Okay, this is the first solidoodle hack, and the simplest one.
solidoodle is a quite affordable 3d printer I got myself a few weeks ago. And the biggest problem it has – Z axis wobble. Quite bad even when printing at .35 mm layer hight. That was pretty bad, since it also made printing at .1 mm hight impossible, and some layers broke off easily.
Since I’m not a big mechanics engineer and my knowledge is limited by a few basic university courses quite a while ago, I had consulted my father who has over 30 years of expertise in mechanical engineering for a hint. After brainstorming the whole thing for a while, the obvious thing was to completely replace and redesign Z axis screw, leaving only the stepper motor from the original construction. Something that couldn’t be done really fast, especially since most of hardware shops here are closed due to holidays till 10nth of January.
And I only needed a few 3d-printed things of a decent quality fast.
There was an existing solution at soliforum, that (from what it looks like) adds a second nut to the same axis. I was advised against it, since a second nut to the same screw is always a VERY bad idea, and eventually can cause Z axis jams.
Then, a very simple idea came to my mind very soon. I noticed that the period of the ‘artifacts’ is fixed. After remembering what factors can give Z axis positioning errors, the quickest and dirtiest solution possible was ready:
Adding a weight near the screw improves the printing quality drastically, as you can see in the photo at the very top of the post. There is a clearly visible border before and after I added the weight. For now I secured the weight on the bed mount, close to the screw to get reasonable quality.
P.S. Removing the top cover also affects print quality, and you get more artifacts in Z positioning, but that is absolutely required to avoid filament jams, so I think of making an alternate cover with a spool holder above the extruder head.
P.P.S. Do not order the top cover from the solidoodle guys. It presses filament over the extruder head and causes occasional jams for me.