Wonky first and last 4 layers or so.

[ExplodedZombie]

After a long wait for the new cartridge thermistor for my E3D V6, I finally got a cube printed. I'm not sure what I did to my printer, but the results seem worse than before. First, the bottom 3-4 layers start out fine, then the whole cube shifts. It seems to print the rest of the cube pretty straight, then the last 3-4 layers shift BACK to the original position for the bottom 4 layers. At least that's what it looks like. Also, the top of the print seems to be lifting up at the corners slightly.

Material: ABS - Matterhackers Black
Rostock Max V2 w/ E3d V6
Heat: 225
Bed: 90 (The bottom looks better than at >=95)

Could it be these settings? I thought maybe tension at first, but it seems like it's just the bottom and top 4 layers. Any assistance is greatly appreciated.

[img]http://i878.photobucket.com/albums/ab34 ... CUBE_1.jpg[/img]

[nebbian]

The main difference between those 4 layers and the rest of the print is that you're also printing top and bottom surfaces. Check to see what your extrusion width and speed is for that, vs infill. This results in changes to perimeter size due to the stored pressure in the bowden. I can't see the shift in your photo, but can see some lower wall cave-in. This is usually due to too high a bed temperature... except 90 seems fine to me.

[ExplodedZombie]

You're absolutely right about the lack of shift. I looked closer and realized that the bottom is definitely caving in. I will look into my settings and report back tonight. Thanks a lot!

Would you say that the bottom layers vs infill should be roughly the same? I think my infill is much faster. ~30% infill. The width is supposed to be 130% for the first layer.

[nebbian]

Are you using slic3r? Just be careful about using percentages for extrusion width, this is a percentage of the _layer height_. It makes absolutely no sense to anyone, but there you go. I set all my widths manually to actual mm widths, and then it behaves properly. I use 0.6mm first layer, then 0.4mm for all the other widths (0.3mm nozzle). For a 0.4mm nozzle then good values are 0.6 first, and 0.5 for everything else.

If your infill is a lot faster than perimeters then you get issues like this. Try setting all speeds to be the same and try again. Alternatively you can go down the rabbit hole of using "advance", which fiddles with extrusion to try to get the pressure on the nozzle the same and take out this sort of effect.

[ExplodedZombie]

I'm going to have to admit I have no idea how to switch to slic3r. I'm just using the Mattercontrol software with the settings it came with. I really wanted to get the thing printing before diving into all the crazy stuff. It's a 0.4mm nozzle so I'll try those settings. thank you.

[ExplodedZombie]

Okay there are two major things I am noticing now:
1. The heat bed starts shooting up in heat when the hot end gets close to it to print the first layer. It's holding at 90 and I had to turn it off when it suddenly rose up to 95 and didn't seem like it wanted to stop. Could be why the bottom layer looked collapsed.
2. The two front edges, left and right, are concave, bowing toward the center of the object. Could this mean the belt is too tight on the rear axis? You can just barely see it in the photo above. It's definitely there. The back edges are almost perfect straight. Below is a slightly better image.
[img]http://i878.photobucket.com/albums/ab345/bharris990/DSC_0123.jpg[/img]

I also tried to switch to Slic3r but the slicing failed on this 20mm cube...