over and under extrusion help

I'm having problems with layers bulging and not adhering. To me, it looks like an over and under extrusion problem and am not sure how to correct it. It seems like the base layer prints fine and aligns pretty good. The layers on top of the base layer get all crazy. Some extrusions are fatter than the perimeter of the base layer. Some are normal for several layers before a problem occurring. Some layers are smaller or wavy as if not extruding enough. The wavy layers break off easily so they are not adhering. When the extruder got to the top of the picture shown, it was not extruding a whole lot. I noticed the extruder wasn't pulling in filament. So I tightened the screws a bit and pushed the filament through. That got it working again, but the model was already jacked up. Many of the problems happen on a layer basis, and the whole layer may not necessarily be affected but parts of it. These are all in check:

- E steps were calculated
- filament was measured over about 15 feet and recently remeasured before this print
- extrusion multiplier set to 1 and not over extruding based on test parts
- solid parts without layers on top print fine; as soon as multilevel layers are introduced this shifting happens

Slic3r 1.2.9 was used. I noticed that after Slic3r does a bridge, it continues with the bridge settings for several layers before reverting to normal. The bridge extrusion multiplier is .9. PETG is being used.

Is my printer jacked up somewhere, or is Slic3r messed up? Please help.

what's your retraction setting in slicer

I have a Bowden drive with an E3dv6 hotend. Retraction is set a 2mm and 45mm/s. I've had the distance higher before, but I read a blog post or some article on E3D's website saying not to go beyond 2mm because the filament will get into the cool zone potentially causing issues.

So I've been doing a lot of tweaking and thought I'd share some results. I finally got this to print rather well. I'll share my settings in case anyone else is having a hard time with PETG. I'm usimg Maker Geek's brand. The spool says 260C, and I find that to be accurate. I've tried all sorts of speeds. These settimgs apply to Slic3r and to most extent S3D.

First, let's talk about coolimg. I leave this off unless it's repeat quick layers where a layer is under 5 seconds where fan can be 50-100 percent. For bridging I use 100% fan. I can't get Slic3r to turn on the fan for bridges, so I manually set cooling to turn the fan on 100% for the layer before the bridge layer. Then I turn it off after.

For retraction, I use 2.75mm at 60mm/s using a Bowden setup. I wipe on retraction. There is no extra length added. It seems to give the best results without holes from lack of filamemt due to a large retraction distance.

For speed, PETG prints Rather slow. You also have to manage soeeds to minimize stringing. I setup the following speeds in Slic3r:

Perimeters: 45mm/s
Small perimeters: 20mm/s
External perimeters: 75%
Infill: 45 mm/s
Solid infill: 80%
Top solid infill: 60%
Travel: 160 mm/s
First layer: 50%

If the small perimeter speed is too slow, you will get the fat layers I show in my pic. It happened here and other prints I did. I'm not sure why.

Bridging is interesting. In the above print it recognizes a less than 1mm gap as a bridge. So it was jackimg up the speeds or messing with extrusion than carries around the whole print. It could be a bug in Slic3r. So to fix it, I set the bridge speed to the small perimeter speed with a bridge extrusion multiplier of 1. That worked well. For regular bridging, I'm still messing woth it. 57mm/s print speed with a .9 bridge extrusion multiplier seems to be working well.

I hope someone else can benefit from this info.

Edited 1 time(s). Last edit at 04/26/2016 07:34PM by mlaustin66.