updated documentation

docs/macros/axis_tuning.md

@@ -73,23 +73,23 @@ That said, interpreting Input Shaper graphs isn't an exact science. While we can
 
 ### Good graphs
 
-These two graphs are considered good and is what you're aiming for. They each display a single, distinct peak that stands out clearly against the background noise. Note that the main frequencies of the X and Y graph peaks differ. This variance is expected and normal, as explained in the last point of the [useful facts and myths debunking](#useful-facts-and-myths-debunking) section.
+These two graphs are considered good and is what you're aiming for. They each display a single, distinct peak that stands out clearly against the background noise. Note that the main frequencies of the X and Y graph peaks differ. This variance is expected and normal, as explained in the last point of the [useful facts and myths debunking](#useful-facts-and-myths-debunking) section. The spectrogram is clean with only the resonance diagonals. Note that a fan was running during the test, as shown by the purple vertical line (see section [fan behavior](#fan-behavior)).
 
 | Good X graph | Good Y graph |
 | --- | --- |
-| ![](../images/shaper_graphs/low_canbus_solved.png) | ![](../images/shaper_graphs/reso_good_y.png) |
+| ![](../images/shaper_graphs/good_x.png) | ![](../images/shaper_graphs/good_y.png) |
 
 ### Low frequency energy
 
-These graphs have some low frequency energy (signal near 0 Hz) on a rather low maximum amplitude (around 1e2 or 1e3). This means that there is some binding, rubbing or grinding during movements: basically, something isn't moving freely. Minor low frequency energy in the graphs might be due to a lot of issues such as a faulty idler/bearing or an overly tightened carriage screw that prevent it to move freely on its linear rail, ... However, major low frequency energy suggest more important problems like improper belt routing (the most common), or defective motor, ...
+These graphs have low frequency (near 0 Hz) at a rather low maximum amplitude (around 1e2 or 1e3) signal. This means that there is some binding, rubbing, or grinding during motion: basically, something isn't moving freely. Minor low frequency energy in the graphs can be due to many problems, such as a faulty idlers/bearing or an over-tightened carriage screw that prevents it from moving freely on its linear rail, a belt running on a bearing flange, ... However, large amounts of low frequency energy indicate more important problems such as improper belt routing (the most common), or defective motor, ...
 
 Here's how to troubleshoot the issue:
   1. **Belts Examination**:
      - Ensure your belts are properly routed.
      - Check for correct alignment of the belts on all bearing flanges during movement (check them during a print).
      - Belt dust is often a sign of misalignment or wear.
-  2. **Toolhead behavior on CoreXY printers**: With motors off and the toolhead centered, gently push the Y-axis front-to-back. The toolhead shouldn't move left or right. If it does, one of the belts might be obstructed and requires inspection to find out the problem.
-  3. **Gantry Squareness**:
+  1. **Toolhead behavior on CoreXY printers**: With motors off and the toolhead centered, gently push the Y-axis front-to-back. The toolhead shouldn't move left or right. If it does, one of the belts might be obstructed and requires inspection to find out the problem.
+  1. **Gantry Squareness**:
      - Ensure your gantry is perfectly parallel and square. You can refer to [Nero3D's de-racking video](https://youtu.be/cOn6u9kXvy0?si=ZCSdWU6br3Y9rGsy) for guidance.
      - After removing the belts, test the toolhead's movement by hand across all positions. Movement should be smooth with no hard points or areas of resistance.
 
@@ -101,9 +101,9 @@ Here's how to troubleshoot the issue:
 
 Such graph patterns can arise from various factors, and there isn't a one-size-fits-all solution. To address them:
   1. A wobbly table can be the cause. So first thing to do is to try with the printer directly on the floor.
-  2. Ensure optimal belt tension using the [`BELTS_SHAPER_CALIBRATION` macro](./belts_tuning.md).
-  3. If problems persist, it might be due to an improperly squared gantry. For correction, refer to [Nero3D's de-racking video](https://youtu.be/cOn6u9kXvy0?si=ZCSdWU6br3Y9rGsy).
-  4. If it's still there... you will need to find out what is resonating to fix it. You can use the `EXCITATE_AXIS_AT_FREQ` macro to help you find it.
+  1. Ensure optimal belt tension using the [`BELTS_SHAPER_CALIBRATION` macro](./belts_tuning.md).
+  1. If problems persist, it might be due to an improperly squared gantry. For correction, refer to [Nero3D's de-racking video](https://youtu.be/cOn6u9kXvy0?si=ZCSdWU6br3Y9rGsy).
+  1. If it's still there... you will need to find out what is resonating to fix it. You can use the `EXCITATE_AXIS_AT_FREQ` macro to help you find it.
 
 | Two peaks | Single wide peak |
 | --- | --- |
@@ -119,23 +119,30 @@ Using CANBUS toolheads with an integrated accelerometer chip can sometimes pose
 
 ### Toolhead or TAP wobble
 
-The [Voron TAP](https://github.com/VoronDesign/Voron-Tap) can introduce anomalies to input shaper graphs, notably on the X graph. Its design with an internal MGN rail introduces a separate and decoupled mass, leading to its own resonance, typically around 125Hz. Combatting this can be pretty challenging, but using premium components and a careful assembly can help mitigate the issue. Ensure you employ a good quality and well-preloaded TAP MGN rail for optimal assembly stiffness, coupled with genuine and strong N52 magnets (avoid lower-quality N35 or N45 substitutes often found on chinese marketplaces). Prioritize careful assembly and consider using the TAP Rev8 version or above.
+The [Voron TAP](https://github.com/VoronDesign/Voron-Tap) can introduce anomalies to input shaper graphs, notably on the X graph. Its design with an internal MGN rail introduces a separate and decoupled mass, leading to its own resonance, typically around 125Hz.
 
-Additionally, without a Voron TAP, small 125hz peaks can sometimes tie back to the toolhead itself. Common culprits include loosely fitted screws or a bad quality X linear MGN axis that can have some play in the carriage, leading to slight toolhead wobbling. This is often represented as a Z component in the graphs.
+Small 125Hz peaks are also most often due to the toolhead itself, since most toolheads are about the same mass. Common culprits include loose screws or a bad quality X linear MGN axis that can have some play in the carriage, causing the toolhead to wobble slightly. This is often shown as a Z component in the graphs and can be amplified by the bowden tube or an umbilical that applies some forces on top of the toolhead.
 
-If your graph shows this kind of anomalies, begin by disassembling the toolhead up to the X carriage. Check for any looseness, then reassemble, ensuring everything is tightened properly for a rigid assembly. Also, don't forget to check your extruder and validate its assembly as well. Finally, ensure you have some filament loaded during measurements to prevent extruder gear vibrations.
+If your graph shows this kind of anomalies:
+  1. Start by looking at the bowden tube and umbilical to make sure they are not exerting excessive force on the toolhead. You want them to create no drag or as little drag as possible.
+  1. If that's not enough, continue disassembling the toolhead down to the X carriage. Check for any loose or cracked parts, then reassemble, making sure everything is tightened properly for a rigid assembly.
+  1. When using TAP, this can be quite a challenge to combat, but using quality components and careful assembly can help mitigate the problem. In particular, be sure to use a well-preloaded TAP MGN rail for maximum rigidity, coupled with genuine and strong N52 magnets that are properly seated and not loose.
+  1. Don't forget to check your extruder and make sure you have some filament loaded during the measurements to avoid extruder gear vibration.
 
-| TAP wobble problem | TAP wobble problem partially mitigated<br/>Or toolhead wobbling |
+| TAP wobble problem | TAP wobble problem mitigated<br/>Or toolhead wobbling |
 | --- | --- |
 | ![](../images/shaper_graphs/TAP_125hz.png) | ![](../images/shaper_graphs/TAP_125hz_2.png) |
 
-### Unbalanced fan
+### Fan behavior
 
-The presence of an unbalanced or badly running fan can be directly observed in the graphs. While you should let the toolhead fans off during the final IS tuning, you can use this test to validate their correct behavior: an unbalanced fan usually add some very thin peak around 100-150Hz that disapear when the fan is off. Also please note that an unbalanced fan constant frequency is manifested as a vertical line on the bottom spectrogram.
+The presence of an unbalanced or poorly running fan can be directly observed in the spectrogram:
+  1. A properly running fan can be seen as a vertical purple line on the spectrogram that doesn't shine too much. This is perfectly normal because it's running at a constant speed (i.e. constant frequency) throughout the test. The purple color means that its vibration energy is quite low and should not cause any problems. There are no corresponding peaks on the top graph.
+  1. When the vertical line on the spectrogram starts to become yellowish, pay special attention to the top graph to see if there is a corresponding peak. In the example from the middle below, the fan is in the limit with a very small bump corresponding to it. So it may or may not cause trouble... Do some test prints and look for VFAs, if you find some you may want to replace the fan.
+  1. If the vertical line is bright orange/yellow, there will most likely be a corresponding thin but high peak on the top graph. This fan is out of balance, producing bad vibrations and needs to be replaced.
 
-| Unbalanced fan running | Unbalanced fan off |
-| --- | --- |
-| ![](../images/shaper_graphs/unbalanced_fan_on.png) | ![](../images/shaper_graphs/unbalanced_fan_off.png) |
+| Healthy fan running | Fan start to be problematic | Fan need to be changed |
+| --- | --- | --- |
+| ![](../images/shaper_graphs/fan_notproblematic.png) | ![](../images/shaper_graphs/fan_maybeproblematic.png) | ![](../images/shaper_graphs/fan_problematic.png) |
 
 ### Noisy accelerometer
 
@@ -153,7 +160,7 @@ Finally, please note that LIS2DW are known to add a small offset all over the to
 
 The depicted graphs are challenging to analyze due to the overwhelming noise across the spectrum. Such patterns are often associated with an improperly assembled and non-squared mechanical structure. To address this:
   1. Refer to the [Low frequency energy](#low-frequency-energy) section for troubleshooting steps.
-  2. If unresolved, consider disassembling the entire gantry, inspect the printed and mechanical components, and ensure meticulous reassembly. A thorough and careful assembly should help alleviate the issue. Measure again post-assembly for changes.
+  1. If unresolved, consider disassembling the entire gantry, inspect the printed and mechanical components, and ensure meticulous reassembly. A thorough and careful assembly should help alleviate the issue. Measure again post-assembly for changes.
 
 Also please note that for this kind of graphs, as they are mainly consisting of noise, Klipper's algorithm recommendations must not be used and will not help with ringing. You will need to fix your mechanical issues instead!