How to Print PETG Without Blobs?

Blobs and zits on PETG prints are a frustrating nightmare for intermediate 3D printers, ruining surface quality and wasting filament. Caused by oozing, overextrusion, or moisture, they plague even experienced users. This guide fixes that.

You'll learn step-by-step optimizations—from drying filament to tuning retraction—for flawless PETG prints. Expect cleaner surfaces, less waste, and pro-level results. Difficulty is intermediate, focusing on slicer tweaks and hardware checks.

Total tweaks take 30-60 minutes, plus test prints (1-2 hours). No major mods needed, but an enclosure helps.

▸What You'll Need

• •3D printer with heated bed (Ender 3 or similar)
• •PETG filament (1.75mm, quality brand)
• •Filament dryer or food dehydrator (optional but recommended)
• •Digital calipers for nozzle measurement
• •Slicer software (Cura, PrusaSlicer, or SuperSlicer)
• •All-metal hotend (required for reliable PETG; stock PTFE ones degrade)
• •Isopropyl alcohol (90%+) and brush for cleaning
• •Glue stick or PEI sheet for bed adhesion

Estimated Time: 45-90 minutes for setup + 1-2 hours for test prints Difficulty: intermediate

▸Step-by-Step Instructions

Step 1: Dry Your PETG Filament

PETG is highly hygroscopic, absorbing moisture that causes steam-induced blobs. Dry it first.

Heat filament at 65-70°C for 4-6 hours in a dryer or oven. Success: Filament feels dry, prints without popping sounds.

Why it matters: Wet PETG oozes more, creating blobs on layers.

💡 Tips:

• •Store in airtight bag with desiccant post-drying.

⚠️ Warnings:

• •Never exceed 80°C or filament softens.

Step 2: Install or Verify All-Metal Hotend

PTFE-lined hotends degrade at PETG temps (230°C+), causing clogs and blobs. Use all-metal.

Disassemble, replace with V6-style hotend. Heat to 250°C, push filament—should extrude smoothly.

Success: No PTFE degradation smell, consistent flow.

💡 Tips:

• •Micro Swiss hotends excel for PETG.

⚠️ Warnings:

• •Avoid stock Ender hotends above 240°C.

Step 3: Calibrate Extruder E-Steps

Overextrusion leads to blobs. Measure 100mm filament, extrude 100mm via G-code (G1 E100 F100), adjust steps/mm.

Formula: New steps = old * (100 / extruded). Update firmware or slicer. Success: Exactly 100mm extruded.

Why: Precise extrusion prevents excess material buildup.

💡 Tips:

• •Use 0.4mm nozzle standard.

Step 4: Tune Hotend and Bed Temperature

Too hot = oozing blobs. Start nozzle 235°C, bed 75°C. Print temp tower.

Optimal: 230-245°C nozzle (brand-specific), 70-80°C bed. Success: Smooth layers, no stringing/blobs.

Test: Print calibration cube, inspect corners.

💡 Tips:

• •eSun PETG likes 240°C.

⚠️ Warnings:

• •Too low causes under-extrusion.

Step 5: Optimize Retraction Settings

Oozing during travel causes blobs. In slicer: Retract 6-8mm at 40-60mm/s (direct drive: 1-2mm).

Enable Z-hop 0.2mm. Print retraction tower. Success: No strings or blobs on travels.

Why: Pulls filament back, minimizing drip.

💡 Tips:

• •Combing mode 'All' reduces travels.

Step 6: Adjust Print Speed and Cooling

High speeds amplify blobs. Set 40-50mm/s outer walls, 30% fan (PETG hates full cooling).

Slow first layer to 20mm/s. Success: Even layer heights, matte finish without warping.

Balance: Speed vs quality.

💡 Tips:

• •Bridge fan 100% sparingly.

⚠️ Warnings:

• •

  60mm/s risks underextrusion.

Step 7: Level Bed and Improve Adhesion

Uneven bed causes first-layer blobs. Auto-level or paper-test mesh.

Apply glue stick thinly. Success: Elephant's foot minimal, strong adhesion.

Why: Prevents lifting/extrusion issues.

💡 Tips:

• •PEI sheets grip PETG best.

Step 8: Enable Coasting and Test Print

Coasting stops extrusion before end, reducing blobs. Slicer: 0.2mm coast, 0.2mm wipe.

Print large model (Benchy). Inspect: Blob-free surfaces.

Iterate: Tweak based on results.

💡 Tips:

• •Use linear advance if Klipper.

▸Pro Tips

• •Use enclosure for stable temps—reduces warping/blobs by 80%.
• •Print in draft mode first to dial settings fast.
• •Capricorn XS tubing improves retraction reliability.
• •Monitor first 10 layers closely—fix early.
• •Store settings as PETG profile in slicer.
• •Slower infill (30mm/s) minimizes internal blobs.
• •Clean nozzle every 5kg PETG with cold pull.

▸Common Mistakes to Avoid

• •Skipping drying: Leads to steam blobs—always dry overnight.
• •High retraction speed (>70mm/s): Causes grinding—cap at 60mm/s.
• •Full fan cooling: Cracks PETG—keep under 50%.
• •Dirty nozzle: Accumulates residue, blobs everywhere—cold pull weekly.
• •Ignoring direct drive: Bowden tubes need 2x retraction distance.

▸Troubleshooting

Problem: Blobs persist on top layers

Solution: Increase coasting to 0.4mm or add wipe tower. Check overextrusion.

Problem: Stringy blobs during travel

Solution: Boost retraction distance +2mm, lower temp 5°C.

Problem: First-layer blobs

Solution: Re-level bed, thin glue layer, slow to 15mm/s.

Problem: Random blobs mid-print

Solution: Dry filament again, check for partial clogs with cold pull.

eSUN PETG Filament 1.75mm 1KG

Low-ooze formula with consistent diameter reduces blobs out-of-box.

Best for: Daily PETG printing for functional parts.

Price Range: $23.99

Micro Swiss All Metal Hotend Kit for Ender 3

Handles 250°C+ without degradation, essential for clean PETG flow.

Best for: Upgrading stock hotends prone to blobs.

Price Range: $49.99

SUNLU FilaDryer S2 Filament Dryer

Efficiently dries PETG in 4 hours, eliminating moisture blobs.

Best for: Hygroscopic filaments in humid environments.

Price Range: $59.99

Capricorn XS PTFE Tube 2M

Low-friction tube improves retraction speed, cuts stringing/blobs.

Best for: Bowden setups for precise PETG control.

Price Range: $14.99

Creality Ender 3 Enclosure

Maintains stable temps, preventing thermal expansion blobs.

Best for: Open-frame printers in drafty rooms.

Price Range: $99.99