Blobs and Zits
Diagnose surface blobs with dry filament, stock profiles, flow and Pressure Advance calibration, and checks after tool changes.
Small raised dots on a wall often appear where a perimeter starts or ends. A vertical line of dots usually follows the Z-seam; scattered blobs can follow travel moves or tool changes. Locate the defect before changing retraction.
Identify the Pattern
| What you see | Start with |
|---|---|
| A raised dot at the same position on every layer | Seam location, Pressure Advance, and restart settings |
| Rough walls and excess material across the top as well | Over-Extrusion |
| Threads with deposits where travel ends | Stringing and Oozing |
| A blob after switching heads | The tool-change check below |
| Plastic collecting around the heater block | Hotend inspection rather than seam tuning |
1. Establish a Repeatable Baseline
- Dry the filament using Filament Drying.
- Select the stock printer, nozzle, and material profiles matching the job. Save a copy before editing.
- Print a small model with a straight wall and an identifiable seam. Keep orientation and layer height unchanged for comparisons.
- Check the slicer preview: note where perimeters begin, travel ends, and the active head changes.
- Photograph the seam and a wall away from it. If only the seam is raised, avoid reducing the whole print's flow just to hide that spot.
2. Check Retraction and Restart Changes
Compare the filament profile and any edited retraction macros with stock settings. Pay particular attention to extra material added when extrusion restarts. Restore a changed setting and repeat the same print before making another adjustment.
For V4 tool-change settings, open Web Interface > Macros > System > Settings > Printing > Tool Change Retraction, choose the tool, and set Retraction to 5 mm and Extrusion to 10 mm to restore firmware defaults. Repeat for the other tool if needed; see Tool Change Retraction. Ordinary travel retraction uses the matching slicer profile's values. Verify the macro and defaults separately on V2/V3.
With a supported material and unchanged profile, start with drying and calibration instead of automatically increasing retraction. For a different material, especially one with additives or different flow behavior, use a separate profile.
3. Calibrate the Material
Use Material Tuning in its stated order: temperature, Pressure Advance, then flow. The supplied tests require dry filament and a 0.4 mm nozzle; follow that guide's instructions if your production nozzle differs.
Inspect the Pressure Advance test for a seam without a bulge or gap, while checking that corners remain well formed. Too much compensation can exchange a raised seam for missing extrusion.
Save the result through the guide's Save to Slicer procedure. Record the material, nozzle diameter, nozzle type, and tested head alongside the values. Do not assume a result from another material or nozzle transfers unchanged.
4. Check Blobs After Tool Changes
For defects that appear only when both heads print in alternation:
- Observe a tool change from outside the motion area. Note whether material remains on the returning nozzle after heating and cleaning.
- Check the profile's Prime Tower option for that print mode.
- Enable the tower when supported, slice again, and confirm in the preview that the returning head visits it before the model.
- Repeat a short two-head job and inspect the first lines after each change.
If the tower prints cleanly but the model still has seam blobs, continue with Pressure Advance and restart checks.
5. Place the Seam
After correcting excess material, use seam position or seam painting to place the remaining seam on a less visible edge. Moving it does not remove excess extrusion. Compare wipe settings with the stock profile before adjusting them.
Verify the Result
Repeat the original test with the saved profile. The seam should have no raised deposits or restart gaps, and the wall should remain continuous. For a two-head job, verify several changes in both directions.
Record the Diagnostic Results
Keep a seam close-up and a full-part photo with the slicer project, material and nozzle details, and test settings. Record whether deposits follow every perimeter or only tool changes. These details make repeat tests comparable and help support investigate an unresolved defect.
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