Key Takeaways

  • Adjust layer height: Make sure your layer height is 20% to 75% of your nozzle diameter to ensure proper pressure and bonding1.
  • Increase print temperature: Raise your print temperature by 5°C increments until the filament melts and flows smoothly.
  • Adjust flow rate: Increase your flow rate to avoid under extrusion and ensure enough material is extruded for each layer.
  • Use the right nozzle and filament: Choose a nozzle size and filament type that match your print settings and quality requirements.
Cracking in Prints

Sometimes a print job will be progressing nicely with no apparent problems. You leave the room, and when you come back you see that your object has developed a split or crack along one of its sides at a point where everything seemed fine before.

Layer separation refers to a visible, unwanted, horizontal crack/split in a 3D printed object. It shows up as an unplanned thin slit across a 3D printed object, almost as though it has been sliced with a blade.

It’s sometimes called delamination, and happens when two layers don’t bind properly during printing. 

Gaps in layers look awful and dramatically weaken your print. They can also be especially common in ABS prints. We’ll advise on how to prevent this below.

What Causes Splitting or Cracking in my 3D Print?

splitting and cracking

Your printer makes an object by laying down layers of print material, with each new layer binds to the previous one.

Splitting occurs when one layer bonds inadequately with another layer, causing a separation between the layers. When this happens, as the object cools, a split or crack occurs between the two inadequately bonded layers.

Luckily there are a couple of things that you can do to prevent splitting from occurring when using good quality filament.

If you’re still experiencing similar issues with poor layer adhesion in PLA or other materials, it could be down to simply using a cheap or poor-quality grade filament. 

How to Solve Splitting or Cracking Layers in 3D Printing

Decrease Layer Height

In order for two layers of print material to bond, the print nozzle needs to apply exactly the right amount of pressure to the layer currently being laid down.

Too much pressure and the layer will move off to one side or smear. Too little pressure and the layer can’t adequately meld to the previous print layer. The result is a crack.

Keep in mind that your nozzle diameter affects layer height settings. Generally, a 3D printer’s nozzle can accommodate a layer height that is 25% to 75% of its diameter. That range ensures that the nozzle is pressing down enough on the material being extruded to adequately bond it to the previous layer.

Increase Print Temperature

If your print temperature is too low, the filament won’t fully melt and therefore can’t flow out freely out of the nozzle. Even the material that flows out will be “half baked” and won’t stick well to the previous printed layer. As it cools, it will shrink and pull away from the layer below it. The result is a split or crack.

To avoid this from happening, increase your print temperature in increments of 5°C. The slightly higher temperature melts the filament fully and faster, ensuring steady flow of material that bonds readily with other layers. As the object cools, it stays intact without any cracks forming. 

When your extruded layer bonds with the previous layer properly, both layers essentially cool as one object, thus avoiding the splitting that would otherwise occur. 

You may also want to play around with reduced cooling, to get a really good layer adhesion. 

Just be careful you don’t go too far and end up with any of the cooling-related issues mentioned earlier in this article. 

If you’re still experiencing splitting layers after this, you may need to print in an enclosed area to keep the ambient temperature higher. This will slow the cooling process and put less strain on the print as it contracts slower.

Many 3D printers come with a built in enclosure, but if yours does not you can make a simple DIY enclosure basically for free.

Adjust Flow Rate

Flow rate, or extrusion multiplier, controls how quickly filament is fed into the hot end.

Calibrating the flow rate can fix issues of under extrusion, which is a culprit in many cases of splitting. When the flow rate is too slow, not enough filament comes out of the nozzle. This leads to under extrusion and poor layer adhesion. Remember that under extrusion might also be caused by a low print speed or temperature.

But if  you suspect that your flow rate is low, try increasing it gradually by 5% and notice if there are any changes in your prints. Try not to go overboard with these increments because a flow rate of 115% is probably too high and will lead to over extrusion issues

To find your flow rate settings in Cura, go to: 

  1. Select “Custom” mode in the settings panel.
  2. Right-click and click “Manage setting visibility…”
  3. Select “Check All” 
  4. Go to “Material” settings, select “Flow” and raise the percentage from the default 100%.

Use the Right Nozzle

You can prevent splitting or cracking by picking the right nozzle size. We know that smaller nozzles generally allow for high print detail because they extrude thin, precise layers. 

But to avoid splitting problems, use a nozzle diameter wide enough to allow more material to flow onto the print bed. This will result in thicker, wider layers that have more surface area to stick together. 

In addition, regularly clean your nozzle because a clogged or dirty nozzle can lead to inconsistencies in extrusion, which can cause layer separation. Over time, dust and filament debris can collect at the tip of your nozzle and cause a partial blockage. As a result, less filament will pass out of the nozzle and you’ll get thin layers that can’t bond together, creating splits in your final print.

To clean your nozzle, detach it from the printer and soak it in a cleaning solution for a couple of hours. You can use acetone for ABS and ethyl acetate for PLA. After taking the nozzle out of the solution, clean it with a thin needle or wire using a back and forth motion.

Quality Filament

Low-quality filament can cause layer separation in your 3D prints. Although readily available, the really cheap stuff tends to have an inconsistent diameter and plenty of impurities. These are a recipe for poor print finishes.

High quality filament, on the other hand, is made from first-rate raw materials that extrude consistently and bond strongly. But it’s not enough to get good quality filament–it’s also important to know how to keep it in top condition. 

Properly store your filament in airtight containers when you’re not printing. This is especially vital when it comes to PLA since it’s hygroscopic. Hygroscopic filaments are those that absorb moisture when left to stand in the air.

When filament absorbs moisture, it swells up in some areas and creates deformities such as splits in your prints. To fix “wet” filament, consider drying it in an oven, food dehydrator or filament dryer. 

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