How to avoid nozzle from hitting the model?

Question

When printing objects higher than approximately 8-10 cm, sometimes nozzle hits the printed model and knocks over it. After 7-8 hours of printing that's really annoying. I'm using Creality Ender 3 Pro with Ultimaker Cura. How can I avoid this problem?

As a note; it happens with thick, wide models without support structure too. I'm using Ender 3 Pro's stock magnetic bed.

Here are some photos of printed model.

I use Esun PLA+, the part was on baseplate without any loss of contact. It was like one layer missed its coordinates and then all corrupted.

I think it's not related with bed adhesion because for example for this model, it didn't knock over the model.

There is no roof for the model, I think it doesn't need any support structure. Here you can see the expected finished one:

Answer 1

It seems the problem was because of Z-axis leveling (level of the X-axis), I found out that the right side was more than 3-4 mm below the left side when the Z-axis height exceeds around 8-10 cm. Below 8-10 cm, the two sides were even. I calibrated the X-axis by turning the eccentric nuts of the wheels and tighten them. I will try printing soon with some test objects.

Answer 2

There are options in Cura to avoid that the extruder hovers over printed parts when traveling. There is also an option to lift Z axis while traveling. Those options are hidden by default. You can only enable them in advanced settings mode.

Answer 3

There is a clear scar in the print that looks like the print head has hit it. The scar is about 1/3 of the way up the straight return segment on the right side of the photo.

The OP has provided enough information to show that it isn't an overhang or bridging problem.

I don't see any cracks in the print where part of it may have separated and bent upwards. I accept the OP's statement that the item is well attached to the bed.

What problems could there be?

The printer may have a Z-axis problem at that height. Perhaps it exceeds the maximum Z-height, or perhaps there is some obstruction or debris in a lead screw that is preventing it from freely moving above that height. The obstruction could be a cable that is too tight or an errant tie-wrap that hits something, or almost anything that interferes with motion at that height.

There is always the possibility of a bad wire (such as to the nozzle heater) that causes problems when the height reaches a critical level.

There may be a parameter change in the slicing software that is set for that height (or layer count). There shouldn't be, but a default profile may have been changed.