Wavy lines on 1st layer only

I'm getting wavy lines on the first layer only in both the x and y direction identically. The first layer is 0.4 mm with a 0.4 mm tip. I've tried changing the Z offset all the way from -1.2 to 0.5 mm. I've tried changing the hot end leveling the heated bed. None of these changes affected the wavy lines. The waves have about a 1 mm period. The printer is a German RipRap. The material is ABS. The heated bed is 110 C. I've tried the hot end at 220 C and 240 C. So far, nothing has changed the waves.

Is it a CoreXY machine?

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Quote
dc42
Is it a CoreXY machine?

I assume he means German RepRap. Some of those machines look like an H-bot kind of machine, but indeed, I would also guess this artifact is a CoreXY artifact.

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http://www.marinusdebeer.nl/

You can't print a 0.4mm layer thickness with a 0.4mm nozzle. There is nothing to squash the molten plastic to the print surface. Layer thickness should be limited to no more than about 75% of nozzle diameter, and less, typically around 50%, is better.

You also can't print lines that are narrower than the nozzle diameter.

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]