PETG is a favorite among makers for its balance of durability, flexibility, and glossy finish. But when it comes to printing tall parts, even experienced users can encounter a frustrating issue — layer splitting. This common defect weakens the structure and ruins otherwise beautiful prints. To achieve tall, flawless PETG prints, you need to understand why splitting happens and how to control every variable that influences interlayer adhesion.
What is Layer Splitting in Tall PETG Prints?
Definition & How It Manifests
Layer splitting, also known as delamination, occurs when successive layers fail to bond properly. In PETG, this problem often appears as visible horizontal cracks, weak seams, or entire sections separating when the part cools or bends. The taller the print, the more visible and destructive these splits become — especially on models like vases, mechanical components, or vertical enclosures.
Why Tall Prints Exacerbate the Issue
Tall PETG prints are more vulnerable because of uneven heat distribution. As each new layer cools, internal stresses develop between the hotter top sections and the cooler, already-solidified base. The longer print duration also increases the filament’s exposure to moisture, which weakens bonding and causes bubbling or uneven extrusion.
Unique Challenges of PETG vs Other Materials
PETG sits between PLA and ABS in terms of strength and flexibility. It resists warping better than ABS, but because it’s less brittle than PLA, it demands higher extrusion temperatures to ensure good adhesion. However, those same high temperatures can lead to stringing or sagging — creating a delicate balance that becomes even harder to maintain in tall prints.
Pre-Print Preparation: Material & Printer Setup
Selecting the Right PETG Filament
Start with a high-quality, dimensionally consistent filament. Cheap or uneven PETG spools often contain moisture or additives that prevent layers from bonding tightly. Brands that specialize in PETG for large structural prints are preferable. Always store PETG in a dry, sealed container with desiccant.
Drying and Storage for Optimal PETG Performance
PETG easily absorbs moisture from the air, which leads to popping sounds during printing and visible bubbles between layers — both of which encourage splitting. Dry your filament for at least 4-6 hours at 65°C before printing. For long prints, consider a filament dryer box that keeps it dry throughout the process.
Ensuring Your Printer is Up to the Task
A stable printer is essential for tall structures. Even minor vibrations or Z-wobble can create micro-gaps between layers. Tighten belts, check frame stability, and ensure your nozzle is clean. Bed adhesion is the foundation of the print — if the base shifts, even slightly, the upper layers will split as tension builds.
Optimising Print Settings for Tall PETG Parts
Temperature – Nozzle and Bed
PETG typically prints best between 235°C and 250°C. For tall prints, slightly higher nozzle temperatures (around +5°C over standard) improve interlayer bonding. Keep the bed between 75°C and 85°C to reduce warping and help maintain thermal consistency across the print’s base.
Cooling & Fan Settings
Unlike PLA, PETG benefits from minimal fan cooling. Excessive airflow can cause rapid contraction between layers. Use 0–30% fan speed, and avoid sudden bursts of cooling during tall prints. If your print has overhangs, balance cooling by enabling gradual fan ramps rather than abrupt changes.
Layer Height and Wall Settings
Thinner layers improve adhesion since each layer melts more evenly into the previous one. Use a layer height between 0.16–0.24 mm. Increasing the wall count to at least three perimeters helps distribute mechanical stress evenly, strengthening the vertical structure.
Print Speed & Flow
Slowing the print speed enhances the time for each layer to fuse properly. Keep your speed around 40–50 mm/s for standard PETG and adjust flow to about 102–104% to ensure consistent extrusion. A bit of over-extrusion can significantly improve adhesion without compromising detail.
Reinforcement: Infill and Perimeters
For tall prints under load, consider denser infill (30–50%) with a grid or cubic pattern. Strong perimeters (at least 3 walls) and more top layers help resist internal stress, making the entire part more cohesive.
Retraction & Travel
PETG is stringy, but aggressive retraction leads to under-extrusion at the start of layers, weakening them. Keep retraction low (0.5–1.5 mm on direct drive, 3–5 mm on Bowden). Avoid unnecessary Z-hops to prevent cooling interruptions.
Environmental & Print-Specific Considerations
Ambient Temperature and Drafts
Temperature fluctuations around the printer can cause uneven cooling — one of the main culprits behind layer splitting. Enclose your printer or use a draft shield to maintain stable conditions.
Monitoring Warping and Lift-Off
If the base lifts even slightly, stress ripples upward. Use brims or rafts to improve adhesion and maintain consistent surface contact throughout the print.
Print Time and Moisture Control
Long print sessions mean your PETG spool is exposed for hours. If your filament starts absorbing moisture mid-print, layer adhesion will degrade. Always keep filament enclosed in a dryer or spool box.
Handling Thermal Expansion
As tall PETG prints cool, they contract unevenly. Avoid quick temperature drops. When the print finishes, let it cool gradually on the heated bed to prevent cracks forming during shrinkage.
Troubleshooting Common Causes
Signs of Layer Separation
Look for tiny gaps or dull lines forming horizontally in the print. This is the earliest sign of delamination. Catching it early allows you to adjust temperatures or fan settings mid-print.
Fixing Insufficient Inter-Layer Bonding
If layers look poorly fused, raise your nozzle temperature slightly and reduce fan speed. Also, slow down the print by 10–20%.
Dealing with Moisture Problems
If you notice bubbling or oozing, pause and dry your filament. Switching to a fresh, sealed spool often resolves mysterious splitting issues immediately.
Preventing Draft and Cooling Shocks
Printing in an enclosed environment stabilizes cooling and maintains better layer adhesion.
Design Strategies for Tall PETG Prints
Part Orientation
Design tall prints with the load direction in mind. Orient parts so that stress runs along the layer lines rather than across them.
Wall Thickness and Chamfers
Thicker walls and rounded corners distribute internal stress more effectively, reducing split formation.
Internal Reinforcements
Integrate ribs or structural supports within the CAD design to stiffen vertical sections.
Annealing
Controlled annealing post-print (around 80–90°C) can relieve internal tension and improve layer bonding in PETG.
Post-Print Practices & Final Checks
Cooling Safely
Never remove a tall PETG print immediately after completion. Let it cool gradually for at least 20–30 minutes on the build plate to prevent sudden layer stress.
Inspecting the Print
Gently flex or tap the print to detect any weak areas. Well-bonded PETG will feel uniform, while poor bonding produces hollow or “snappy” sounds.
Repairing Minor Splits
Small cracks can be fixed with PETG-compatible adhesives or by re-melting the area using a heat gun at low temperature.
Key Takeaways
To prevent layer splitting in tall PETG prints, maintain proper nozzle and bed temperatures, minimize cooling, ensure dry filament, and design with mechanical stress in mind. Consistency in setup, material quality, and environment are the ultimate pillars of strong, crack-free PETG printing.
By mastering these factors, you’ll produce tall PETG parts with professional durability and finish — proving that precision and preparation matter more than luck in achieving perfect prints.