Intermittent Bed/Z Axis crashing into Extruder.

When the Bed is leveling the Z axis at startup the bed will intermittently crash into the extruder in a specific spot in the process. It will start fine in the front right corner then move to the second point and that is also fine. When it reaches the 3rd spot about 6in from the leveling start point the bed will crash into the extruder.

So after reading some of the tips here is what I see going on....

When I do the suggested IR tests the IR limits seems to work fine... But when observing the leveling it flashes red in the FIRST and SECOND spots but when it crashes it does not flash Red before the crash.

The bed was leveled bla bla bla. It crashes in this ONE SPECIFIC SPOT on the bed, it does not do it all the time maybe a one out of three, it never did it out of the box, this started about a week ago. I have wiped off the IR sensors (a suggestion) I at first thought it was from sending a job from curia (the first time I used it) but it really does not matter if it is Curia or the job is started on the printer it just likes to make a divot in the print bed every now and then.
I read one of the posts says you can turn off leveling but there was no how to do it.
I'm pretty happy that the bed is level I run offset and the bed leveling wizards before prints and it has not changed much its always around 6.2 or 6.3 since out of the box and doing the fine tune does not change it much either.

All my prints have turned out awesome I even printed an MRI/CT scan of my skull full scale and everything has been great till I went to print some simple stuff and it made a divot in the print bed!! LOL!! And it now every few prints wants to crash at this one particular point.

Any Suggestions would be great.........
Maybe move your stuff to the store room....

 

I'm old school and writing extra gcode and whacking the unwanted gcode G29 will work for me.
Is there a list of the G codes specific to the unit?? I've text editor looked at the files the printer and other programs generate in Gcode it looks to be about the same as the code I have used for 20+ years on my milling machines and lathes with codes that I already know but there are other codes I have NO F'n Idea what they are and I'm hesitant to play with them.

Basically I print by using the control interface on the printer to run the GCO file/or slice it or having Octoprint upload and/or run the GCO file.
I originally thought it was the Curia program causing the problem (That is when this started) the first time I used it. But it happens using the printers slicer now or a slicer on a computer.

 

I like your theory its kinda my thinking..
When doing the IR tests I notice when the paper is moved too close to the sensor the red light goes out if you hold it in a narrow range it will illuminate constantly outside that range (too close too far) nothing.

At first I thought there might be a slight warp in that area of the bed I did check it with some parallels there is no optically obvious dip in the bed the other thing would be software not bringing it up/down enough and outside the range of the sensor and when it gets to "That spot" it screws up.

FWIW since I wacked G29 the last two small prints went without a hitch.....
We will see as I have some large stuff to print on Monday!
Like I said I check the Z before any print and the bed tilt also so there should be no worries or reason for the machine to "check the bed" anyway.

The machine prints great heck I did my own Skull from a CT scan DICOM file how cool is that?? Very I would say!!...
;-)
Attached is a photo.

Thanks for the input!!
-Joe

 

Great stuff!!

I see a couple things I'd like to ADD to certain prints.

Thanks again Mark

and
Waldo also!!