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first_layer_squish.md

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First Layer Squish

I'm going to call it "squish" to be unambiguous. "Z offset" and "z height" can be conflated with other concepts.

  • ⚠️ This section assumes that you have already done a rough 📄Z offset calibration.

  • ⚠️ This section also assumes that you have a consistent first layer squish, both across the entire build surface and between prints.

Method

1) Set your first layer height to 0.25 or greater (in my opinion).

  • Thicker first layer heights are less sensitive and easier to maintain, especially on larger printers where first layer consistency can be a challenge.

  • Aside from that, this is personal preference.

2) Scatter square patches around your bed in your slicer.

  • See the 📄test_prints folder.

    • Choose a patch that matches your first layer height.
      (First_Layer_Patch-0.25mm.stl if you chose to follow step 1)

    • Tip: in PS/PSS, you can right-click the "arrange" button and set the distance to a large value.*
    • image
      * To exceed 100mm, either click the edit button on the right side, or ctrl+click the bar.

3) Set your first layer 📄line width to 120% or greater.

4) Start the print. While it is printing, 📄live adjust z.

  • This can be done via g-codes/macros, LCD, or via web. I find it easiest to sit in front of the printer and fine-tune with the LCD.

Examples

In these examples, the third square is closest.
There are real-life print examples in the next section.

Note: When I refer to "gaps", I mean where you can see between/through the extrusion lines.

If you can see any light (excluding pinholes at the perimeter), or the next layer on real prints, then you need more squish.

  • Smooth Build Surface

    • Top Surface

      • You don't want too many ridges/hairs on top.
        • It's normal to have a little bit of this near the corners, or in small print areas.
      • You shouldn't see any gaps* between the lines.
        • It's fine to have some very small pinholes where the infill meets the perimeters.
      • NOTE: Upon review, somewhere between square 3 and 4 is closer to ideal.

    • Bottom Surface

      • You should not have any gaps between the lines.
      • You should still be able to clearly see the lines at the center. They should not be fading or invisible.
        • It's normal for the lines to fade a bit near the edges/corners.
      • NOTE: Upon review, somewhere between square 3 and 4 is closer to ideal.

  • Textured Build Surface

    • Top Surface
      • Follow the same guidance as for smooth build surfaces (above). You can see hairs/lumps with too much squish, and gaps with not enough squish.
    • Bottom Surface
      • The lines will not be as visible as on a smooth build surface.
        • Note: this doesn't mean they should be invisible.
      • As with smooth build surfaces, you should not have any gaps between the lines.
      • With textured, it's a bit easier to tell squish using the top surface rather than the bottom surface.

5) Once you are happy with your squish, cancel the print and then save your new offset with one of the below methods:

  • Dedicated Z Endstop:
    (With dedicated Z endstops. Stock V0/V2/Trident are set up this way)

    • Enter Z_OFFSET_APPLY_ENDSTOP*
      • This will apply your new offset to your stepper_z's position_endstop.
    • Enter SAVE_CONFIG.

  • Virtual Z Endstop:
    (When using the probe as the Z endstop. Stock Switchwire and Legacy are set up this way)

    • Enter Z_OFFSET_APPLY_PROBE*
      • This will apply your new offset to your probe's z_offset.
    • Enter SAVE_CONFIG.

  • Klicky Auto Z Calibration:
    (This is a mod, it uses Klicky AND nozzle endstop to automatically baby step before each print. See 📄here for more information.)

    • Manually adjust your switch_offset based on how much extra you had to baby step.
      • Higher value = more squish
      • Lower value = less squish
    • If your value is straying too far from your switch's theoretical switch_offset (usually 0.5), there may be another issue at play. Values of 0.4-0.6 are fairly normal (for the standard Omron switches).

* Requires a semi-recent version of Klipper.

Print Examples

You should still clearly be able to see the lines. If it's completely smooth, your squish is too much. If you see gaps between the lines, you need more squish.

Good Squish

Too Much Squish

  • Can't see any lines, or the lines are starting to fade (smooth PEI):

  • Wavy patterns appear:

Not Enough Squish

  • There are gaps between the lines (you can see through to the next layer):

    Further Fine-Tuning

    • If you have a gappy second layer (or first few layers), it may indicate that you need a little more squish.
      • There are other possible causes for this issue (like not heat soaking for long enough, or flow dropoff)
    • This cube needs just a tiny bit more squish.
      You can see very slight gapping / shadows between the perimeters and some areas of the infill. The corners are also starting to pull away a bit.
    • Better!

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