Complete EM misconception section, various other tweaks

articles/determining_max_volumetric_flow_rate.md

@@ -98,18 +98,21 @@ If you use the CNC Kitchen method, you may need to temporarily increase your `m
 
 You will follow a similar process to extruder calibration. 
 
-1. Heat your hotend. 
+1. Open your printer.cfg and find the `[extruder]` section. Set `max_extrude_only_distance` to 101 or higher and `RESTART`.\
+*(+1 just helps avoid rounding error issues)*
+
+2. Heat your hotend. 
  - :bulb: Temperature has a large impact on max flow rates.
 
  - If you are going for absolute maximum flow rates, you may want to bump your temperatures. Some people print ABS at 250-270C for this reason. This is a tradeoff, however, as it can also cause oozing, overheating, or material degradation at slower speeds. I personally run higher temperatures for fast functional prints, and lower my temperatures (and volumetric limit) for more decorative prints.
 
-2. Extrude a little bit to ensure your E motor is energized and holding.
+3. Extrude a little bit to ensure your E motor is energized and holding.
 
-3. Mark a 100mm length of filament.
+4. Mark a 100mm length of filament.
  - Use a bit of tape. Stick it at the 100mm mark on a ruler and transfer it to the filament. Using tape makes it quick & easy to mark between tests.
  - Since this is a rough test, you can also measure at the reverse bowden inlet/spool. Just pull the slack out of the filament when marking and when measuring.
 
-4. Extrude at increasing speeds. 
+5. Extrude at increasing speeds. 
  - At each interval, measure to ensure that ~100mm entered the extruder.
  - The gcode uses mm/min, **not** mm/sec, so multiply your desired speed by 60.
  - For example, the gcode to extrude at 5mm/sec is:
@@ -118,18 +121,22 @@ You will follow a similar process to extruder calibration.
  G1 E100 F300 ; Extrude 100mm at 300mm/min (5mm/sec)
  ```
 
-5. Keep increasing speeds and extruding until it starts dropping below 100mm\*. This is your max flow rate. 
+6. Keep increasing speeds and extruding until it starts dropping below 100mm\*. This is your max flow rate. 
 
  - \* See the [:pushpin: "Flow Dropoff"](#flow-dropoff) section and determine your personal dropoff tolerance. I personally try to stay under 2-3% dropoff.
 
-6. Convert the maximum extrusion speed you found to volumetric speed using the [:pushpin: formulas](#formulas).
+7. Convert the maximum extrusion speed you found to volumetric speed using the [:pushpin: formulas](#formulas).
  - Example: You reached your personal [:pushpin: flow dropoff](#flow-dropoff) tolerance of 2% at **F600** extrusion speed. 
  - 600mm/min / 60 = 10mm/sec. 
  - 10mm/sec * 2.4 = **Flow rate of 24mm<sup>3</sup>/sec**.
 
-7. Try extruding a longer distance (say 200-300mm). Ensure that your printer can sustain this flow rate.
+8. Try extruding a longer distance (say 200-300mm). Ensure that your printer can sustain this flow rate.
+
+9. Choose a **slightly lower value than your results**.
+ - Real-world flow rates will be a bit less than your synthetic results. 
+ - Real prints have more resistance to overcome - they have to press against the previous layer, whereas we only tested an ideal scenario with zero resistance.
 
-8. Set your new value in your slicer.
+10. Set your new value in your slicer.
  - :warning: **In Prusa Slicer, this *must* be managed in the filament settings.** The setting in the "auto speed" section only applies in specific circumstances in PS.
 
  - In SuperSlicer, you should set the volumetric limit in your print profile to a lower "default" value. 

articles/first_layer_squish.md

@@ -25,7 +25,7 @@ I'm going to call it "squish" to be unambiguous. "Z offset" and "z height" can b
 >  - If using probe as endstop (also known as "virtual endstop"), see [:page_facing_up: here](https://www.klipper3d.org/Probe_Calibrate.html#calibrating-probe-z-offset).
 >  - If using dedicated Z endstop, follow the same instructions but use `Z_ENDSTOP_CALIBRATE` instead of `PROBE_CALIBRATE`.
 >  - ![]({{ "/assets/img/voron_small.png" | absolute_url }}) **Vorons**: See [:page_facing_up: here](https://docs.vorondesign.com/community/howto/120decibell/z_endstop_configuration.html#initial-calibration).
-> - ![]({{ "/assets/img/marlin_small.png" | absolute_url }}) **Marlin**: Baby stepping must be [:page_facing_up: enabled in firmware](https://github.com/MarlinFirmware/Marlin/blob/bugfix-2.1.x/Marlin/Configuration_adv.h#L2057). (Most printers have it enabled by default).
+> - ![]({{ "/assets/img/marlin_small.png" | absolute_url }}) **Marlin**: Baby stepping must be [:page_facing_up: enabled in firmware](https://marlinfw.org/docs/configuration/configuration.html#babystepping). (Most printers have it enabled by default).
 
 ![]({{ "/assets/img/voron.png" | absolute_url }}) **Vorons**: See the [:page_facing_up: Thermal Drift](./troubleshooting/first_layer_squish_consistency_issues/thermal_drift.md) article, **even if you are not having any issues.** Thermal drift is in important thing to know about with larger enclosed printers.
 

articles/index_troubleshooting.md

@@ -46,7 +46,7 @@ has_children: true
 - :warning:Thermal Drift
 - First Layer Conistency
 - Squish Consistency (Between Prints)
-[![](/images/first_layer_squish/FirstLayer-Squares-1.png)](/images/first_layer_squish/FirstLayer-Squares-1.png){:target="_blank"}
+[![](./images/first_layer_squish/FirstLayer-Squares-1.png)](./images/first_layer_squish/FirstLayer-Squares-1.png){:target="_blank"}
 
 ## [Layer Shifting](./troubleshooting/layer_shifting.md) 
 - Mechanical

articles/misconceptions.md

@@ -21,7 +21,46 @@ nav_order: 9
 
 This is just a list of things that I often see floating around that are, in my opinion, misconceptions or bad advice.
 
-## Two 0.4mm Perimeters = 0.8mm
+## Tuning Extrusion Multiplier By Measuring 1-2 Cube Walls
+
+When measuring two walls, you run into the [:pushpin: issue described above](#two-04mm-perimeters--08mm). Two walls does **NOT equal line width * 2**!
+
+In both cases, you are also measuring **layer wobble and inconsistent extrusion**, which all printers and filaments have in some degree. You will always be measuring the bit that sticks out most.
+
+{% comment %} 
+
+Please excuse the upcoming vomit I used to bodge this table's widths/spacing
+
+{% endcomment %} 
+
+
+| <br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;**Layer Wobble** &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<br><br> | <br>**Inconsistent Extrusion /**<br>&nbsp;&nbsp;&nbsp;&nbsp;**Filament Diameter Fluctuations**&nbsp;&nbsp;&nbsp;&nbsp;<br><br> |
+| :-----------: | :-----------: |
+| <br>[![](./images/misconceptions/layer_wobble_marked.png)](./images/misconceptions/layer_wobble_marked.png){:target="_blank"}<br><br> | [![](./images/misconceptions/extrusion_inconsistency_marked.png)](./images/misconceptions/extrusion_inconsistency_marked.png){:target="_blank"} |
+
+- Your measurement will basically **always** be a bit too large because of this!
+
+- Additionally, when making small measurements like this, **small errors become big errors**:
+
+ - For example, the difference between 0.42mm and 0.4mm, an only 0.**0**2mm difference, is about **5%**.
+
+ - **That's a huge adjustment!** It's very easy to measure 0.02mm off - due to consumer-grade calipers, where you measure, how much layer wobble you have, how much pressure you use, the diameter fluctuations of your filament, what you ate for breakfast, etc...
+
+  - You should always make dimensional adjustments based on **larger objects**, where minor errors are proportionally much smaller.*
+
+  - *I actually don't like adjusting extrusion multiplier based on measurements at all.\
+  I don't think it makes sense to have a gappy or rough print just to compensate for dimensions.\
+  See [:page_facing_up: here](./extrusion_multiplier.md) for how I do it - tune for a perfect top surface, and then adjust slicer settings like shrinkage compensation and horizontal expansion, as needed, to tweak dimensions.*
+
+**This method is, much to my chagrin, extremely prevalent:**
+- [https://teachingtechyt.github.io/calibration.html#flow](https://teachingtechyt.github.io/calibration.html#flow)
+- [https://help.prusa3d.com/article/extrusion-multiplier-calibration_2257](https://help.prusa3d.com/article/extrusion-multiplier-calibration_2257)\
+Even Prusa recommends it!
+- [https://3dprintbeginner.com/flow-rate-calibration/](https://3dprintbeginner.com/flow-rate-calibration/)
+
+<sup>Send help. I'm going insane.</sup>
+
+## "Two 0.4mm Perimeters = 0.8mm"
 
 The title is just an example, this applies to any line width or perimeter count.
 
@@ -51,69 +90,94 @@ You would put a **spacing** *(or "width & spacing combo" for external perimeters
 - Then two lines would equal 0.8mm, three lines would equal 1.2mm, and so on.
 
 
-## Tuning Extrusion Multiplier By Measuring 1-2 Cube Walls
+## "You Shouldn't Tune Extrusion Multiplier, The Slicer Knows Best"
+..."e-steps / extruder calibration is all you need to do"
 
-When measuring two walls, you run into the [:pushpin: issue described above](#two-04mm-perimeters--08mm). Two walls does **NOT equal line width * 2**!
+<sup>This section was created by heavily referencing [:page_facing_up: Slic3r Flow Math documentation](https://manual.slic3r.org/advanced/flow-math). Prusa Slicer is a fork of Slic3r, and SuperSlicer is a fork of Prusa Slicer. They both use this math as their basis. Other major slicers also use the same math.</sup>
 
-In both cases, you are also measuring **layer wobble and inconsistent extrusion**, which all printers and filaments have in some degree. You will always be measuring the bit that sticks out most.
+In a perfect world, the slicer would be perfect, and know exactly how much plastic to extrude. But - nothing can ever be simple, can it?
 
-{% comment %} 
+### The Assumptions
 
-Please excuse the upcoming vomit I used to bodge this table's widths/spacing
+Slicers make some assumptions.\
+The first major assumption they make is that extrusion comes out in this exact shape:
+- [![](./images/misconceptions/slic3r_cross-section.png)](./images/misconceptions/slic3r_cross-section.png){:target="_blank"}\
+[Source](https://manual.slic3r.org/advanced/flow-math)
 
-{% endcomment %} 
+- The cross-sectional area of this shape is calculated using the formula shown.\
+To calculate the volume of plastic needed for a given extrusion line, this cross-sectional area is then multiplied by the length.
 
+Based on the first assumption, a second assumption is then made.
 
-| <br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;**Layer Wobble** &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<br><br> | <br>**Inconsistent Extrusion /**<br>&nbsp;&nbsp;&nbsp;&nbsp;**Filament Diameter Fluctuations**&nbsp;&nbsp;&nbsp;&nbsp;<br><br> |
-| :-----------: | :-----------: |
-| <br>[![](./images/misconceptions/layer_wobble_marked.png)](./images/misconceptions/layer_wobble_marked.png){:target="_blank"}<br><br> | [![](./images/misconceptions/extrusion_inconsistency_marked.png)](./images/misconceptions/extrusion_inconsistency_marked.png){:target="_blank"} |
+- If the extrusion lines did not overlap, you would get voids (highlighted).
 
-- Your measurement will basically **always** be a bit too large because of this!
+ - [![](./images/misconceptions/voids.png)](./images/misconceptions/voids.png){:target="_blank"}
 
-- Additionally, when making small measurements like this, **small errors become big errors**:
+ - To fill this space, the lines are instead set to overlap a bit. The colliding plastic is forced out, with the intent of filling these voids.\
+ The assumption made is that we need to overlap the paths so that the overlapping area equals the void area (of these *theoretical* cross-sections):
+ - [![](./images/misconceptions/overlap_voids.png)](./images/misconceptions/overlap_voids.png){:target="_blank"}
 
- - For example, the difference between 0.42mm and 0.4mm, an only 0.**0**2mm difference, is about **5%**.
+This all provides a convenient and "good enough" model - but it of course ignores countless variables and unknowns (internal stresses, viscosity, extrusion speed, temperatures, the size and location of the unavoidable air gaps, etc.)
 
- - **That's a huge adjustment!** It's very easy to measure 0.02mm off - due to consumer-grade calipers, where you measure, how much layer wobble you have, how much pressure you use, the diameter fluctuations of your filament, what you ate for breakfast, etc...
+### A Bit of Guesswork
+This is an excerpt from the Slic3r documentation. 
+- [![](./images/misconceptions/slic3r_spacing_text.png)](./images/misconceptions/slic3r_spacing_text.png){:target="_blank"}\
+[Source](https://manual.slic3r.org/advanced/flow-math)
+ - As you can see, there was basically a bit of guesswork done, and it was chosen to lean on the side of **overextrusion**.
 
-  - You should always make dimensional adjustments based on **larger objects**, where minor errors are proportionally much smaller.*
+### Demonstration
 
-  \* *I actually don't like adjusting extrusion multiplier based on measurements at all. But that's more debatable.\
- In my opinion, it's best to print an object with 100% solid infill and tune extrusion multiplier until it fills perfectly without going over. See [:page_facing_up: here](./extrusion_multiplier.md) for specific instructions. Then adjust things like shrinkage compensation in the slicer.\
- I don't think it makes sense to have a gappy or rough print just to compensate for dimensions.*
+These examples will use a 0.4mm nozzle, and 0.2mm layer height.
 
-**This method is, much to my chagrin, extremely prevalent:**
-- [https://teachingtechyt.github.io/calibration.html#flow](https://teachingtechyt.github.io/calibration.html#flow)\
-You may notice this guide popping up a lot on this page, as I add more sections....
-- [https://help.prusa3d.com/article/extrusion-multiplier-calibration_2257](https://help.prusa3d.com/article/extrusion-multiplier-calibration_2257)\
-Even Prusa recommends it!
-- [https://3dprintbeginner.com/flow-rate-calibration/](https://3dprintbeginner.com/flow-rate-calibration/)
+This shape is actually *impossible* at layer widths below `nozzle size + layer height`.
 
-<sup>Send help. I'm going insane.</sup>
+- At the very common line width of 0.4mm (100%), that assumption would look like this:
+
+ - [![](./images/misconceptions/0.4mm_0.2mm.png)](./images/misconceptions/0.4mm_0.2mm.png){:target="_blank"}
+
+ - See the problem?\
+ At most common line widths, **this assumption would mean that the extrusion does not even cover the nozzle orifice.** It's **physically impossible** for the filament to "jump" out of the nozzle and create that gap!
+
+- The only way to cover that orifice would be to increase your extrusion width to `nozzle size + layer height` - in this example, that would be 0.6mm (150%). 
 
+ - [![](./images/misconceptions/0.6mm_0.2mm.png)](./images/misconceptions/0.6mm_0.2mm.png){:target="_blank"}
+ - Most people don't use line widths this thick, and certainly not for *all* features.
 
-## Tuning Extrusion Multiplier is a Bodge
+- To contribute some of my own speculation, I would think that a "0.4mm" (100%) line would look something a bit more like this:
+ - [![](./images/misconceptions/cross_section_speculation.png)](./images/misconceptions/cross_section_speculation.png){:target="_blank"}
+ - Just to reinforce: this is **only speculation**. I tried to show some die swell, and to consider that the nozzle orifice must be covered.
+ - If this were true, that would likely mean more material at the top than at the bottom, and would create larger air gaps at the bottom.
 
-The gap between theory and reality is often larger in reality than it is in theory.
+To sum up - we really can't predict **exactly** what the cross section will look like. We also can't say exactly where there will be inevitable air gaps, and how large they will be.
 
-More info to come...
+Because of all of this, we can't predict **exactly** how much plastic to extrude. Even if we did know the exact cross section through observation, it could entirely change as soon as you change any one variable. 
+
+Slicers just use a convenient and "close enough" model to predict it. 
+
+That can only mean one thing - **we have to tweak the extrusion multiplier a bit** based on real-world results, the properties of our specific material, our own temperatures and speeds, and all of the other unknown variables - not just implicitly trust that the slicer's flow model is perfect.
+
+Sorry Angus (Maker's Muse), I love your videos but I have to [:page_facing_up: disagree with you here](https://youtu.be/YPAXeBuq9qU?t=869)!
+
+## "Never Use Cooling for ABS"
+While this is valid advice for unenclosed printers, it's not a universal rule.
+
+ABS often needs some cooling. In warmer enclosures, it can need *significant* cooling.\
+That's actually one of the advantages of a good enclosure - that you *can* use cooling!
+
+See [:page_facing_up: Cooling and Layer Times](./cooling_and_layer_times.md).
 
 ## Using Paper to Set Z Offset
 
 It's fine to get a very rough starting point - but paper is otherwise not to be used for absolute measurements, only relative ones.
 
-More info to come...
+*(More info to come...)*
 
 
 {% comment %} 
 
-## "You Should use 100% Extrusion Multiplier"
-
-- https://youtu.be/YPAXeBuq9qU?t=869
-
 ## Calibrating Belted Axis Steps
 
-- https://youtu.be/YPAXeBuq9qU?t=166 *(you might notice that this is the third time this video has appeared on this list...)*
+- https://youtu.be/YPAXeBuq9qU?t=166
 - https://teachingtechyt.github.io/calibration.html#xyzsteps
 - https://all3dp.com/2/how-to-calibrate-a-3d-printer-simply-explained/
 - https://www.3dbeginners.com/how-to-calibrate-a-3d-printer/

articles/pressure_linear_advance/introduction.md

@@ -25,7 +25,7 @@ grand_parent: Tuning
 
 {: .prereqs}
 > - You should [:page_facing_up: calibrate your extruder](https://docs.vorondesign.com/build/startup/#extruder-calibration-e-steps) first.
-> - ![]({{ "/assets/img/marlin_small.png" | absolute_url }}) **Marlin**: Linear advance must be [:page_facing_up: enabled in firmware](https://github.com/MarlinFirmware/Marlin/blob/bugfix-2.1.x/Marlin/Configuration_adv.h#L2104). Not all printers have it enabled by default. 
+> - ![]({{ "/assets/img/marlin_small.png" | absolute_url }}) **Marlin**: Linear advance must be [:page_facing_up: enabled in firmware](https://marlinfw.org/docs/configuration/configuration.html#linear-advance). Not all printers have it enabled by default. 
 
 ---
 <details open markdown="block">

articles/troubleshooting/bulging.md

@@ -39,7 +39,10 @@ It can also help with extrusion / layer consistency.
 - [![](./images/bulging/external_first_1.png)](./images/bulging/external_first_1.png){:target="_blank"} 
 - [![](./images/bulging/external_first_2.png)](./images/bulging/external_first_2.png){:target="_blank"} 
 
-- :warning: This can negatively affect *extreme* overhangs, and occasionally cause some other oddities, so just keep it in mind when troubleshooting. It's generally okay for daily use, though.
+- :warning: With external perimeters first, it's especially important to ensure that you have a good [:page_facing_up: stepover](../stepover.md) for your overhangs. It's less resistant to poor stepover.
+
+ - External perimeters first can still negatively affect *extreme* overhangs, and occasionally cause some other oddities, so just keep it in mind when troubleshooting. It's generally okay for daily use, though.
+
  - [![](./images/bulging/external_first_3.png)](./images/bulging/external_first_3.png){:target="_blank"} 
 
 ## Bulging Layers