ripple on ABS first layer

[jspiro]

I've gone through the print troubleshooting guide but can't seem to figure this one out. Whenever I print ABS, concentric or rect fill, 0.1 through 0.3, the first layer has a consistent ripple pattern with areas that are perfect and areas that are rippled. This is both in large and small parts, it doesn't seem related to length. It's on a freshly cleaned heated glass that was just coated for ABS -- almost perfectly flat.

This image is a 0.25 first layer. The scar on it suggests over-extrusion or under-retraction. I've tried reducing the the extrusion multiplier (down to 90%) and it doesn't seem to change anything at all, it always looks like this:


Using a Prusa i3 from Prusa himself (not some random kit). I have this problem in general, not just with S3D.

S3D settings
Process: http://shop.prusa3d.com/forum/download/file.php?id=533
Factory: https://dl.dropboxusercontent.com/u/331 ... ds.factory

[CompoundCarl]

I've seen this on several of my printers, and it is almost always caused by very small defects in the build surface. For example, leftover plastic or small bumps or scrapes. It doesn't take much to impact the extrusion on a 0.1mm layer, and unfortunately, once it happens, it seems to also affect areas around it.

So it's hard to fix unless you have a truly perfect bed to print on that was machined to very tight tolerances.

[jspiro]

What's odd though is I get the exact same pattern in multiple areas. It's like some resonant frequency. But only ABS, not PLA.

[MikeO]

If it's a resonance problem, you should see a big difference if you deposit the first layer at half the speed you're using now.

[billyd]

It's the build surface. The repeating pattern is probably from the manufacturing process.

[jspiro]

MikeO, good point, I'll try a slower speed and see if it affects the pattern.

billyd: It isn't. I can print the same circle in four places and each has the exact same ripple effect. It's like a fingerprint. And ABS only.