ABS (Acrylonitrile Butadiene Styrene) is a popular filament choice for its strength, durability, and heat resistance. However, it has one notorious downside: cracking and splitting during printing. If you have ever printed with ABS and watched layers separate or cracks form mid-print, you are not alone. This ultimate guide will walk you through why it happens and, more importantly, how to fix and prevent it.
Why ABS Prints Crack and Split
Understanding the causes of cracking is key to solving the problem. ABS behaves differently than PLA or PETG, mainly because it is sensitive to temperature fluctuations.
- Thermal contraction: ABS shrinks as it cools. If different layers cool at different rates, they pull apart, causing splits.
- Poor bed adhesion: If the first few layers do not stick properly to the bed, the print can warp, leading to stress and cracks in upper layers.
- Environmental factors: Drafts, cold air, and sudden temperature changes during printing cause rapid cooling and splitting.
- Incorrect printer settings: Low bed or nozzle temperatures, fast cooling fans, or poor layer bonding settings contribute significantly.
- Part design issues: Tall, thin, or sharp-cornered parts are more prone to splitting due to increased stress concentrations.
Knowing these causes helps you apply the right fixes.
Step 1: Control the Printing Environment
Use an Enclosure:
An enclosure is one of the most effective solutions for ABS. It traps heat around the print, preventing rapid cooling and protecting against external drafts. Even a simple DIY box made from acrylic panels or a cardboard enclosure can dramatically improve results.
Maintain Warm Ambient Temperature:
Ideally, the air inside the enclosure should stay around 40–50°C. This stable environment reduces thermal gradients that cause splitting.
Avoid Drafts and Airflow:
Turn off ceiling fans, close windows, and avoid air conditioners or vents blowing onto the printer during an ABS print.
By stabilizing the print environment, you allow ABS layers to cool uniformly, preventing cracks.
Step 2: Optimize Bed Adhesion
Use a Heated Bed:
ABS requires a heated bed to prevent warping and cracking. A bed temperature between 90–110°C is typical. Adjust slightly based on your printer and filament brand.
Choose the Right Surface:
Surfaces that work well with ABS include:
- PEI sheets
- Kapton tape
- ABS slurry (ABS dissolved in acetone spread thinly on the bed)
- Special ABS print surfaces designed for better adhesion
Enable a Brim or Raft:
Adding a brim (5–10 mm) around the model helps anchor the print to the bed. Rafts are even more effective for difficult prints but require post-processing to remove.
Level and Clean the Bed:
Perfect first layer adhesion is critical. Ensure your bed is leveled correctly and clean from oils or dust before starting a print.
Bed adhesion failures often lead to warping at the bottom and splits higher up, so starting strong is essential.
Step 3: Adjust Print Settings for ABS
Nozzle Temperature:
ABS usually prints between 220–260°C. Printing too cool results in weak layer bonding. If you notice splitting between layers, increasing the nozzle temperature by 5–10°C can often solve it.
Printing Speed:
Print slower for better adhesion between layers. Speeds between 30–50 mm/s are ideal for ABS. Faster printing does not allow layers to bond properly.
Layer Height:
Slightly thicker layers (around 0.2 mm or more) improve strength. Very thin layers can cool too quickly and lose adhesion strength.
Cooling Fan Settings:
Minimize cooling fans when printing ABS. Unlike PLA, ABS benefits from slow cooling. Keep fan speeds low (0–20%), especially for larger parts.
Proper tuning of these settings improves both strength and cosmetic quality.
Step 4: Design Models to Resist Cracking
Avoid Sharp Corners:
Sharp corners concentrate stress and often lead to cracks. Use fillets or chamfers to spread stress more evenly.
Increase Wall Thickness:
Thicker walls add structural strength, resisting internal stresses from shrinkage. Aim for at least 2–3 perimeters for functional ABS parts.
Add Support Structures:
Large flat surfaces can warp and crack easily. Use internal ribs or bracing structures in your model design to reduce stress points.
Orient the Model Correctly:
Printing tall objects vertically increases the chance of cracks because vertical layer bonds are weak. If possible, reorient the model to minimize vertical stress.
Good design practices can significantly reduce splitting risks, even without major printer changes.
Step 5: Post-Processing Techniques
Even if minor cracks appear, you can often salvage the print.
Acetone Welding:
Brush a small amount of acetone over cracks. ABS softens and melts slightly, allowing you to press the crack closed and fuse the part back together. Once dry, the repaired area will often be as strong as the surrounding material.
Heat Gun Treatment:
For small splits, carefully heating the print with a heat gun can sometimes soften and reflow the layers together. Caution is necessary to avoid overheating and deforming the model.
ABS Slurry Repair:
Mix a little ABS filament with acetone to create a paste. Apply this paste into cracks, allow it to dry, and sand it smooth for a clean repair.
These techniques can rescue prints without needing a full reprint.
Step 6: Consider Alternative Filaments
If persistent cracking continues despite all efforts, and environmental control is difficult, consider using alternatives:
- ASA (Acrylonitrile Styrene Acrylate): Similar to ABS but with better UV resistance and lower warping tendencies.
- ABS+ blends: Modified ABS with additives to improve layer bonding and reduce cracking.
These filaments print with similar settings but offer a more forgiving experience.
Common FAQs About ABS Cracking and Splitting
Why does my ABS print split in the middle?
Splitting typically happens where the part cools unevenly or where tall sections create stress. Improving enclosure warmth and increasing nozzle temperature usually helps.
Can you fix a cracked ABS print?
Yes, methods like acetone welding, heat gun smoothing, and using ABS slurry can repair cracks effectively without reprinting.
Should I use cooling fans with ABS?
Very little cooling fan use is recommended. High fan speeds cause ABS to cool too quickly, leading to splitting and weak prints.
Is it necessary to print ABS with an enclosure?
While small parts may succeed without it, an enclosure is highly recommended for reliable results, especially with larger models.
What bed temperature is best for ABS?
A bed temperature between 90–110°C is ideal. Warmer beds improve adhesion and minimize early-stage warping that leads to cracking later.
Conclusion
Cracking and splitting in ABS prints can be extremely frustrating, but they are entirely preventable with the right techniques. By controlling your environment, fine-tuning printer settings, designing smarter models, and understanding the material’s behavior, you can dramatically improve your ABS printing success. Whether you are creating strong functional parts or polished display models, applying these strategies will help you achieve durable, crack-free prints with ABS. Mastering ABS opens the door to high-performance parts that withstand heat, stress, and wear far better than many other common filaments.