Stretch marks on my prints

[Sungod3000]

Hi,

I`ve been getting my printer under control lately and fixing most issues, but one is persistent.

Every 1.5 layers, the pitch of the laed screw, the outside perimeter curls up and doesn't bond with the layer below but it only happens on longer straight part of the print. Around corners the stacking of the layer is normal.
What is especially interesting is, that if i slow down the print below 20mm/s the gaps become smaller, so there is an interaction with the extrusion.

Any ideas?

Here some pics.
http://www.flickr.com/photos/1141765...7639695708276/

[Geoff]

looks like you are melting your plastic too hot, that happens to me when I run it too high. Are you hearing small popping or crackling sounds when it extrudes?

[Sungod3000]

I thought about that and tested a range of 180-220C, no cracking, no bubbles, no dirt in the nozzle. I also tested with 2 different materials. No change.
I imagine if it would be a heat thing or systematic extrusion error I would see gaps randomly spaced through the whole print. Not just on long lanes and ever 1.5mm.
So there must be some weird interaction between the lead screw system and the extrusion. I ordered a new lead screw with fine thread but I still have not the slightest idea what the interaction is.

[Kingoddball]

Odd. I had similar stretch marks (much worse)
It was because my filament was not rolling freely.

Two Reasons;
One: Hobbed Bolt was too tight and fighting and Spool was not freely spinning, it has to be pulled.
Two: Too hot. But my main issue was the spool.

To test, just cut 30cm off and have it loaded without spool.

[properrhino]

Hi Guys,
I'm facing 'stretch marks' too. (Best descriptive name by the way!)
Going to try your solutions. Do mention if they worked out for you guys.
I've attached images of whats happeneing to my prints, the image on the left was taken out a few months ago, now the same print is eeeky.
Any advice at this point would be great... I'm on a bfb3000 machine. Printing at 210temp
IMG_5161.jpgIMG_5164.jpg