates to G1 Xn Yn En.nnn (extrude n mm) commands. Cura marks each layer in the G-Code with "Layer: n". You could have a look, if the extrusion length differs for the same line in layer 1 and 2-n $\endgroup$ – Michel Feldheim Mar 11 '20 at 16:36
2
$\begingroup$

If you're over- or under-extruding by a 30% margin, there is going to be so much excess or deficiency of material in the first layer that it will take a few layers to "catch up". Normally you would only adjust the flow by 5% or at most 10% unless you're using it to correct for compression of the filament in the extruder gear (for flexible filaments), but adjusting first layer flow only is always a hack to work around incorrect bed height or adhesion problems. You'd do much better to figure out the right solution to whatever problem you're trying to solve with flow.

Improve this answer
$\endgroup$
5
  • 2
    $\begingroup$ Exactly my thoughts! If you need that much flow, you may better check your nozzle to bed distance at Z=0. After printing kilometers of filament on glass, I have never touched flow adjusting settings. Only my first Slic3r prints many years ago on an Anet A8 used first layer increased flow because it was said to help it better adhere, but actually it is not always needed, probably only when the bed surface is very course $\endgroup$ – 0scar♦ Mar 11 '20 at 5:47
  • $\begingroup$ Thank you for the response. However, I want to hone it on your phrasing: "[...] will take a few layers to 'catch up'. " As I stated in the edit of my post, these are very large prints. I print at a 0.25 mm/layer and the total height of my prints are 50 mm +. That means that the presence of excess or deficit in the first layer is propagating over 200 layers! When you say "[...] few layers [...]" surely you do not mean 200. This is why I believe it is an issue with the parameter and EVERY LAYER is, in fact, being printed at this flow rate.. $\endgroup$ – S.Cramer Mar 11 '20 at 16:41
  • 1
    $\begingroup$ @S.Cramer: You could read the gcode file to test that hypothesis. $\endgroup$ – R.. GitHub STOP HELPING ICE Mar 11 '20 at 18:37
  • $\begingroup$ @S.Cramer: Did you determine one way or the other whether Cura was doing something wrong here? $\endgroup$ – R.. GitHub STOP HELPING ICE Mar 14 '20 at 23:00
  • 1
    $\begingroup$ I am not particularly familiar with "gcode", so I was going to read up on it once I had time (in order to carry out your recommended approach). I will update the post with an edit after I investigate. Cheers~ $\endgroup$ – S.Cramer Mar 15 '20 at 1:27

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.