Mystery Collision Events  

Mike Loyd
New Member

I have starter to have mystery collisions detected by my MK3s. I am at Firmware version 3.9.1-3518. I am regularly printing 14 to 20 hour print jobs 2 or 3 times a week with few issues other than user error. However I have had 5 failures in a row on a new print job with "Collision Detected" as the displayed fault. I would look at the print job but it is just a simple box so I have a hard time believing it could be a bad job. I have inspected the print and see no visible evidence to support the error. I have noticed a new vibration during my prints and wonder if I could have a bearing going bad. I have jogged all my Axis and find no obvious signs of bearing issues or otherwise.

Does anyone have alternate theories or things I should look at? I hate to break it all the way down but I guess that's the next step and to inspect every component.



Posted : 17/11/2020 1:52 am
Active Member

The main thing that helped me with mystery collisions was turning off the collision detection. Later, I put grease on the rails, and I suspect that would might have fixed it also.

Posted : 17/11/2020 2:42 am
Illustrious Member

A photo of the part where collisions were/are happening is a good idea. Sometimes collisions are real. Though, more often they are bearing seizure. 

And - while turning off collision detection makes that specific issue go away, the collisions continue to happen and will eventually cause more serious problems like layer shift, or knocking the part off the bed and blobs of doom.  CD is sort of like ABS brakes on a car. Sure, ABS can trigger when conditions are slippery, but should you disable the ABS, it won't really alter the fact the conditions are not good and you will still probably slip and slide into what it was you were braking for in the first place. 

And run the BELT TEST routine, see how far the numbers have changed since last run. If they are going down, your bearings are probably dry. Ignore the "belt test" part ... the numbers only indicate friction the motors must overcome to move the axis. Nothing to do with actual belt tension. 

Posted : 17/11/2020 3:55 am
Mike Loyd
New Member

I had not considered disabling collision detection and do agree it would likely get me past the current issue but without locating the root cause I will have only masked the issue. But please don't take that reply as lack of appreciation for your suggestion. 

I did not think of running the Belt Test. I will make sure to do that later today. 

Update on the issue is that I started thinking about why would I was not willing to test to see if the Job file was the issue so I started a new Job last night. This morning it was 8 hours into the 19 hour job and still running uninterrupted. I will rebuild the job that was having issues. I also notice that the new noise I was hearing was also no longer detectable. Makes me wonder if something in the Job file was the root cause after all.

Thank you for the comments!

Posted : 17/11/2020 5:54 pm

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