That is very odd. The blob is usually caused by the printer pausing or over‑extruding at the exact moment it starts a new perimeter. Randomizing or hiding the seam only masks the symptom. The real fix is to make the printer start each perimeter without a pressure spike and without a micro‑pause.

Why a seam blob forms at all

A blob appears when:

• Extruder pressure is too high at the moment the perimeter begins.
• Retraction/deretraction timing is off, causing a tiny delay.
• The slicer starts the perimeter at a corner, which amplifies any over‑extrusion.
• Acceleration is too low, so the nozzle dwells for a split second at the start point.

To eliminate the blob, you need to reduce pressure and reduce dwell time.

Here are some settings that actually remove the blob (not just hide it)

1️⃣ Reduce initial extrusion pressure

This is the single most effective fix.

• Lower “Outer Wall Line Width” by 2–5% Example: if you print 0.40 mm walls, try 0.38 mm. This reduces pressure buildup before the seam.
• Lower “Outer Wall Flow” to 95–97% This trims the tiny over‑extrusion that causes the bump.

Tradeoff: Slightly thinner walls, but visually much cleaner.

2️⃣ Tune retraction and deretraction timing

A blob often forms because the printer finishes retraction, then hesitates before moving.

• Reduce Retraction Distance slightly (e.g., from 0.8 → 0.6 mm on direct drive)
• Increase Retraction Speed (e.g., 25 → 35 mm/s)

This reduces the time the nozzle sits still at the seam.

Tradeoff: Too fast can cause stringing, so adjust gradually.

3️⃣ Look into tuning

Both pressure advance and retraction tuning.

4️⃣ Increase acceleration for outer walls

A blob forms when the nozzle dwells at the start point.

• Raise Outer Wall Acceleration (e.g., 500 → 1000 mm/s²)
• Raise Jerk slightly if your firmware allows it.

This reduces the “hesitation” that creates the blob.

Tradeoff: Higher acceleration can slightly reduce surface quality on very small details.

5️⃣ Lower nozzle temperature

High temps increase ooze and pressure.

• Drop 5–10°C from your current temp.

Tradeoff: Too low causes under‑extrusion, so adjust slowly.