Extrusion flow

Hi, I have my RepRepPro Mendel for a week now, trying to get good quality prints, (very) slowly improving (still a long way to go). On some issues, plastic flow in particular, I find I could use some help, it will be greatly appreciated.

1. I can't get a consistent flow. After starting a thread, for the first 30mm of extrusion (roughly) flow seems ok (I get good solid walls here) - but for the next 30mm or so there is almost nothing (or much less) coming out. Most noticeable on perimeters, where I get thinner / weaker / messy / saggy walls - it happens consistently in same spots. Also noticeable on infill where I get (much) thinner or missing patches. I made sure my hot-end is clean, sliding the filament down the tube goes without impediment, extruding hot plastic by hand works nicely. I tried high and low (and none) retractions, lowered the feed-rate, fiddled with Oozebane, Dwindle, higher / lower temperatures, tightened the hobbed gear, etc - I must have missed the right settings. Any advice please ?
2. I observe the infill pattern, high solidity - the filament should be put with constant distance between adjacent lines. My infill lines come in noticeable batches - a pack of denser (closer together) lines (for a good 2mm in the X direction), then some wider apart (1mm or so in the X direction) - so I get a pattern: dense, loose, dense, loose, ... My thinking: maybe some impediments on the X axis prevents the X motor to maintain constant speed. I will check that, but some advice would be great.

Edited 2 time(s). Last edit at 03/09/2013 06:00AM by DRepBRo.

Do you have any pictures of the results?
That makes it easier to see what is going on.
May also want to try Slic3r or Kisslicer, settings are a little easier out of the box.

Thanks for responding. Unfortunately I only have a phone camera so the image quality is very bad. Nonetheless, something can be seen. It's the first layer of the front panel of Black Nightmare Puzzle Box ~ ( The irony ! ). I've added comments for the outer perimeter flow, the infill is also obviously very bad.

I have checked the X axis movement as I mentioned above- didn't find problems. I calibrated the E steps / mm, so that I get the length I requested - but in SkeinForge or Slic3r I have to crank up the flow rate or else barely anything gets extruded. The print in the picture was sliced with Slic3r; I had to up the extrusion multiplier at 1.9. Layer height is 0.35 + 130% for the 1st layer. I would like to use Slic3r but I get better prints with SkeinForge.

Since I started this thread, I will post an update on the issue. Well, I guess I never get to choose how to learn something - I eventually just get there taking only the bumpiest of all possible paths. So I found out I didn't secure the big extrusion gear with the small bearing that holds it firm. That's it.

It sounds to me like the stepper driver is incorrectly set for the extruder. If you have the amps turned up too much the driver will shut down for a short time so it can recover and can be a very short cycle that is hard to notice. This will give you a pulsed output that will result in a lowered filament output like you are describing. The same can happen if the stepper driver gets too hot due to overload. Has it got a heat-sink and a fan to keep it cool?

Thank you for replying. The issue is resolved now. Like I mentioned in my previous update, I didn't build the big extruding gear mechanism properly. The small bearing wasn't in place to keep the big gear steady enough. Once I installed the small bearing the plastic flow became consistent.