Just to clarify, so that people do not get the wrong idea about the safety mechanisms…
The built in safety devices do not detect if the head is about to hit something.
There are not any proximity sensors on the device to detect if something is in the path of the motion components.
There is an accelerometer built into the head, but it currently does not stop the device if the head impacts an object. You can see that this is the case by the many posts about the head impacting the front right side during prints. Here’s a video of it happening on my machine.