Fine‐Tuning Z‐Offset with Test Prints - Phil1988/FreeDi GitHub Wiki

What are we doing now?

After completing the coarse Z-offset calibration, it's time to fine-tune it for perfect first layer adhesion. This method is much more accurate than the paper test because you can see and adjust the actual print quality in real-time.

⚠️ Quick Context: This is the fine-tuning step that perfects your Z-offset. Make sure you've completed coarse Z-offset calibration first. This method uses live adjustment (babystepping) while printing a test pattern.

What is Fine-Tuning?

The paper test gets you "close enough," but it's not perfect. Fine-tuning uses an actual print to dial in the exact Z-offset by observing how the filament lays down and making live adjustments until it looks perfect.

Time required: ~5-15 minutes (one test print)

Prerequisites

Step 1: Locate the Pre-Sliced Test File

FreeDi includes pre-sliced Z-offset calibration files for each printer model. These files print a single-layer test pattern that's perfect for fine-tuning.

Finding the Test File

After installation (if you used the on-screen wizard), the calibration files are automatically placed in /home/mks/printer_data/gcodes/.

Option A: Via Mainsail

Option B: Via Display File Manager

If you don't have the files: Download them from the FreeDi GitHub repository and upload them to your printer via Mainsail.

Step 2: Start the Test Print

  1. Select the calibration file for your printer model
  2. Start the print
  3. Watch closely as the first layer begins printing

Note: The test print is designed to give you enough time to make adjustments before it finishes. Stay near the printer and keep your eyes on the first layer!

Step 3: Observe and Adjust with Babystepping

While the print is running, observe the first layer quality and make live adjustments using babystepping.

Accessing Babystepping

On the print job screen, you'll see an icon to access babystepping:

[Screenshot placeholder: Print job screen with babystepping icon highlighted]

Tap the icon to open the adjustment menu:

[Screenshot placeholder: Babystepping adjustment screen showing increment buttons]

Step 4: What to Look For

Nozzle Too Close (Z-offset too negative)

Visual signs:

  • Filament is squished flat with no texture
  • Material pushed to the sides creating ridges
  • Lines merge together completely (no gaps visible)
  • "Elephant's foot" effect (bottom layer wider than it should be)
  • Translucent or very thin appearance

What to do: Increase Z-offset (make it less negative) using babystepping – tap the + button in small increments

Nozzle Too Far (Z-offset too positive)

Visual signs:

  • Lines don't stick to the bed
  • Visible gaps between lines
  • Lines are round instead of flat
  • Poor adhesion (lines lift or curl)
  • Rough, textured surface

What to do: Decrease Z-offset (make it more negative) using babystepping – tap the - button in small increments

Perfect Z-Offset ✅

Visual signs:

  • Smooth, even surface with slight texture
  • Lines touch but are still individually visible when looking closely
  • No gaps between lines
  • Good adhesion to the bed
  • Slight glossy appearance (not matte, not mirror-shiny)
  • Consistent thickness across the entire print

This is your target! Once you see this, stop adjusting.

Step 5: Save Your Z-Offset

After the print completes, you'll be taken to the "Print Completed" screen.

Important: If you made any Z-offset adjustments during the print, a "Save Z-Offset" button will appear on this screen.

[Screenshot placeholder: Print completed screen with "Save Z-Offset" button]

Tap the button to save your new Z-offset permanently. This triggers a SAVE_CONFIG command and stores your settings.

⚠️ Don't skip this step! If you don't save, your adjustments will be lost on the next print.

Tips for Success

  • Make small adjustments: Babystepping works in small increments (usually 0.01-0.025mm). Don't over-adjust.
  • Watch the first few lines: You'll see the results of your adjustments within seconds.
  • Be patient: It's better to make gradual adjustments than to overshoot.
  • Good lighting helps: Position yourself where you can clearly see the first layer texture.
  • One test is usually enough: The calibration file is large enough to dial it in during a single print.

Verification

After saving your Z-offset:

  1. Print a small test object (e.g., a calibration cube or benchy)
  2. Check the first layer quality
  3. If it looks perfect, you're done! If not, repeat the fine-tuning process

Your Z-offset should now be perfectly dialed in for reliable, high-quality prints.

Alternative: Create Your Own Test File

If you prefer, you can create your own single-layer test print:

  1. Open your slicer (OrcaSlicer, PrusaSlicer, etc.)
  2. Import a large, flat model (e.g., a square or circle)
  3. Set layer height to your typical printing layer height (e.g., 0.2mm)
  4. Set the print to only 1 layer (adjust Z-height in slicer settings)
  5. Slice and export the G-code
  6. Upload to your printer and use it for fine-tuning

Troubleshooting

I adjusted too much and now it's worse

Solution: Home the printer and start a new test print. The adjustments aren't saved until you press "Save Z-Offset."

The "Save Z-Offset" button doesn't appear

Solution: You may not have made any adjustments during the print, or the printer didn't detect changes. You can manually save by running SAVE_CONFIG from the Console in Mainsail.

Different areas of the bed look different

Solution: This indicates your bed might not be perfect level. Return to bed leveling and re-level the bed, then redo Z-offset calibration.

Important Reminder

⚠️ After fine-tuning your Z-offset, do NOT re-level the bed unless absolutely necessary!

Re-leveling the bed changes its physical position, which invalidates your carefully calibrated Z-offset. If you must re-level (e.g., after moving the printer, hardware changes hitting the print bed), you may need to redo both coarse and fine Z-offset calibration.

Next Step: Input Shaping Calibration →