Any idea what is causing this?  

Re: Any idea what is causing this?

Assuming you've had successful prints in the past and aren't having 1st layer issues, I always recommend slowing things down. Start the same print and immediately dial speeds way back (perhaps to 50%) using the front knob. If it prints successfully at slow speeds, you've eliminated a bunch of possible mechanical issues and can look at slicer configuration and tuning.

Is this by any chance the first print of this size you've done? One thing that strikes me is that the torn up chunks are solid infill. Prusa has selected very aggressive (200mm/s) solid infill speeds in Slic3rPE and their profiles for other slicers. On smaller prints, you'll never hit these speeds, so you may not have encountered this previously. That speed is too fast for some materials, and they may curl or adhere poorly at speed, causing this sort of problem. If slowing things down on the front panel works, I'd suggest knocking these speeds down a bit in your slicer. You could try bumping your temps up a bit, but that may cause problems with stringing and other features that work well now.

Alternately, you could tweak Print Settings->Speed->Autospeed (advanced)->Max volumetric speed or Filament Settings->Advanced->Print speed override->Max volumetric speed to 11.5mm^3/s. These set printer-wide and filament-specific limits on the amount of filament shoved through the extruder at any given time, taking into account nozzle size, extrusion width, layer height, speed, acceleration, jerk and no doubt other factors. Set these back and you don't have to do a lot of fiddling with individual speeds. They allow you to print up to your set maximum speeds, throttling as necessary so as not to exceed the capacity of the E3D V6 extruder. Slic3r will conform to the most restrictive of these settings. I've found this to be the best balance between speed and system limits.

Re: Any idea what is causing this?

That looks familiar.

Re: Any idea what is causing this?

That looks familiar.

Given from one of the other threads you're in it would seem that you've cracked the problem after 8 weeks, would you like to share?

Re: Any idea what is causing this?

are you slicing with Slic3r, using the correct profile for your printer?

make sure the bed is really clean, then try reducing the Live Z value

regards Joan

Re: Any idea what is causing this?

I had a print that kept doing that as well on one particular print, not on the base layer but about 10 layers in it went to hell, i tried everything i could think of for a few days and couldnt fix it, but every other print i did turned out fine.

I then re sliced it and it worked fine, i used the same setting as i did the first time i sliced it so i just chalked it up to a bad slice job, computers arnt perfect and sometimes output bad data. I would try to re slice it.

Re: Any idea what is causing this?

Thanks everyone. You've given me a lot of good things to try. To answer Bobstro's question, yes, this is the first very large item I've ever printed. It takes up nearly the whole bed. After i cleaned up after the mess, I immediately printed a smaller similar object with the exact same filament and it printed fine. I will try some of the suggestions you've all made and will report back .

Thanks, sincerely for your thoughtful replies.

Cory

Re: Any idea what is causing this?

Hi Cory,
i had a similar problem with a print 250mm x 145mm in PETg.
I had two fails until i gave the steel sheet a good wash with dish washing liquid (and a scrub-sponge) in the kitchen.
Maybe this is one of the problems with that print.
In the picture it seems like you have some kinde of debris in the front area of the steel sheet.
Greetings
Kai