Can I get rid of the seam completely?

Not fully on most models, because each layer has to start somewhere. You can hide it by placing it on a sharp corner or the back of the part, or reduce it with pressure advance, wipe and well-tuned retraction. Vase mode removes the seam on suitable single-wall models because the nozzle spirals upward continuously without stopping.

Why are blobs worse on small parts?

Small parts have short layers, so the nozzle changes layers, retracts and restarts very often, and there is little time for each layer to cool. That means more start points per centimeter of height and more chances for pressure errors. Printing several copies at once or adding a cooling pause with minimum layer time helps.

Do blobs mean my printer is broken?

Usually not. Blobs and zits are a tuning issue in most cases, related to seam settings, retraction and pressure. A failing part is more likely if blobs appeared suddenly with no setting change, which may indicate a partial clog, a worn nozzle or wet filament. Start with the slicer and filament before looking at hardware.

Blobs and zits: causes and how to fix it

What blobs and zits are and how to confirm them

Each layer has a start and an end point on the outer wall. When the nozzle stops extruding, retracts, travels and then starts again, the pressure inside the nozzle is not perfectly controlled. A little too much plastic leaves a bump, too little leaves a small gap. Lined up vertically these points form the seam; scattered, they look like zits.

Check the sliced preview with seams shown. If the bumps match seam positions or travel starts, the cause is retraction and pressure control. Random bumps all over the surface with crackling sounds during printing point to wet filament. Larger lumps that drag across the print come from oozing buildup on the nozzle.

It also helps to note whether each bump has a small dent or gap next to it. A bump followed by a gap usually means the nozzle overshoots on restart and then runs short, which is a pressure problem rather than a temperature one. Bumps without any gap, sitting on otherwise smooth walls, point more toward oozing during travel or extra restart material. Work through the fixes below one at a time and reprint the same small test, such as a 20 mm cylinder, so you can see which change made the difference.

Causes, most likely first

Seam placement set to random or shortest, scattering starts across visible faces.
Oozing and retraction settings that leave extra plastic at layer changes.
Pressure in the nozzle not compensated at the end of lines.
Temperature or flow too high.
Moisture in the filament.
Plastic buildup on the nozzle that drops onto the surface.

Fixes, cheapest and fastest first

1. Control seam placement

Set seam position to aligned, rear or sharpest corner so starts are hidden in a corner or the back of the part. Random seams spread zits around but make them smaller; it is a trade-off.

2. Tune retraction

Typical starting points: 0.5 to 2 mm for direct drive, 4 to 7 mm for Bowden, at 25 to 45 mm/s. Check "extra restart distance" or "retract extra" is zero; positive values add plastic at each restart.

3. Use wipe and coasting

Enable wipe on retraction so the nozzle moves along the wall while retracting. Coasting of about 0.1 to 0.3 mm stops extrusion slightly before the end of a loop. Use small values; too much leaves gaps.

4. Calibrate pressure advance or linear advance

If your firmware supports it, calibrate pressure advance with the built-in test pattern. Typical values are around 0.02 to 0.08 for direct drive and higher for Bowden. This reduces bulges at line ends and corners.

5. Lower temperature and verify flow

Drop 5 °C and check flow with a single-wall test so excess plastic is not the root cause.

6. Dry filament and clean the nozzle

Dry the spool if you hear popping. Wipe the nozzle with a brass brush when hot and consider a silicone sock to stop buildup.

Material notes

PLA: responds well to seam placement and modest retraction.
PETG: builds up on the nozzle and deposits blobs. Use a silicone sock, keep temperatures moderate and use Z hop if the nozzle drags.
ABS: small zits sand off easily; acetone vapor smoothing also hides them.
TPU: low retraction means more oozing at seams; accept a visible seam and place it in a corner.

Prevention checklist

Pick an aligned or rear seam for display parts.
Keep retraction in the normal range and extra restart at zero.
Calibrate pressure advance once per material.
Keep filament dry.
Clean the nozzle and use a silicone sock.
Avoid very high temperatures.

Blobs and zits