E steps/mm correct, but inaccurate wall widths?

Hello, all. Trying to understand something here. I was under the impression that, when your E steps/mm value is spot-on, and your line width is set to 0.5 mm, when you print a thin-walled object, such as the one is this set: , it SHOULD print, with 0.5 mm width walls. However, I'm not getting that. I'm getting, what looks like under-extrusion and, when I measure the walls, I'm getting 0.35 mm wall widths. This is with a 0.4 mm nozzle and a manually-set line width of 0.5 mm. Am I missing something?

Thanks, in advance, for the feedback.

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Prusa i3v 8", Hexagon Hotend, Itty Bitty Belted Extruder

How do you decide that your steps/mm is "spot-on" if it isn't giving you the right line width?

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

I marked the solid filament, set the printer to extrude 100mm, remeasured, and it was 100mm. So, supposedly, spot-on, from that test, so clearly, something else is off.

Edited 1 time(s). Last edit at 02/28/2020 04:54PM by KCheshire.

When you are printing, are you concerned about the filament going into the extruder or the plastic coming out? Set the steps per mm based on the output, not the input. Your steps/mm will be "spot-on" when it gives you the correct line width. At least at the print speed and acceleration you're using for the test. Some controller firmware has multiple settings to compensate for nonlinearities in extrusion that result from changes in speed that result from print speed, acceleration, and jerk settings.

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

Gotcha. Thanks for the feedback.

So, I have been doing wrong for 6 years, now i'm confused. I always have read that you mark solid filament, for example this manual: [all3dp.com] , so why is so extended to calibrate input instead output? Just beccause is it easy?

to be honest, on reprap spanish comunity 6 years ago, they told me to remove hotend, mark filament and send 100 mm to extrude. is it an aproximation?

Do you have done at this way always? (I refer to measure output).

thanks in advance

... measuring the filament entry length is easy, but didn't fit the extruder output exactly!

The output varies with temperature, extruding speed and variance in entry filament diameter -- so better kalibrate with printing test-parts ...

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Viktor
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Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

the 100mm filament test is just stage one to get a ball park figure...

You then have to adjust this to to get an optimum value.

I have always found this process to work well: [reprap.org]
Pay attention to the fine e-steps calibration.

Back in the old days I used to measure every spool of filament, calculate the average diameter, and use that value for volumetric extrusion set at print time. It's probably still a good idea to do that when you're calibrating- garbage in-garbage out. These days even no-name filament brands have figured out how to control the filament diameter and variation so well I don't bother with volumetric extrusion any more.

If you're really obsessed with it, use a Duet board and start adjusting all the nonlinear tweaks.

Final hint: if you have to tweak extrusion on the fly, you probably need to do a better job calibrating the extrusion.

Edited 1 time(s). Last edit at 02/29/2020 07:17AM by the_digital_dentist.

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

Thanks guys for your attention. It's a pleasure to belong to this community.

I'm checking now all tips.

I'm not obsessed with that, I have an ulticampy (ultimaker kind) and I have some tolerance I can live with it. Anyways I always like to learn more.

The printer has no way of knowing what line width it is outputting. If you set the width to 0.5 you are asking it to scale its model of the flow to get that width.
One possibility is your Z steps are wrong. The model calculates based on the dimension you have for layer height. If your Z steps per mm is to large, the layer height will be larger than the model and you can get under extrusion. The obvious test is to set a z height for movement and measure it. You probably already calibrated this. Although if your layer height is to high (over 0.35mm) you may start to have difficulties.
Whats interesting is that you have a wall thickness less than the nozzle diameter. That's tough to do. Maybe there is a lot of shrinkage in your material.