Print Extrusion Problem

I'm printing with a Mendel i2 using Pronterface and Skeinforge.

Printing the test objects (e.g. 20mm box, 50mm tower, etc) is fine.

However when I print other objects, I get strange behaviour in the first few layers. I've attached a photo showing the early stages of a print.

It's as if the filament is coming out in bursts or the print is being scuffed in some way.

Any suggestions would be greatly appreciated.

Thanks.

James.

Nice picture. Had wrestled with this issue in the very near past. Ended up being a combination of several things for my edition of this problem: 1) Nozzle to platen gap was increasing when the cruft started happening (leveled platen to nozzle all over the bed after both had soaked at operating temp for 1/2 hr at a tight 0.1 mm); 2) heat bed was coming on and snarfing the power supply just enough to mess up the print for a while (two supplies now - one for the printer, one for the bed); 3) Excessive moisture in PLA filament (baked in slow 160 deg oven until warm and now keeping in silica gel when in storage).

It was eliminate one issue, the others then were allowed to show up and get eliminated as well. Just as an aside, I use alcohol cleaned glass with a light layer of Elmer's purple gluestick to help with the sticking of the PLA to the glass.

Hope this gives you a starting point.